Hierarchies of Evidence

Hierarchies of Evidence are a tool employed by many advocates of Evidence-Based Medicine. They are used to appraise evidence from a range of sources, as well as to teach medical students about evidence and evidence appraisal. My PhD thesis concerns the variation in hierarchies defended, and the range of philosophical interpretations of those hierarchies. In order to complete this project, it is necessary to create and maintain a database of hierarchies of evidence.

This database was compiled by a systematic review of the medical literature conducted in three stages in 2011, 2017 and 2020. It is up-to-date as of 08/10/2020. Details of the systematic review can be found here.

This database is available here for the benefit of other researchers interested in Evidence-Based Medicine and hierarchies of evidence. Where possible, links are provided. Please contact me if you notice any broken links. If you know of any hierarchies not included in this list, please contact me. I am particularly interested in non-English hierarchies which are not available in English translation. The database currently only includes hierarchies available in English. For the purposes of this database, quite a broad selection criterion has been employed to maximise scope. The definition used here is:

“A procedure for making an inference about some epistemic property of the evidence provided by studies, or some epistemic relation which holds between the evidence provided by two or more studies, primarily based on a ranking of the design or methodology used in the studies.”

Note that some sources identify Campbell & Stanley (1963) or Cochrane (1972) as presenting the first evidence hierarchy. While these are both clearly important sources and had a strong influence on the development of early hierarchies, it is my judgment that neither contain a hierarchy as such. For more on whether Cochrane’s Effectiveness and Efficiency is the origin of evidence hierarchies see here, and for more on Campbell & Stanley’s work and other proto-hierarchies (including a hierarchy of sorts by Wright from 1912) see here.

1979Canadian Task ForceCMAJCanadian Task Force on the Periodic Health Examination. (1979) "The Periodic Health Examination". CMAJ 121 1193-1252"
1981AnonymousCMAJ(1981) “How to read clinical journals: IV. To determine etiology or causation”. CMAJ, 124, 985-990.
1986SackettChestSackett, D. L. (1986) “Rules of evidence and clinical recommendations on the use of antithrombotic agents”. Chest, 89(2 Suppl), 2S-3S.
1987LaForceJAMALaForce, F. M. (1987) “Immunizations, immunoprophylaxis, and chemoprophylaxis to prevent selected infections. US Preventive Services Task Force”. JAMA, 257(18), 2464-2470
1989SackettChestSackett, D. L. (1989) “Rules of evidence and clinical recommendations on the use of antithrombotic agents”. Chest, 95(2 Suppl), 2S-4S.
1992Cook et al.ChestCook, D. J., et al. (1992) “Rules of evidence and clinical recommendations on the use of antithrombotic agents”. Chest, 102(4 Suppl), 305S-311S
1992McGowan et al.Infectious DiseaseMcGowan, J.E. et al. (1992) “Guidelines for the use of systemic glucocorticosteroids in the management of selected infections”. Journal of Infectious Disease, 165, 1-13
1993Ogilvie et al.CMAJOgilvie, R. I., et al. (1993) “Report of the Canadian Hypertension Society Consensus Conference: 3. Pharmacologic treatment of essential hypertension”. CMAJ, 149(5), 575-584
1994Bigos et al.AHCRPBigos, S., Bowyer, O., & Braen, G. et al. (1994) Acute low back problems in adults. Clinical practice guideline. AHCPR Pub. No. 95–0643. Rockville (MD): US Department of Health and Human Services. Public Health Service, Agency for Health Care Policy and Research.
1994Canadian Task ForceCTFCanadian Task Force on the Periodic Health Examination, & Canada. Health Canada. (1994). The Canadian guide to clinical preventive health care. Canadian Government Pub Centre.
1994Gross et al.Clin Inf DisGross PA, Barrett TL, Dellinger P, Krause PJ et al. (1994) "Purpose of
Quality Standards for Infectious Diseases." Clinical Infectious Diseases. 18(3),
1994OxmanBMJOxman, A.D. (1994) "Checklists for review articles", in BMJ, 309(6955): 648-651
1995AnonymousBandolierAnonymous. (1995) “Evidence-Based Everything”. Bandolier, 12, 91-98
1995Byar/PiantadosiControlled Clinical TrialsPiantadosi, S. (1995). "David Byar as a teacher." Controlled Clinical Trials, 16 (4), p. 202 ~~ Byar's hierarchy is referenced by Olgin and Clarke but never published by Byar. Piantadosi published a version.
1995Guyatt et al.JAMAGuyatt, G. H., et al. (1995) “Users' guides to the medical literature. IX. A method for grading health care recommendations. Evidence-Based Medicine Working Group”. JAMA, 274(22), 1800-1804
1995OlkinJCEOlkin, I. (1995) "Statistical and theoretical considerations in meta-analysis". Journal of clinical epidemiology (0895-4356), 48 (1), p. 133. ~~ An expansion of Byar's hierarchy as published by Piantadosi.
1996Hadorn et al.JCEHadorn, D. C., Baker, D., Hodges, J. S., & Hicks, N. (1996). "Rating the quality of evidence for clinical practice guidelines." Journal of clinical epidemiology, 49(7), 749-754.
1997Evans et al.J clin oncolEvans, W. K., et al. (1997) “Lung cancer practice guidelines: lessons learned and issues addressed by the Ontario Lung Cancer Disease Site Group”. J Clin Oncol, 15(9), 3049-3059
1997GoldbloomJ clin oncolGoldbloom, R. (1997) "Weighing the Evidence: the Canadian Experience."
American Journal of Clinical Nutrition 65, pp.584S-586S
1997Granados et al.EUR-ASSESSGranados, A., Jonsson, E., Banta, H. D., Bero, L., Bonair, A., Cochet, M. C., … Espinas, J. A. (1997) "EUR-ASSESS Project Subgroup Report on Dissemination and Impact." International Journal of Technology Assessment in Health Care, 13(02), 220–286.
1997GrayGray, J.A. Muir. (1997) Evidence-Based Healthcare. NYC: Churchill-Livingstone
1997GreenhalghBMJGreenhalgh, T. (1997) “How to read a paper. Getting your bearings (deciding what the paper is about)”. BMJ, 315(7102), 243-246
1997/2001GreenhalghBMJGreenhalgh, Trisha. (1997) How to read a paper : the basics of evidence based medicine. London: BMJ Pub. Group ~~ Greenhalgh uses nearly-identical hierarchies in her book as in her paper, but to quite different effect.
