Achieving reliable pain change scores forindividuals in the postoperative phase: carefullychoose sampling density, test length, andadministration mode


Despite tremendous efforts to increase the reliability of pain measures and other self-report instruments, improving or evenevaluating the reliability of change scores has been largely neglected. In this study, we investigate the ability of 2 instruments from thePatient-Reported Outcomes Measurement Information System, pain interference (6 items) and pain behavior (7 items), to reliablydetect individual changes in pain during the postsurgical period of a hernia repair in 98 patients who answered daily diaries overalmost 3 weeks after surgery. To identify the most efficient strategy for obtaining sufficiently reliable estimates of change (reliability.0.9), the number of measurement occasions over the study period (sampling density), the number of items (test length), and themode of administration (ie, static short form vs Computer adaptive testing) were manipulated in post-hoc simulations. Reliabilities fordifferent strategies were estimated by comparing the observed change with the best approximation of “real” (ie, latent) change. Wefound (1) that near perfect reliability can be achieved if measures from all days over the whole study period, obtained with all paininterference or pain behavior items, were used to estimate the observed change, (2) that various combinations of the number ofitems and the number of measurement occasions could achieve acceptable reliability, and (3) that computer adaptive testings weresuperior to short forms in achieving sufficient reliability. We conclude that the specific strategy for assessing individual postoperativechange in pain experience must be selected carefully.

Alexander Obbarius
Alexander Obbarius
Psychometrics and Health Outcomes