Development of a Disease-Specific Ureteral Calculus Patient Reported Outcome Measurement Instrument.
INTRODUCTION: Patient reported outcome measures (PROMs) are powerful instruments to assess the impact of a disease on health from the patient's perspective. We describe the process of designing, testing, and validating the Cambridge Ureteral Stone PROM (CUSP). MATERIALS AND METHODS: Patients recently diagnosed with ureteral stones were approached for participation in focus groups, structured interviews, and test-retest validation studies. Statistical tests included Cronbach's alpha for internal consistency, Spearman's and Pearson's correlation coefficients for test-retest validity, permutation tests of equality of means and Spearman's correlation coefficients for discriminant validity. RESULTS: Forty-three patients participated in the development of the CUSP. Twenty-two patients were involved in the focus groups and structured interviews and a further 21 participated in the prospective test-retest study. Expressed comments were grouped into seven broad health domains: pain, fatigue, sleep disturbance, work and daily activities, anxiety, gastrointestinal (GI) symptoms, and urinary symptoms. Items were selected from established PROM platforms to form the draft (dCUSP) instrument, which was then used for test-retest validation and item reduction. All domains scored highly for Cronbach's alpha (>0.8), with the exception of GI symptoms. Large Spearman's (>0.76) and Pearson's correlation estimates (>0.83) were obtained for test-retest validity, suggesting that answers were reliable through the time period tested. The estimates of the Spearman's correlation coefficient between each pair of domains ranged from 0.17 to 0.78 and the upper bounds of the corresponding 95% confidence intervals were all smaller than 0.95, suggesting that each domain measures something different. The tests of equality of the mean of scores of the control (n = 25) and patient groups were all significant, suggesting that CUSP successfully discriminated patients suffering from ureteral stones for every domain. CONCLUSION: CUSP is a patient-derived ureteral stone PROM, which can be used to measure ureteral stone disease health outcomes from the patient's point of view.