1997Liddle, Williamson & IrwigNSW Pub Heal BullLiddle, J., Williamson, M., & Irwig, L. (1997) "Method for evaluating research and guideline evidence." New South Wales Public Health Bull, 8, 5.
1997Lloyd-SmithBJOTLloyd-Smith, W. (1997). "Evidence-based practice and occupational therapy." British Journal of Occupational Therapy, 60(11), 474-478.
1997/2000Van Tulder et al.Spinevan Tulder, M., et al. (2000) “Exercise therapy for low back pain: a systematic review within the framework of the cochrane collaboration back review group”. Spine (Phila Pa 1976), 25(21), 2784-2796
1998ClarkeBMJClarke, M.J. (1998) ‘Ovarian ablation in breast cancer, 1896 to 1998: milestones along hierarchy of evidence from case report to Cochrane Review’ BMJ, 317 (7167): 1246-8
1998Edwards, Russell & StottFam PractEdwards, A. G., Russell, I. T. & Stott, N. C. (1998) “Signal versus noise in the evidence base for medicine: an alternative to hierarchies of evidence?”. Fam Pract, 15(4), 319-322
1998McPeek et al.B. McPeek, H. Troidl, M.F. McKneally (1998) "Turning clinical problems into research studies", in: H. Troidl, M.F. McKneally, D.S. Mulder, A.S. Wechsler, B. McPeek, W.O. Spitzer (Eds.), Surgical Research. Basic Principles and Clinical Practice, 3rd ed., Springer, pp. 191–196.
1998Meltzer et al.CMAJMeltzer S, Leiter L, Daneman D, Gerstein HC, Yale J-F, Zinman B et al (1998) “Clinical Practice Guidelines for the Management of Diabetes in Canada.” CMAJ 159(8), pp.S1-S29.
1998Phillips et al.CEBMPhillips, R. et al. (1998) “Levels of Evidence”. Centre for Evidence-Based Medicine, www.cebm.net. ~~ no longer easily available online - pdf stored"
1999Australian NHMRCANHMRCAustralian National Health and Medical Research Council (ANHMRC). (1999) A Guide to the Development, Implementation and Evaluation of Clinical Practice Guidelines. Commonwealth of Australia: available at: http://www.health.gov.au/nhmrc/publicat/synopses/cp30syn.html"
1999BeckmannSem Thromb & HemoBeckmann, J. (1999, February). Basic aspects of risk-benefit analysis. In Seminars in thrombosis and hemostasis (Vol. 25, No. 01, pp. 89-95).
1999Chesson et al.SleepChesson, A. L., Jr., et al. (1999) “Practice parameters for the treatment of restless legs syndrome and periodic limb movement disorder. An American Academy of Sleep Medicine Report. Standards of Practice Committee of the American Academy of Sleep Medicine”. Sleep, 22(7), 961-968
1999Chestnut et al.AHCPRChestnut R.M., Carney N., Maynard H. et al (1999) “Rehabilitation for Traumatic Brain Injury.” Rockville (MD): Agency for Health Care Policy and Research (US). Evidence Reports/Technology Assessments, No. 2.
1999Hoogendoorn et al.Scand J Work Environ HealthHoogendoorn, W. E., et al. (1999) “Physical load during work and leisure time as risk factors for back pain”. Scand J Work Environ Health, 25(5), 387-403
1999McAlister et al.JAMAMcAlister, F. A., et al. (1999) “Users' Guides to the Medical Literature: XIX. Applying clinical trial results B. Guidelines for determining whether a drug is exerting (more than) a class effect”. JAMA, 282(14), 1371-1377
1999Shekelle et al.BMJShekelle, P. G., et al. (1999) “Clinical guidelines: developing guidelines”. BMJ, 318(7183), 593-596
1999WilkinsonTrans. Am Opthal. SocWilkinson, C.P. (1999) “Evidence Based Medicine Regarding the Prevention of Retinal Detachment.” Transactions of the American Ophthalmological Society. XCVII, 397-406.
2000American Heart AssociationAHAAmerican Heart Association (2000) “Part 1: Introduction to the International Guidelines 2000 for CPR and EEC: A Consensus on Science.” Circulation 102(Supplement 1): I1-I11.
2000Ariens et al.SJWEHAriens GAM, van Mechelen W, Bongers PM, Bouter LM, van der Wal G. (2000) “Physical risk factors for neck pain.” Scand J Work Environ Health, 26(1): pp.7-19
2000Bennett & BennettAus Occ Therapy JBennett, S., & Bennett, J. W. (2000) "The process of evidence‐based practice in occupational therapy: Informing clinical decisions." Australian Occupational Therapy Journal, 47(4), 171-180.
2000Briss et al.AM J Prev MedBriss, P. A., et al. (2000) “Developing an evidence-based Guide to Community Preventive Services--methods. The Task Force on Community Preventive Services”. Am J Prev Med, 18(1 Suppl), 35-43
2000EllisAdv NursingEllis, J. (2000). Sharing the evidence: clinical practice benchmarking to improve continuously the quality of care. Journal of advanced nursing, 32(1), 215-225.
2000Greer et al.Joint CommissionGreer, N., Mosser, G., Logan, G., & Halaas, G. W. (2000) “A Practical Approach to Evidence Grading.” The Joint Commission Journal on Quality Improvement, 26(12), 700–712.
2000Guyatt et al.JAMAGuyatt, G. H., et al. (2000) “Users' Guides to the Medical Literature: XXV. Evidence-based medicine: principles for applying the Users' Guides to patient care. Evidence-Based Medicine Working Group”. JAMA, 284(10), 1290-1296
2000Opie, Yusuf & KüblerProgr in Cardio DisOpie, L. H., Yusuf, S., & Kübler, W. (2000) "Current status of safety and efficacy of calcium channel blockers in cardiovascular diseases: a critical analysis based on 100 studies." Progress in cardiovascular diseases, 43(2), 171-196.
2000Roman, Silberzweig & SiuEff Clin PractRoman, S. H., Silberzweig, S. B. & Siu, A. L. (2000) “Grading the evidence for diabetes performance measures”. Eff Clin Pract, 3(2), 85-91
2000Sackett et al.EBMSackett, David L. (2000) Evidence-based medicine: how to practice and teach EBM (2nd ed.). Edinburgh: Churchill Livingstone
2000Weightman, Barker & LancasterHealth Evidence Bull. WalesWeightman A.L., Barker J., & Lancaster J. (2000) "A systematic approach to identifying the evidence. Project Methodology 3." Health Evidence Bulletins Wales. Cardiff: Department of Information Services, University of Wales College of Medicine
2001CravenEJ Onc NursingCraven, O. (2001) "Screening for colorectal cancer using the faecal occult blood test: a critical literature review." European Journal of Oncology Nursing, 5(4), 234-243.
