Test-Retest Reliability Analysis of the Patient Reported Outcomes Burdens and Experiences (PROBE)

Background: Patient Reported Outcomes Burdens and Experiences (PROBE) questionnaire was developed for assessing health status in patients with bleeding disorders, specifically, hemophilia. Phase I of PROBE study confirmed robustness of methodology and feasibility of the questionnaire.

Objective: To investigate the test-retest reliability of PROBE questionnaire

Methods: Patients and non-hemophilia individuals who attended an hemophilia related workshops were invited to participate in this study. All participants were asked to fill out a PROBE questionnaire for 3 times. The paper-based questionnaires were collected immediately after being filled out on day 1 and day 2. Participants were instructed to log into the website within 2 weeks and fill out the web-based questionnaire. Test-retest reliability was analyzed.

Results: A total of 63 participants were enrolled in this study with a median age of 50 (range 14-76) years. Of these, 30 (47.6%) were hemophilia patients or carriers, 33 (52.5%) were participants with no known bleeding disorders. On general health domain, Kappa coefficients ranged from 0.69 to 0.90, indicating substantial to almost perfect agreement for all items. Reliability of web-based questionnaire showed moderate to substantial agreement for all except 1 item. For hemophilia related domain, Kappa coefficients ranged from 0.5-1.0. Of these, 5 of 11 items were in perfect agreement (Kappa=1.0). Reliability of web-based questionnaire were in substantial to almost perfect agreement. For overall health related quality of life, EQ-5D had Kappa coefficients of 0.62 to 0.89. Intraclass correlation coefficient of visual analog scale (VAS) was 0.90 (95% confidence interval; 0.83-0.94). Test-retest reliability was comparable between hemophilia patients and participants with no known bleeding disorders.

Conclusions: The results suggest that PROBE is a reliable tool to assess patients reported outcomes for hemophiliacs. Test-retest reliability analysis showed that the agreement was comparable between two participant populations. This result suggests that PROBE tool may be used to collect and compare not only patient reported outcome in hemophilia, but to generate norm values in appropriate control population. The Web-based questionnaire has an acceptable agreement with the standard paper-based version.