Classification criteria in rheumatic diseases: a review of methodologic properties

To identify classification criteria for the rheumatic diseases and to evaluate their measurement properties and methodologic rigor using current measurement standards.

We performed a systematic review of published literature and evaluated criteria sets for stated purpose, derivation and validation sample characteristics, methods of criteria generation and reduction, and consideration of validity, and reliability.

We identified 47 classification criteria sets encompassing 13 conditions. Approximately 50% of the criteria sets were developed based on expert opinion rather than patient data. Of the 47 criteria sets, control samples were derived from patients with rheumatic disease in 15 (32%) sets, from patients with nonrheumatic diseases in 4 (9%) sets, and from healthy participants in 2 (4%) sets. Where patient data were used, the number of cases ranged from 20-588 and the number of controls from 50-787. In only 1 (2%) criteria set was there a distinct separation between investigators who derived the criteria set and clinicians who provided cases and controls. Authors commented on the need for individual criterion to be reliable in 5 (11%) sets, precise in 5 (11%) sets; authors noted the importance of content validity in 12 (26%) sets, and construct validity in 12 (26%) sets.

The variation in methodologic rigor used in sample selection affects the validity and reliability of the criteria sets in different clinical and research settings. Despite potential deficiencies in the methods used for some criteria development, the sensitivity and specificity of many criteria sets is moderate to strong.