2001Eccles, Freemantle & MasonEccles, M., Freemantle, N., & Mason, J. (2001) "Using systematic reviews in clinical guideline development." Systematic Reviews in Health Care: Meta-Analysis in Context, Second Edition, 400-409.
2001Harbour & MillerBMJHarbour, R. & Miller, J. (2001) “A new system for grading recommendations in evidence based guidelines”. BMJ, 323(7308), 334-336
2001Harris et al.Preventive Services Task ForceHarris, R. P., et al. (2001) “Current methods of the US Preventive Services Task Force: a review of the process”. Am J Prev Med, 20(3 Suppl), 21-35
2001HaynesACP J ClubHaynes, R. B. (2001) “Of studies, syntheses, synopses, and systems: the 4S evolution of services for finding current best evidence”. ACP J Club, 134(2), A11-13
2001JonasWJMJonas, W.B. (2001) ‘The evidence house: How to build an inclusive base for complementary medicine’, in Western Journal of Medicine, 175: (2) 79-80
2001Khan, Dinnes & KleijnenEJ Obst Gyn Rep BioKhan, Khalid S, Dinnes, Jacqueline & Kleijnen, Jos. (2001) “Systematic reviews to evaluate diagnostic tests”. European Journal of Obstetrics & Gynecology and Reproductive Biology, 95(1), 6-11
2001McAlister & SackettAm J MMcAlister, F. A., & Sackett, D. L. (2001) "Active-control equivalence trials and antihypertensive agents." American journal of medicine, 111(7), 553-558.
2001McLeodMcLeod R.S. (2001) "Evidence-Based Surgery." In: Norton J.A. et al. (eds) Surgery. Springer, Berlin, Heidelberg
2001/2008Guyatt et al.ChestGuyatt, G., et al. (2001) “Grades of recommendation for antithrombotic agents”. Chest, 119(1 Suppl), 3S-7S
2002Ball & PhillipsEBonCallBall, C.M. & Phillips, R. (2002). “Levels of Evidence - March 2002”, Evidence Based On Call. Retrieved from http://www.eboncall.org/content/levels.html; No longer available online. Superseded by Howick et al. 2009.
2002Bandelow et al.WFSBPBandelow, B. et al. (2002) “WFSBP Guidelines for the Pharmacological Treatment of Anxiety, obsessive-compulsive and posttraumatic stress disorders.” World J Biol Psychiatry, 3: pp.-171-199
2002Furlan et al.SpineFurlan, A. D., Brosseau, L., Imamura, M., & Irvin, E. (2002) "Massage for low-back pain: a systematic review within the framework of the Cochrane Collaboration Back Review Group." Spine, 27(17), 1896-1910.
2002Guyatt et al.UGMLGuyatt, G.H. et al. (2002) Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice: American Medical Association Press ~~ Uses the Guyatt et al. 2000 hierarchy but with different interpretation and discussion
2002Higginson et al.J Pain & Sympt Man.Higginson, I. J., Finlay, I., Goodwin, D. M., Cook, A. M., Hood, K., Edwards, A. G., ... & Norman, C. E. (2002) "Do hospital-based palliative teams improve care for patients or families at the end of life?" Journal of pain and symptom management, 23(2), 96-106.
2002Weaver et al.J Epid & Comm HealWeaver, N., Williams, J. L., Weightman, A. L., Kitcher, H. N., Temple, J. M. F., Jones, P., & Palmer, S. (2002) "Taking STOX: developing a cross disciplinary methodology for systematic reviews of research on the built environment and the health of the public." Journal of Epidemiology & Community Health, 56(1), 48-55.
2003DaviesDental UpdateDavies, R. M. (2003). "The prevention of dental caries and periodontal disease from the cradle to the grave: what is the best available evidence?" Dental update, 30(4), 170-179.
2003Devereaux & YusufJ Int MedDevereaux, PJ & Yusuf, S. (2003) “The evolution of the randomized controlled trial and its role in evidence‐based decision making”. Journal of internal medicine, 254(2), 105-113.
2003EvansJ Clin NursEvans, D. (2003) “Hierarchy of evidence: a framework for ranking evidence evaluating healthcare interventions”. J Clin Nurs, 12(1), 77-84
2003Hess et al.Respiratory CareHess, D.R. et al. (2003). "AARC Evidence-Based Clinical Practice Guideline: Care of the ventilator circuit and its relation to ventilator-associated pneumonia." Respir Care, 48(9), 869-879.
2003ICSIICSIInstitute for Clinical Systems Improvement. (2003) Evidence Grading System. available at: http://www.icsi.org ~~ No longer available online. ICSI adopted GRADE in 2011."
2003LeysHealth PolicyLeys, M. (2003) "Health care policy: qualitative evidence and health technology assessment." Health Policy, 65(3), 217-226.
2003MaddenProc. Nutrition SocietyMadden, A. M. (2003). "Changing perspectives in the nutritional management of disease." Proceedings of the Nutrition Society, 62(4), 765-772.
2003Mason & EcclesGREGMason, J. & Eccles, M.,. (2003) Guideline Recommendation and Evidence Grading (GREG). Newcastle, UK: University of Newcastle Centre for Health Services Research
2003Petticrew & RobertsJ Epi & Comm HealPetticrew, M., & Roberts, H. (2003). "Evidence, hierarchies, and typologies: horses for courses." Journal of Epidemiology & Community Health, 57(7), 527-529.
2003Tranfield, Denyer & SmartBJ ManagementTranfield, D., Denyer, D., & Smart, P. (2003) "Towards a methodology for developing evidence‐informed management knowledge by means of systematic review." British journal of management, 14(3), 207-222.
2004AnonymousThoraxAnonymous (2004) ‘Hierarchy of Evidence and Grading of Recommendations’, in Thorax, 59: 13-4
2004Ebell et al.SORTEbell, M. H., et al. (2004) “Strength of recommendation taxonomy (SORT): a patient-centered approach to grading evidence in the medical literature”. Am Fam Physician, 69(3), 548-556
2004Edlund et al.AANEdlund, W. et al. (2004) Clinical Practice Guideline Process Manual, Appendix 9. American Academy of Neurology: available at: www.aan.com"
2004GRADE Working GroupGRADEGRADE Working Group. (2004) “Grading quality of evidence and strength of recommendations”. British Medical Journal, 328, 1490
2004HessRespiratory CareHess, D. R. (2004). "What is evidence-based medicine and why should I care?" Respiratory care, 49(7), 730-741.
