Reliability and Construct Validity of the Patient-Reported Outcomes Measurement Information System (PROMIS) Instruments in Women with Fibromyalgia

Objective: The Patient-Reported Outcomes Measurement Information System (PROMIS) was developed to standardize measurement of clinically relevant patient-reported outcomes. This study evaluated the reliability and construct validity of select PROMIS static short-form (SF) instruments in women with fibromyalgia.

Design: Analysis of baseline data from the Fibromyalgia Activity Study with TENS (FAST), a randomized controlled trial of the efficacy of transcutaneous electrical nerve stimulation.

Setting: Dual site, university-based outpatient clinics.

Subjects: Women aged 20 to 67 years diagnosed with fibromyalgia.

Methods: Participants completed the Revised Fibromyalgia Impact Questionnaire (FIQR) and 10 PROMIS static SF instruments. Internal consistency was calculated using Cronbach alpha. Convergent validity was examined against the FIQR using Pearson correlation and multiple regression analysis.

Results: PROMIS static SF instruments had fair to high internal consistency (Cronbach α = 0.58 to 0.94, P < 0.05). PROMIS 'physical function' domain score was highly correlated with FIQR 'function' score (r = -0.73). The PROMIS 'total' score was highly correlated with the FIQR total score (r = -0.72). Correlations with FIQR total score of each of the three PROMIS domain scores were r = -0.65 for 'physical function,' r = -0.63 for 'global,' and r = -0.57 for 'symptom' domain. PROMIS 'physical function,' 'global,' and 'symptom' scores explained 58% of the FIQR total score variance.

Conclusions: Select PROMIS static SF instruments demonstrate convergent validity with the FIQR, a legacy measure of fibromyalgia disease severity. These results highlight the potential utility of select PROMIS static SFs for assessment and tracking of patient-reported outcomes in fibromyalgia.