ITEM 23.  Report estimates of variability of diagnostic accuracy between subgroups of participants, readers or centers, if done.


Example

For detection of hemodynamically significant main renal artery stenosis, sensitivity and specificity were 90% (...) for magnetic resonance angiography (...) When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. [1]

Since variability is the rule rather than the exception, researchers should explore possible sources of heterogeneity in results, within the limits of the available sample size. The best practice is to plan subgroup analyses before the start of the study.[2] In the example above, the authors report separate estimates for patients with fibromuscular dysplasia. They did not specify whether they planned this subgroup analysis prior to the data collection.

References
1.

Leung DA, Hoffmann U, Pfammatter T, et al. Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease. Hypertension 1999; 33:726-31.
2. Oxman AD, Guyatt GH. A consumer's guide to subgroup analyses. Ann Intern Med 1992; 116:78-84.