2004LangMcGill J MedLang, E. (2004) “The Why and How of Evidence-Based Medicine”. McGill Journal of Medicine, 8, 90-94
2004MontoriTreatments in EndocrinologyMontori, V. M. (2004). "Evidence-based endocrinology." Treatments in endocrinology, 3(1), 1-10.
2004NICENICENational Institute for Health and Clinical Excellence (NICE). (2004) NICE: Guideline Development Methods (Vol. Vol.7: Reviewing and Grading the Evidence) ~~ No longer easily accessible online.
2004ReidCleft palate-craniofacial JReid, J. (2004) "A review of feeding interventions for infants with cleft palate." Cleft palate-craniofacial journal, 41(3), 268-278.
2004Vardy & TannockAnnals of OncologyVardy, J., & Tannock, I. F. (2004). "Quality of cancer care." Annals of oncology, 15(7), 1001-1006.
2004Wagoner et al.SUNYWagoner, B. et al. (2004) “Guide to Research Methods: The Evidence Pyramid”. SUNY Downstate Medical Center EBM Tutorial. ~~ Image no longer available online.
2005AkobengArch. dis in childhoodAkobeng, A. K. (2005). "Understanding randomised controlled trials." Archives of disease in childhood, 90(8), 840-844.
2005Anderson & MatzenAndersen I, & Matzen P. (2005) Evidensbaseret Medicin [Evidence-based medicine]. Gads Forlag. ~~ German language publication, unverified, cited by Kristensen et al. 2011.
2005Cooper et al.JHSRPCooper, N., Coyle, D., Abrams, K., Mugford, M., & Sutton, A. (2005) "Use of evidence in decision models: an appraisal of health technology assessments in the UK since 1997." Journal of health services research & policy, 10(4), 245-250.
2005Harding et al.STIHarding, R., Karus, D., Easterbrook, P., Raveis, V. H., Higginson, I. J., & Marconi, K. (2005). "Does palliative care improve outcomes for patients with HIV/AIDS? A systematic review of the evidence." Sexually Transmitted Infections, 81(1), 5-14.
2005HaynesACP J ClubHaynes, R Brian. (2005) “Of studies, syntheses, synopses, summaries, and systems: the 5S evolution of information services for evidence-based health care decisions”. ACP J Club, 145(3), A8-A8
2005Melnyk & Fineout-OverholtMelnyk, B.M. & Fineout-Overholt, E.,. (2005) Evidence-Based Practice in Nursing and Healthcare: A Guide to Best Practice. Philadelphia: Lippincoot, Williams & Wilkins
2005Spindler et al.JAAOSSpindler, K. P., Kuhn, J. E., Dunn, W., Matthews, C. E., Harrell Jr, F. E., & Dittus, R. S. (2005). "Reading and Reviewing the Orthopaedic Literature: A Systematic, Evidence‐based Medicine Approach." Journal of the American Academy of Orthopaedic Surgeons, 13(4), 220-229.
2005Weightman et al.NICEWeightman, Alison, et al. (2005) Grading evidence and recommendations for public health interventions: developing and piloting a framework: Health Development Agency London, UK
2005Williams et al.Physio. Res. Int.Williams, M. T., Hardy, F., Tucker, B., Smith, M., & Maxwell, L. (2005). "Cardiothoracic physiotherapy: levels of evidence underpinning entry‐level curricula." Physiotherapy Research International, 10(2), 72-80.
2005Zhang et al.Ann. Rheum. Dis.Zhang, W., Doherty, M., Arden, N., Bannwarth, B., Bijlsma, J., Gunther, K. P., ... & Leeb, B. (2005) "EULAR evidence based recommendations for the management of hip osteoarthritis: report of a task force of the EULAR Standing Committee for International Clinical Studies Including Therapeutics (ESCISIT)." Annals of the rheumatic diseases, 64(5), 669-681.
2006BanwellDermatologyBanwell, H. (2006). "What is the evidence for tissue regeneration impairment when using a formulation of PVP-I antiseptic on open wounds?" Dermatology, 212(Suppl. 1), 66-76.
2006Bhandari & GiannoudisInjuryBhandari, M. & Giannoudis, P. V. (2006) “Evidence-based medicine: what it is and what it is not”. Injury, 37(4), 302-306
2006Busse & HeetveldInjuryBusse, J. W., & Heetveld, M. J. (2006) "Critical appraisal of the orthopaedic literature: Therapeutic and economic analysis." Injury, 37(4), 312-320.
2006ClarkeSAGEClarke A. (2006) "Evidence-based evaluation in different professional domains: similarities, differences and challenges." In: Shaw IF, Greene JC and Mark MM (eds) The Sage handbook of evaluation. London: Sage
2006Dagenais et al.J Chinese Integrative MedDagenais, S., Tricco, A. C., Bian, Z. X., Huang, W. H., & Moher, D. (2006) "Critical appraisal of clinical studies in Chinese herbal medicine." Zhong xi yi jie he xue bao, Journal of Chinese integrative medicine, 4(5), 455-466.
2006Fuster et al.EuropaceFuster, Valentin, et al. (2006) “ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: full text A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation) Developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society”. Europace, 8(9), 651-745
2006Guyatt et al.ChestGuyatt, G.H. et al. (2006) “Grading Strength of Recommendations and Quality of Evidence in Clinical Guidelines”. Chest, 129, 174-178
2006Haynes et al.Haynes, R.B., Sackett, D.L., Guyatt, G.H. & Tugwell, P. (2006) Clinical Epidemiology: how to do clinical practice research, 3rd edition, Lippincott, Williams & Wilkins: Philadelphia
2006NICENICENational Institute for Health and Clinical Excellence (NICE). (2006) Hypertension: Management of Hypertension in Adults in Primary Care, NICE Clinical Guideline 34
2006Petrisor, Keating & SchmetishInjuryPetrisor, B. A., Keating, J. & Schemitsch, E. (2006) “Grading the evidence: levels of evidence and grades of recommendation”. Injury, 37(4), 321-327
2006Schunemann, Fretheim & OxmanWHOSchunemann, H. J., Fretheim, A. & Oxman, A. D. (2006) “Improving the use of research evidence in guideline development: 9. Grading evidence and recommendations”. Health Res Policy Syst, 4, 21
2006Schunemann et al.ATSSchunemann, H. J., et al. (2006) “An official ATS statement: grading the quality of evidence and strength of recommendations in ATS guidelines and recommendations”. Am J Respir Crit Care Med, 174(5), 605-614
2006Tucker & RothAddictionTucker, J. A., & Roth, D. L. (2006) "Extending the evidence hierarchy to enhance evidence‐based practice for substance use disorders." Addiction, 101(7), 918-932.
