Adherence to Clotting Factor Treatment and Association with Bleeding and Health-Related Quality of Life in Persons with Hemophilia

Introduction: Measuring patient adherence to prophylactic treatment with clotting factor in persons with hemophilia includes both subjective and objective measurements. There are limited studies conducted in adherence research using objective measures and a few studies revealed lack of correlation between subjective and objective adherence measurement. The study objectives are 1) to develop an objective adherent measurement; and 2) to assess it's association with bleeding and health-related quality of life (HRQoL) using the data collected from the Hemophilia Utilization Group Study Part VI (HUGS VI), which was an observational, non-interventional study investigating adherence to factor replacement therapy among persons with hemophilia A or B.

Methods: HUGS VI enrolled participants from eight U.S. federally-supported hemophilia treatment centers in seven states (California, Colorado, Georgia, Indiana, Pennsylvania, Texas, and Washington) from 2015 to 2017. We enrolled eligible participants who either used standard half-life (SHL) products or used extended half-life (EHL) products for less than six weeks. We collected data on socio-demographics, bleeds, joint problems, and pain via surveys, as well as HRQoL, as measured by SF-12 at enrollment and at each three-month follow-up. We collected monthly factor prescription data from the clinical chart, and monthly factor dispensing records from the participants' pharmacy. We calculated factor treatment for the proportion of days covered (PDC) as the sum of the days of treatment available based on dispensing records, divided by the sum of the days of treatment prescribed based on prescription records for nine months post-enrollment. PDC ≥0.8 was considered an objective measure of adherence to factor treatment. The number of bleeds was summed from each of three quarterly follow-up surveys. We defined EHL users as participants who started an EHL product during the study period, either six weeks prior to enrollment or anytime during the nine months follow up. Association of PDC with nine months bleeds, ratings of chronic pain, and SF-12 scores in the nine-month follow-up were analyzed using Pearson correlation and Student T-Tests.

Results: We analyzed a sample of 69 adults (age ≥18 years) with moderate or severe hemophilia using prophylactic treatment who completed at least baseline and nine-month follow-up surveys and had both prescription and dispensing records. Mean age was 28.9±10.3 (standard deviation) years, 91.3% were hemophilia A, and 65.2% were adherent to clotting factor treatment with PDC ≥0.8. EHL users were less likely to be adherent to the treatment than non-EHL users (adherence rate was 47.4% vs. 72.0%, p=0.06). PDC was significantly and negatively correlated with nine months of joint bleeds (correlation coefficient r=-0.30, p=0.01), and total bleeds (r=-0.33, p=0.026), but positively correlated with SF-12 physical composite score (r=0.32, p=0.009). PDC was not correlated with chronic pain (r=0.08, p=0.51) or SF-12 mental composite score (r=0.03, p=0.79). The participants who were adherent to factor treatment had fewer mean joint and total bleeds (2.6±4.1 vs. 1.3±2.1, p=0.08, and 4.9±5.6 vs. 2.9±3.8, p=0.07, respectively) than those non-adherent to treatment, although the differences did not reach statistical significance. Compared to participants who were adherent to treatment, non-adherent participants had a lower SF-12 physical composite score, with an approximately 5-point difference (43.4±10.6 vs. 48.0±9.1, p=0.07).

Conclusions: As the data collection period occurred when EHL products became commercially available, treatment adherence may have led to treatment selection as participants switched from SHL to EHL products. Our data showed that participants who were non-adherent to treatment were more likely to be EHL users. Better adherence with higher PDC was moderately correlated with fewer bleeds, but higher HRQoL physical health composite score. The objective adherence measurement developed in this study should be further studied to investigate whether switching from SHL to EHL improves treatment adherence and its association with clinical outcomes.