PRM191 - LONGITUDINAL CONSTRUCT VALIDITY OF THE HEMOPHILIA CAREGIVER IMPACT MEASURE

Abstract

The Hemophilia Caregiver Impact (HCI) measure is a 36-item self-reported measure with seven subscales that tap negative aspects and one subscale tapping the positive aspects of caregiving for people with hemophilia. The measure has exhibited reliability and validity in a large cross-sectional study but its longitudinal construct validity is unknown. This study’s objective was to evaluate the responsiveness of the HCI to clinically important change, and to provide interpretation guidelines. This web-based study invited follow-up data from 458 hemophilia caregivers involved in the HCI’s validation study. Measures included the HCI; a Likert item querying Global Assessment of Change (GAC) in Caregiver-Burden; and demographic characteristics. Responsiveness was estimated using the Modified Standardized Response Mean (MSRM), and was computed separately for people who reporting better or worse burden as compared to ‘same’ groups. The minimally important difference (MID) was computed for those who reported lesser or more caregiver burden. Linear regression models evaluated the relationship between HCI subscale scores and Burden Summary at follow-up and transition groups (better, same, worse). The study sample included 323 caregivers (71% response rate), with mean follow-up of 21.9 months (range 17.6-27.2). The HCI Burden Summary score and all negative-burden subscales but not the positive emotions subscale evidenced responsiveness to clinically important differences, showing statistically significant differences by transition group. The MIDs were relatively small (+1.7-3.2 points), and the MSRM were small effect sizes. For example, the Burden Summary MID was -2.2 to 2.6, for improved vs. worsened burden. The Burden Summary score was equally sensitive to improved vs. worsened burden (MSRM of -0.32 and 0.35, respectively). The HCI demonstrated longitudinal construct validity, and was sensitive to subgroup changes reflecting self-reported changes in caregiver burden. The HCI thus shows promise for use in clinical hemophilia studies as a caregiver-based tool for evaluating treatments.