2006Zlowodski, Jonsson & BhandariMed Prin & PracZlowodzki, M., Jönsson, A., & Bhandari, M. (2006). "Common pitfalls in the conduct of clinical research." Medical Principles and Practice, 15(1), 1-8.
2007ACOEMACOEMAmerican College of Occupational and Enviromental Medicine (ACOEM) (2007) Low back disorders. Occupational medicine practice guidelines: evaluation and management of common health problems and functional recovery in workers. 2nd ed. Elk Grove Village (IL): American College of Occupational and Environmental Medicine (ACOEM); 2007.
2007Broom & ToveyJCEBroom, A., & Tovey, P. (2007). "Therapeutic pluralism? Evidence, power and legitimacy in UK cancer services." Sociology of Health & Illness, 29(4), 551-569.
2007Daly et al.JCEDaly, J., et al. (2007) “A hierarchy of evidence for assessing qualitative health research”. J Clin Epidemiol, 60(1), 43-49
2007Lewis, Graham & StanfordScan. J RheumLewis, K. A., Graham, E. M., & Stanford, M. R. (2007). "Systematic review of ethnic variation in the phenotype of Behcet's disease." Scandinavian journal of rheumatology, 36(1), 1-6.
2007Petrisor & BhandariIndian J OrthopPetrisor, B. & Bhandari, M. (2007) “The hierarchy of evidence: Levels and grades of recommendation”. Indian J Orthop, 41(1), 11-15
2007Thachil, Mohan & BhugraJ Affective DisordersThachil, A. F., Mohan, R., & Bhugra, D. (2007) "The evidence base of complementary and alternative therapies in depression." Journal of affective disorders, 97(1), 23-35.
2007Virgilio, Chiapi & PalmarozziJ Am Ost AssVirgilio, R.F., Chiapa, A.L. & Palmarozzi, E.A. (2007) ‘Evidence-Based Medicine, Part 1. An introduction to Creating an Answerable Question and Searching the Evidence’, in Journal of the American Osteopathy Association, 107:295-7
2008Guyatt et al.UGMLGuyatt, G.H. et al. (2008) ‘How to use a patient management recommendation’ in UGML, pp.595-618
2008Guyatt et al.ChestGuyatt, G. H., et al. (2008) “Grades of recommendation for antithrombotic agents: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)”. Chest, 133(6 Suppl), 123S-131S
2008Ho, Peterson & MasoudiCirculationHo, P. M., Peterson, P. N. & Masoudi, F. A. (2008) “Evaluating the evidence: is there a rigid hierarchy?”. Circulation, 118(16), 1675-1684
2008Manchikanti et al.Pain PhysicianManchikanti, L., Singh, V., Derby, R., Helm, S., Trescot, A. M., Staats, P. S., ... & Hirsch, J. A. (2008). "Review of occupational medicine practice guidelines for interventional pain management and potential implications." Pain Physician, 11(3), 271-289.
2008SIGN 50SIGNScottish Intercollegiate Guidelines Network (SIGN). (2008) SIGN 50: A Guideline Developer's Handbook. available at: www.sign.ac.uk"
2008Sprague, McKay & ThomaClinics in Plastic SurgerySprague, S., McKay, P., & Thoma, A. (2008) "Study design and hierarchy of evidence for surgical decision making." Clinics in plastic surgery, 35(2), 195-205.
2008Sullivan & CambronNUHSSullivan, B.M. & Cambron, J.A. (2008) ‘Overview of Study Designs in Clinical Research’ [Presentation] ([email protected] CH5 Study Design)
2008Tang & BeagleholeJ Epid Comm HealthTang, KC, Choi, BCK & Beaglehole, R. (2008) “Grading of evidence of the effectiveness of health promotion interventions”. J Epidemiol Community Health, 62(9), 832-834
2008US Preventive Services Task ForceUSPSTFU.S. Preventive Services Task Force. (2008) U.S. Preventive Services Procedure Manual. AHRQ Publication No. 08-05118-EF
2009Armola et al.Am J Crit CareArmola, R. R., Bourgault, A. M., Halm, M. A., Board, R. M., Bucher, L., Harrington, L., ... & Medina, J. (2009) "Upgrading the American association of critical-care nurses’ evidence-leveling hierarchy." American Journal of Critical Care, 18(5), 405-409.
2009BigbyBigby, M. (2009) “The Hierarchy of Evidence”, in Williams, H., Bigby, M., Diepgen, T., Herxheimer, A., Naldi, L., & Rzany, B. (Eds.). (2009). Evidence-based dermatology. John Wiley & Sons.
2009Centre for Reviews and DisseminationCRDCentre for Reviews and Dissemination, University of York (2009) Systematic Reviews: CRD’s guidance for undertaking reviews in health care, 3rd edition, CRD: York.
2009Croswell & KramerJ HepatologyCroswell, J.M., & Kramer, B.S. (2009) "Clinical trial design and evidence-based outcomes in the study of liver diseases." Journal of hepatology, 50(4), 817-826.
2009DiCenso, Bayley & HaynesAnn Int MedDiCenso, A., Bayley, L. & Haynes, R. B. (2009) “ACP Journal Club. Editorial: Accessing preappraised evidence: fine-tuning the 5S model into a 6S model”. Ann Intern Med, 151(6), JC3-2, JC3-3
2009Grunze et al.WFSBPGrunze H, Vieta E, Goodwin GM, Bowden C, Licht R W et al. (2009) “The World Federation of Societies of Biological Psychiatry (WFSBP) Guidelines for the Biological Treatment of Bipolar Disorders: Update 2009 on the Treatment of Acute Mania.” The World Journal of Biological Psychiatry, 10: pp.85-116
2009Hoppe et al.JBJSHoppe, D. J., Schemitsch, E. H., Morshed, S., Tornetta III, P., & Bhandari, M. (2009) "Hierarchy of evidence: where observational studies fit in and why we need them." JBJS, 91(Supplement_3), 2-9.
