The Validity and Relative Precision of MOS Short-, and Long- Form Health Status Scales and Dartmouth COOP Charts

TLDR

The study estimated the validity and relative precision of four measurement methods—MOS long‑ and short‑form scales, global items, and COOP Poster Charts—in assessing six general health concepts and tested their ability to discriminate adult patients from those with severe chronic medical or psychiatric conditions. The authors compared the four methods across 638 adult patients and two clinical groups (168 severe chronic medical, 163 psychiatric) to evaluate discrimination precision. Long‑form scales had higher relative precision than short‑form and single‑item measures, with short‑form multi‑item scales achieving a median RP of .93 versus .81 for global items and .67 for poster charts, and these differences—driven by scale coarseness, reliability, and content—affect score interpretation, statistical power, and confidence interval width.

Abstract

This study estimated the validity and relative precision (RP) of four methods (MOS long- and short-form scales, global items, and COOP Poster Charts) in measuring six general health concepts. The authors also tested whether and how precisely each method discriminated relatively well adult patients (N = 638) from those with only severe chronic medical (N = 168) and only psychiatric conditions (N = 163), as clinically defined. For comparisons between the well group and both medical and psychiatric groups, RP estimates favored longform over short-form, multi-item scales, and favored multi-item scales over single-item global measures and poster charts. In relation to long forms, short-form multi-item scales achieved a median RP of .93; RP estimates for global items and poster charts were .81 and .67, respectively. Variations in RP across methods and concepts were linked to differences in the coarseness of measurement scales, reliability, and content (including the effects of chart illustrations). These variations in RP have implications for the interpretation of scores, the statistical power of comparisons between clinical groups, and the size of confidence intervals around individual patient scores