Table 1.

Threats to validity of diagnostic accuracy studies

Common threats to validity	Definition
Internal validity (bias)
Context bias	Experimental test more likely to be reported as abnormal in populations with high disease prevalence
Clinical review bias	Experimental test or reference standard interpreted with knowledge of participant clinical characteristics
Test review bias	Experimental test interpreted with knowledge of the reference standard test results
Diagnostic review bias	Reference standard test interpreted with knowledge of the experimental test results
External validity (generalizability)
Spectrum bias	Disease severity, participant demographics or participant co-morbidity influence experimental test accuracy
Limited challenge bias	Potential study participants with confounders known to influence experimental test accuracy excluded from study