Diagnostic performance tests for suspected scaphoid fractures differ with conventional and latent class analysis.

BACKGROUND: Evaluation of the diagnostic performance characteristics of radiographic tests for diagnosing a true fracture among suspected scaphoid fractures is hindered by the lack of a consensus reference standard. Latent class analysis is a statistical method that takes advantage of unobserved, or latent, classes in the data that can be used to determine diagnostic performance characteristics when there is no consensus reference (gold) standard. PURPOSES: We therefore compared the diagnostic performance characteristics of MRI, CT, bone scintigraphy, and physical examination to identify true fractures among suspected scaphoid fractures. PATIENTS AND METHODS: We used data from two studies, one that prospectively studied 34 patients who had MRI and CT of the wrist, and a second that studied 78 patients who had MRI, bone scintigraphy, and structured physical examination. We compared the diagnostic performance characteristics calculated by latent class analysis with those calculated using formulas based on a reference standard. RESULTS: In the first cohort, the calculated sensitivity and specificity with latent class analysis were different than those with traditional reference standard-based calculations for the CT in the scaphoid planes (sensitivity, 0.78 versus 0.67; specificity, 1.0 versus 0.96) and the MRI (sensitivity, 0.80 versus 0.67; specificity, 0.93 versus 0.89). In the second cohort, the greatest differences were in the sensitivity of MRI (0.84 versus 0.75) and the sensitivities of physical examination maneuvers (range, 0.63-0.73 versus 1.0). CONCLUSIONS: The diagnostic performance characteristics calculated using latent class analysis may differ from those calculated according to formulas based on a reference standard. We believe latent class analysis merits further study as an option for assessing diagnostic performance characteristics for orthopaedic conditions when there is no consensus reference standard. LEVEL OF EVIDENCE: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.