2009Howick et al.CEBMHowick, J. et al. (2009) “CEBM Levels of Evidence”. Centre for Evidence-Based Medicine, www.cebm.org"
2009Manchikanti et al.Pain PhysicianManchikanti, L., Datta, S., Smith, H. S., & Hirsch, J. A. (2009) "Evidence-based medicine, systematic reviews, and guidelines in interventional pain management: part 6. Systematic reviews and meta-analyses of observational studies." Pain physician, 12(5), 819.
2010Marchevsky & WickAm J Clin PatholMarchevsky, A. M. & Wick, M. R. (2010) “Evidence levels for publications in pathology and laboratory medicine”. Am J Clin Pathol, 133(3), 366-367
2009Merlin, Weston & TooherBMCMerlin, T., Weston, A. & Tooher, R. (2009) “Extending an evidence hierarchy to include topics other than treatment: revising the Australian 'levels of evidence'”. BMC Med Res Methodol, 9, 34
2010BoothHealth Info & Lib JBooth, A. (2010) "On hierarchies, malarkeys and anarchies of evidence." Health Information & Libraries Journal, 27(1), 84-88.
2010Niederman & RichardsJ Am Coll DentNiederman, R. & Richards, D. (2010) “The challenge, access, risks, and deficits of evidence-based dentistry”. J Am Coll Dent, 77(4), 20-24
2010Sayre et al.AHASayre M R, O’Connor R E, Atkins D L, Billi J E, Callaway C W, Shuster M et al (2010) “Part 2: Evidence Evaluation and Management of Potential or Perceived Conflicts of Interest. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.” Circulation,122(Suppl 3): pp.S657-S664
2010Swanson, Schmicz & ChungPlast Reconstr SurgSwanson, J.A., Schmicz, D. & Chung, K.C.,. (2010) “How to practice evidence based medicine”. Plast Reconstr Surg, 126, 286
2010TidyTidy, C. (2010) “Different Levels of Evidence” Retrieved 06, 2012, from htttp://www.patient.co.uk/doctor/Different-Levels-of-Evidence-%28Critical-Reading%29.htm ~~ Tidy offers a number of different hierarchies here, some old, some novel.
2011Balshem et al.GRADEBalshem, H., et al. (2011) “GRADE guidelines: 3. Rating the quality of evidence”. J Clin Epidemiol, 64(4), 401-406
2011Biondi-Zoccai, Landoni & ModenaHSRBiondi-Zoccai, G., Lotrionte, M., Biondi-Zoccai, G., Landoni, G., & Modena, M. G. (2011) "A journey into clinical evidence: from case reports to mixed treatment comparisons." HSR proceedings in intensive care & cardiovascular anesthesia, 3(2), 93.
2011Biondi-Zoccai et al.HSRBiondi-Zoccai, G., Lotrionte, M., Landoni, G., & Modena, M. G. (2011). "The rough guide to systematic reviews and meta-analyses." HSR proceedings in intensive care & cardiovascular anesthesia, 3(3), 161.
2011EavesAesthet Surg JEaves, F. F., 3rd. (2011) “Got evidence? Stem cells, bias, and the level of evidence ladder: commentary on: ASAPS/ASPS position statement on stem cells and fat grafting”. Aesthet Surg J, 31(6), 718-722
2011Glover et al.EBM Page GeneratorGlover, J. et al. (2011) “EBM Page Generator”. Formerly available at http://www.ebmpyramid.org ~~ One of the most replicated images of evidence hierarchies - this is the earliest source I have been able to locate. Can be viewed elsewhere, e.g. here.
2011Gronsett Woodroffe & GetchiusAANGronseth, G.S., Woodroffe, L.M & Getchius, T.S. (2011) Clinical Practice Guideline Process Manual. AAN: available at: http://tools.aan.com/globals/axon/assets/9023.pdf.
2011Guyatt et al.GRADEGuyatt, G.H. et al. (2011) “GRADE Guidelines: 1. Introduction--GRADE evidence profiles and summary of findings tables”. Journal of Clinical Epidemiology, 64, 383-394
2011Howick et al.CEBMHowick, J., et al. (2011) “The Oxford 2011 Levels of Evidence”. Oxford Centre for Evidence-Based Medicine, available at www.cebm.net"
2011Khan et al.CRCKhan, Khalid. (2011) Systematic reviews to support evidence based medicine: How to review and apply findings of healthcare research: CRC Press, p.19
2011Kristensen et al.CRCKristensen, H. K., Persson, D., Nygren, C., Boll, M., & Matzen, P. (2011) "Evaluation of evidence within occupational therapy in stroke rehabilitation." Scandinavian journal of occupational therapy, 18(1), 11-25.
2011Mitchell & FrieseONSMitchell, S.A. & Friese, C.R. (2011) “Decision Rules for Summative Evaluation of a Body of Evidence”, ONS: Oncology Nursing Society, available at: https://www.ons.org/explore-resources/pep/decision-rules-summative-evaluation-body-evidence
2011NICENICENational Institute for Health and Clinical Excellence (NICE). (2011) CG117: Tuberculosis: clinical diagnosis and management of tuberculosis, and measures for its prevention and control. London: RCP
2011Tomlin & BorgettoAm J Occup. TherapyTomlin, G. & Borgetto, B. (2011) “Research Pyramid: A New Evidence-Based Practice Model for Occupational Therapy.” American Journal of Occupational Therapy, 65, pp.189-196.
2011TurnerEBVMATurner, S. (2011) ‘Hierarchy of Evidence’ in EBVMA, formerly available at: ebvma.org/home/content/part-1-hierarchy-evidence ~~ no longer available online.
2011Wright, Swiontkowski & HeckmanOrth Trauma DirectionsWright, J., Swiontkowski, M., & Heckman, J. (2011) "Introducing levels of evidence to the journal." Orthopedic Trauma Directions, 9(04), 27-28.
2012Baral et al.HASTEBaral, Stefan D, et al. (2012) “The highest attainable standard of evidence (HASTE) for HIV/AIDS interventions: toward a public health approach to defining evidence”. Public Health Reports, 127(6), 572
2012GethinActa Medica CroaticaGethin, G. (2012) "Understanding Data; An introduction to critical appraisal." Acta medica Croatica, 66, 147-151.
2012HaighGroup AnalysisHaigh, R. (2012) ‘Being Economical with the Evidence’, in Group Analysis, 45: 70-83
2013Elangovan et al.J PeriodontologyElangovan, S., Avila-Ortiz, G., Johnson, G. K., Karimbux, N., & Allareddy, V. (2013) "Quality assessment of systematic reviews on periodontal regeneration in humans." Journal of periodontology, 84(2), 176-185.
