Categorizing factors of adherence to parenteral treatment in growth hormone deficiencies and hemophilia: What should be the targets for future research?

Adherence to treatment regimens in growth hormone dysregulations and hemophilia is related to better outcome and fewer complications over time. Subcutaneous growth hormone injection and intravenous blood factor replacement therapies are parenteral treatments with a comparable regimen calling for similar behavioral processes. Although we have lists of possible factors influencing adherence in these conditions, the evidence is scattered. The objective of this study was to systematically review empirical studies linking factors of adherence with measures of adherence. To categorize the factors, we used a taxonomy from the diabetes literature. We used four major electronic databases to identify articles. We synthesized 27 articles dated 2011-2017 corresponding to inclusion criteria. Results showed a consistent proportion of 20%-25% participants with adherent issues. Strong arguments pointed to the transition to self-care in pediatrics as a vulnerability period (7/27 reports). We found the domains of individual factors (<30% reports), relational factors (<13%), health care (<30%), to be understudied in comparison with that of demographic or clinical context (>74%), and practical issues (>37%). The results suggest that future research should focus on modifiable factors of adherence, with appropriate measurement and intervention strategies. One central methodological limitation of reviewed reports was the lack of longitudinal designs, and the quasi absence of behavioral trial targeting modifiable factors of adherence. A new research agenda should be set in these rare diseases as higher adherence should translate into improved outcome and better quality of life for patients and their families.