Level I	Evidence from a systematic review of level II studies
Level II	Evidence from: a study of test accuracy with an independent, blinded comparison with a valid reference standard, among consecutive persons with a defined clinical presentation in diagnostic accuracy; or a randomised controlled trial study in intervention studies; or a prospective cohort study in prognosis studies
Level III‐1	Evidence from: a study of test accuracy with: an independent, blinded comparison with a valid reference standard, among non‐consecutive persons with a defined clinical presentation in diagnostic accuracy; or a pseudorandomised, controlled trial study in intervention studies
Level III‐2	Evidence from: a comparison with reference standard that does not meet the criteria required for level II and III‐1 evidence in diagnostic study; or a comparative study with concurrent controls (such as non‐randomised, experimental, cohort study, case–control study, interrupted time series with a control group) in intervention studies; or retrospective cohort study
Level III‐3	Evidence from: diagnostic case–control study in diagnostic studies; or a comparative study without concurrent controls, such as historical control and two or more single arm study, interrupted time series without a parallel control group
Level IV	Evidence from: study of diagnostic yield (no reference standard) or case series with either post‐test or pretest/post‐test outcomes