Establishing “Normal” Patient-Reported Outcomes Measurement Information System Physical Function and Pain Interference Scores: A True Reference Score According to Adults Free of Joint Pain and Disability

Numerous recent studies have demonstrated the validity and efficiency of the National Institutes of Health Patient-Reported Outcomes Measurement Information System (PROMIS) forms in patients undergoing orthopaedic surgical procedures. It is assumed that a score of 50 in each domain represents the health state of a “reference” population, but this threshold has not been definitively proven. In order to truly assess whether a given orthopaedic intervention is successful, the comparative scores of healthy individuals must be known for any given health domain measured. Therefore, the purpose of this study was to determine baseline scores for the PROMIS general physical function (PROMIS-PF), pain interference (PROMIS-PI), and upper-extremity physical function (PROMIS-UE) domains in physically healthy, asymptomatic adult individuals. We hypothesized that, in individuals <40 years old, the mean PROMIS-PF and PROMIS-UE scores would be >50 and PROMIS-PI scores would be <50. We further hypothesized that these scores would be impacted by participant age. METHODS: Three PROMIS computer adaptive test (CAT) domains were administered (either in person or through email) to healthy adult volunteers. These domains included PROMIS-PF, PROMIS-UE, and PROMIS-PI. Individuals who reported joint pain or dysfunction were excluded. RESULTS: In total, 294 healthy volunteers with a mean age of 33.2 years (range, 18 to 83 years) completed all 3 PROMIS CAT forms. The mean (and standard deviation) PROMIS-UE, PROMIS-PF, and PROMIS-PI scores were 55.9 ± 6.6, 59.7 ± 8.0, and 43.6 ± 7.6, respectively, for individuals <40 years old and 51.2 ± 8.2, 52.9 ± 7.6, and 49.0 ± 8.0, respectively, for individuals ≥40 years old. Age correlated significantly with PROMIS-UE and PROMIS-PF in the older cohort. CONCLUSIONS: For individuals <40 years old, baseline PROMIS-PF scores were significantly higher than 50 and PROMIS-PI scores were significantly lower. This difference was less pronounced in individuals ≥40 years old. When treating young patients, clinicians should be cognizant of these healthy baseline scores. CLINICAL RELEVANCE: In this study, reference range for asymptomatic musculoskeletal volunteers was determined across PROMIS CAT forms. These reference scores are important in treating and counseling patients with musculoskeletal conditions in order to determine relative impairment or functional capabilities.