Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Related Content Quick Reference Download Section PDF Listen +++ ++Table Graphic Jump LocationLevels of EvidenceaView Table||Download (.pdf) Levels of Evidencea Level of Evidence Grade Definition 1 A Independent blinded comparison of sign or symptom results with a criterion standard of diagnosis among a large number of consecutive patients suspected of having the target condition 2 B Independent blinded comparison of sign or symptom with a criterion standard of diagnosis among a small number of consecutive patients suspected of having the target condition 3 C Independent blinded comparison of sign or symptom with a criterion standard of diagnosis among nonconsecutive patients suspected of having the target condition 4 C Nonindependent comparison of sign or symptom with a criterion standard of diagnosis among samples of patients who obviously have the target condition plus, perhaps, normal individuals 5 C Nonindependent comparison of sign or symptom with a standard of uncertain validity aModified from Holleman and Simel.13