2013Goldet & HowickJEBMGoldet, Gabrielle & Howick, Jeremy. (2013) “Understanding GRADE: an introduction”. Journal of Evidence‐Based Medicine, 6(1), 50-54
2013Gugiu et al.Eval & the heal profsGugiu, P. C., Westine, C. D., Coryn, C. L., & Hobson, K. A. (2013) "An application of a new evidence grading system to research on the chronic care model." Evaluation & the health professions, 36(1), 3-43.
2013Joanna Briggs InstituteJBIJoanna Briggs Institute Levels of Evidence and Grades of Recommendation Working Group (October 2013) JBI Levels of Evidence, available at Joanna Briggs Institute: https://joannabriggs.org/sites/default/files/2019-05/JBI-Levels-of-evidence_2014_0.pdf
2013La RochelleEBMLa Rochelle, P. (2013) "Basic learning concepts in EBM: the bidimentional hierarchy of evidence." Evidence-based medicine, ebmed-2013.
2013Wells et al.BMCWells, C., Kolt, G. S., Marshall, P., Hill, B., & Bialocerkowski, A. (2013). "Effectiveness of Pilates exercise in treating people with chronic low back pain: a systematic review of systematic reviews." BMC medical research methodology, 13(1), 7.
2014Canadian Task ForceCTFPHECanadian Task Force on the Periodic Health Examination. (2014) Procedure Manual. http://canadiantaskforce.ca/methods/ ~~ endorses GRADE but also offers an additional novel hierarchy."
2014HansenScan. J Social MedHansen, H.F. (2014) "Organisation of evidence-based knowledge production: Evidence hierarchies and evidence typologies." Scandinavian Journal of Social Medicine, 42(13_suppl), 11-17.
2014Spruce et al.AORNSpruce, L. et al. (2014) "Introducing AORN's new model for evidence rating." AORN Journal, 99(2): 243-255
2014Steele & TiffinCTFPHESteele, R., & Tiffin, P. A. (2014) "‘Personalised evidence’for personalised healthcare: integration of a clinical librarian into mental health services–a feasibility study." Psychiatric Bulletin, 38(1), 29-35.
2015Costantino, Montano & CasazzaInt & Emerg MedCostantino, G., Montano, N., & Casazza, G. (2015) "When should we change our clinical practice based on the results of a clinical study? The hierarchy of evidence." Internal and emergency medicine, 10(6), 745-747.
2015Feldman et al.Ann. Rev. Pharma & ToxFeldman, R. D., Hussain, Y., Kuyper, L. M., McAlister, F. A., Padwal, R. S., & Tobe, S. W. (2015) "Intraclass differences among antihypertensive drugs." Annual review of pharmacology and toxicology, 55, 333-352.
2015GugiuEval & Prog. Plan.Gugiu, P. C. (2015). "Hierarchy of evidence and appraisal of limitations (HEAL) grading system." Evaluation and program planning, 48, 149-159.
2015Habib et al.ESCHabib, G. et al. for ESC Scientific Document Group (2015) “ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)
Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)”, European Heart Journal, 36(44) pp.3075–3128
2015Pinnock et al.BMCPinnock, H., Epiphaniou, E., Pearce, G., Parke, H., Greenhalgh, T., Sheikh, A., ... & Taylor, S. J. (2015) "Implementing supported self-management for asthma: a systematic review and suggested hierarchy of evidence of implementation studies." BMC medicine, 13(1), 127.
2015Puligandla et al.J Ped SurgeryPuligandla, P. S., Grabowski, J., Austin, M., Hedrick, H., Renaud, E., Arnold, M., ... & Lopez, M. E. (2015) "Management of congenital diaphragmatic hernia: A systematic review from the APSA outcomes and evidence based practice committee." Journal of pediatric surgery, 50(11), 1958-1970.
2015van Ballmoos, Ware & HardingJ Clin Med Resvon Ballmoos, M.C.W., Ware, J.H., & Haring, B. (2015) "Clinical research quo vadis? Trends in reporting of clinical trials and observational study designs over two decades." Journal of clinical medicine research, 7(6), 428.
2015Walach & LoefJ Clin EpidWalach, H., & Loef, M. (2015) "Using a matrix-analytical approach to synthesizing evidence solved incompatibility problem in the hierarchy of evidence." Journal of clinical epidemiology, 68(11), 1251-1260.
2016Garattini et al.Eur J Int MedGarattini, S., Jakobsen, J. C., Wetterslev, J., Bertelé, V., Banzi, R., Rath, A., ... & Eikermann, M. (2016) "Evidence-based clinical practice: Overview of threats to the validity of evidence and how to minimise them." European journal of internal medicine, 32, 13-21.
2016Handu et al.ANDHandu, D., Moloney, L., Wolfram, T., Ziegler, P., Acosta, A., & Steiber, A. (2016) "Academy of Nutrition and Dietetics Methodology for Conducting Systematic Reviews for the Evidence Analysis Library." Journal of the Academy of Nutrition and Dietetics, 116(2), 311–318.
2016Izzo et al.PhytotherapyIzzo, A. A., Hoon‐Kim, S., Radhakrishnan, R., & Williamson, E. M. (2016) "A critical approach to evaluating clinical efficacy, adverse events and drug interactions of herbal remedies." Phytotherapy Research, 30(5), 691-700.
2016Mupepele et al.Ecological ApplicationsMupepele, A. C., Walsh, J. C., Sutherland, W. J., & Dormann, C. F. (2016) "An evidence assessment tool for ecosystem services and conservation studies." Ecological Applications, 26(5), 1295-1301.
2016Murad et al.EBMMurad MH, Asi N, Alsawas M, & Alahdab F. (2016) “New evidence pyramid.” Evid Based Med. 21(4): pp.125-7.
2016Spruce, Van Wicklin & WoodAORNSpruce, L., Van Wicklin, S. A., & Wood, A. (2016) "AORN’s revised model for evidence appraisal and rating." AORN journal, 103(1), 60-72.
2016Thompson et al.J Am Assoc Nurse PracThompson, N., Mansfield, B., Stringer, M., Stewart, B., Potter, J., & Fernengel, K. (2016) "An evidence‐based resource for the management of comorbidities associated with childhood overweight and obesity." Journal of the American Association of Nurse Practitioners, 28(10), 559-570.
