Foundations for health status metrology: the stability of MOS SF-36 PF-10 calibrations across samples.

Interest in applying probabilistic conjoint measurement (PCM) models, such as those devised by the late Georg Rasch, to health status and quality of life data has grown significantly in the last few years. Applications have yet, however, to fully realize the opportunities for scientific generalization and practical convenience PCM offers. This article fleshes out the substance of some of these opportunities by comparing eight separate PCM calibrations of the SF-36 ten-item physical functioning scale (PF-10). The initial average correlation across the 28 pairs of calibrations is .84; after taking advantage of the PCM model's capacity to account for missing data by omitting from the comparisons items that vary due to sample idiosyncracies, the average correlation is .90. Opportunities for, and limitations on, generalization from PF-10 measures are explored.