Objective Quantification of Adherence to Prophylaxis in Haemophilia Patients Aged 12 to 25years and Its Potential Association with Bleeding Episodes

Background: The treatment of choice for patients with severe haemophilia is prophylaxis with clotting factor. Effective prophylaxis requires optimal adherence. Most published studies are based on surveys and interviews with patients or their parents. However, studies based on objective measurements of adherence are few and inconclusive.

Objective: The main purpose of this study was to assess adherence to prophylaxis using an objective method in patients with haemophilia aged 12 to 25years as well as to assess its potential association with bleeding episodes. Secondary objectives included comparing objective and subjective adherence (questionnaire) and identifying factors potentially associated with treatment adherence.

Methods: A retrospective observational study was designed to collect data on treatment adherence and clinical course of patients in 2013. The study included haemophilia patients on prophylaxis with clotting factor concentrate; the age range was 12 to 25years. Objective adherence to treatment was measured through pharmacy dispensing records. Dispensing dates within 2013 were used for calculation. Adherence (%) was calculated by dividing the total number of International Units (IU) of factor dispensed by the total estimated number of IU and multiplying by 100. Subjective adherence was measured using an ad hoc questionnaire which was completed by the patient. The number of bleeding episodes (joint, muscle and others) was obtained from interviews with the patient at the consultation with the pharmacist and was subsequently confirmed with the patient's clinical history. Other parameters were also evaluated.

Results: We included 52 patients in the study. Average adherence of patients resulting from the analysing of dispensing records was 85.72 (SD=23.76%). The global average of bleeding episodes was 2.2 (SD=2.69). 32.6% (seventeen) patients presented with at least one joint bleeding episode versus 67.3% (thirty five) who showed no joint bleeding episodes. Likewise, only 10% (five) patients presented with one muscle bleeding episode. Even though a significant association between the rate of objective adherence and the number of bleeding episodes was not observed, a higher number of hemarthrosis was observed in less-adherent patients. Subjective adherence perceived by patients as reported by the questionnaire showed that 36 (83.7%) of the 43 patients who completed the questionnaire considered their adherence as good, whereas 7 (16.3%) of the 43 patients considered it as fair. A statistically significant relationship was found between objective adherence expressed as a percentage using dispensing records, and subjective adherence perceived by the patient (p=0.004). The other parameters evaluated were not associated with adherence to prophylaxis.

Conclusions: Measuring objective adherence using pharmacy dispensing records is a simple and useful tool. No significant correlation was found between the rate of objective adherence observed and the number of bleeding episodes; however, a higher number of hemarthrosis was observed in less-adherent patients.