2017Featherstone et al.Health CommunicationFeatherstone, R. M., Leggett, C., Knisley, L., Jabbour, M., Klassen, T. P., Scott, S. D., ... & Hartling, L. (2017) "Creation of an Integrated Knowledge Translation Process to Improve Pediatric Emergency Care in Canada." Health Communication, 1-8.
2017Pennington et al.EJPHPennington, A., Dreaves, H., Scott-Samuel, A., Haigh, F., Harrison, A., Verma, A., & Pope, D. (2017) “Development of an Urban Health Impact Assessment methodology: indicating the health equity impacts of urban policies.” European Journal of Public Health, 27(suppl_2):56-61
2017Salimi et al.Ann. Plastic SurgerySalimi, N., Aleksejuniene, J., Yen, E. H., & Loo, A. Y. (2017) "Fistula in Cleft Lip and Palate Patients—A Systematic Scoping Review." Annals of plastic surgery, 78(1), 91-102.
2018Gil, Piva & IrrgangClin in Sports MedGil, A. B., Piva, S. R., & Irrgang, J. J. (2018) "Considerations for Assessment and Applicability of Studies of Intervention." Clinics in sports medicine, 37(3), 427–440.
2018PaezEBMPaez, A. (2018) “The “architect analogy” of evidence-based practice: Reconsidering the role of clinical expertise and clinician experience in evidence-based health care.” Journal of Evidence-Based Medicine 2018:1-8
2019Katz et al.HEALMKatz, D.L., Karlsen, M.C., Chung, M. et al. (2019) “Hierarchies of evidence applied to lifestyle Medicine (HEALM): introduction of a strength-of-evidence approach based on a methodological systematic review.” BMC Med Res Methodol 19, 178
2020Gray et al.Drug SafGray, C.M., Grimson, F., Layton, D. et al. (2020) “A Framework for Methodological Choice and Evidence Assessment for Studies Using External Comparators from Real-World Data.” Drug Saf 43, pp.623–633.
2020Jeffcoat & SollecitoCompend Contin Educ Dent.Jeffcoat, M., & Sollecito T. (2020) "Evidence, Junk Science, and Hope in a Time of Pandemic: On the Front Lines in Dentistry." Compend Contin Educ Dent. 41(8):420-424; PMID: 32870698.
2020Tsiklakis et al.Eur Arch Paed DentTsiklakis, K., Mitsea, A., Tsichlaki, A. et al. (2020) “A systematic review of relative indications and contra-indications for prescribing panoramic radiographs in dental paediatric patients.” Eur Arch Paediatr Dent 21, 387–406

This database was first compiled 20/12/2011 and received major updates on 29/06/16 and 08/10/20. 

The most recent update is 08/10/20, changelog below:

  • Added (from SR 2017): Canadian Task Force 1994; Bigos et al. (AHCPR) 1994; Oxman 1994; Hadorn et al. 1996; Liddle, Williamson & Irwig, 1997; Lloyd-Smith 1997; McPeek et al. 1998; Beckmann 1999; Bennett & Bennett 2000; Ellis 2000; Opie, Yusuf & Kubler, 2000; Weightman, Barker & Lancaster, 2000; Craven 2001; Eccles, Freemantle & Mason, 2001; McAlister & Sackett 2001; McLeod, 2001; Furlan et al. 2002; Higginson et al. 2002; Weaver et al. 2002; Davies 2003; Hess et al. 2003; Leys 2003; Madden 2003; Petticrew & Roberts 2003; Tranfield, Denyer & Smart 2003; Hess 2004; Montori 2004; Reid 2014; Vardy & Tannock 2004; Akobeng 2005; Anderson & Matzen 2005; Cooper et al. 2005; Harding et al. 2005; Spindler et al. 2005; Williams et al. 2005; Zhang et al. 2005; Banwell 2006; Busse & Heetveld 2006; Dagenais et al. 2006; Haynes et al. 2006; Tucker & Roth 2006; Zlowodski, Jonsson & Bhandari, 2006; ACOEM 2007; Broom & Tovey, 2007; Lewis, Graham & Stanford, 2007; Thachil, Mohan & Bhugra, 2007; Manchikanti et al. 2008; Sprague, McKay & Thoma, 2008; Armola et al. 2009; Bigby 2009; Centre for Reviews and Dissemination 2009; Croswell & Kramer 2009; Hoppe et al. 2009; Manchikanti et al. 2009; Booth 2010; Biondi-Zoccai et al. 2011; Kristensen et al. 2011; Wright, Swiontkowski & Heckman, 2011; Gethin 2012; Elangovan et al. 2013; Gugiu et al. 2013; Joanna Briggs Institute 2013; La Rochelle 2013; Wells et al. 2013; Hansen 2014; Spruce et al. 2014; Steele & Tiffin 2014; Costantino, Montano & Casazza 2015; Feldman et al. 2015; Gugiu 2015; Pinnock et al. 2015; Puligandla et al. 2015; van Ballmoos, Ware & Haring 2015; Walach & Loef 2015; Garattini et al. 2016; Izzo et al. 2016; Mupepele et al. 2016; Spruce, Van Wicklin & Wood, 2016; Thompson et al. 2016; Featherstone et al. 2017; Salimi et al. 2017
  • Added (from SR 2020): Gross et al. 1994; Goldbloom 1997; Granados et al. 1997; Meltzer et al. 1998; Chestnut et al. 1999; Wilkinson 1999; American Heart Association 2000; Ariens et al. 2000; Greer et al. 2000; Bandelow et al. 2002; Grunze et al. 2009; Sayre et al. 2010; Mitchell & Friese 2011; Tomlin & Borgetto 2011; Habib et al. 2015; Handu et al. 2016; Murad et al. 2016; Pennington et al. 2017; Gil, Piva & Irrgang 2018; Paez 2018; Katz et al. 2019; Gray et al. 2020; Jeffcoat & Sollecito 2020; Tsiklakis et al. 2020
  • Updated URLs for: Sackett 1989; Cook et al. 1992; Anonymous 1995; Gray 1997; NHMRC 1999; Briss et al. 2000; Roman, Silberzweig & Siu 2000; Guyatt et al. 2001/2008, 2002, 2006, 2008 and 2011; Lang 2004; Wagoner et al. 2004; Weightman et al. 2005; Virgilio Chiapi & Palmarozzi 2007; SIGN 50, 2008; USPSTF, 2008; DiCenso Bayley & Haynes 2009; Howick et al. 2009 and 2011; Marchevsky & Wick 2010; Tidy 2010; Eaves 2011; CTF 2014.
  • Removed dead links for Glover et al. 2011 and Turner 2011.