Therapietrouw bij TNF-α-blokkers valt tegen*

Objective

To investigate adherence rates in tumor necrosis factor-α (TNF-α)-inhibitors in Crohn's disease (CD) and rheumatoid arthritis (RA) by systematic review of medical literature.

Methods

A structured search of PubMed between 2001 and 2011 was conducted to identify publications that assessed treatment with TNF-α inhibitors providing data about adherence in CD and RA. Therapeutic agents of interest where adalimumab, infliximab and etanercept, since these are most commonly used for both diseases. Studies assessing only drug survival or continuation rates were excluded. Data describing adherence with TNF-α inhibitors were extracted for each selected study. Given the large variation between definitions of measurement of adherence, the definitions as used by the authors where used in our calculations. Data were tabulated and also presented descriptively. Sample size-weighted pooled proportions of patients adherent to therapy and their 95%CI were calculated. To compare adherence between infliximab, adalimumab and etanercept, the adherence rates where graphed alongside two axes. Possible determinants of adherence were extracted from the selected studies and tabulated using the presented OR.

Results

Three studies on CD and three on RA were identified, involving a total of 8147 patients (953 CD and 7194 RA). We identified considerable variation in the definitions and methodologies of measuring adherence between studies. The calculated overall sample size-weighted pooled proportion for adherence to TNF-α inhibitors in CD was 70% (95%CI: 67%-73%) and 59% in RA (95%CI: 58%-60%). In CD the adherence rate for infliximab (72%) was higher compared to adalimumab (55%), with a relative risk of 1.61 (95%CI: 1.27-2.03), whereas in RA adherence for adalimumab (67%) was higher compared to both infliximab (48%) and etanercept (59%), with a relative risk of 1.41 (95%CI: 1.3-1.52) and 1.13 (95%CI: 1.10-1.18) respectively. In comparative studies in RA adherence to infliximab was better than etanercept and etanercept did better than adalimumab. In three studies, the most consistent factor associated with lower adherence was female gender. Results for age, immunomodulator use and prior TNF-α inhibitors use were conflicting.

Conclusion

One-third of both CD and RA patients treated with TNF-α inhibitors are non-adherent. Female gender was consistently identified as a negative determinant of adherence.

Conflict of interest and financial support: a disclosure form provided by the author is available along with the full text of this article at www.ntvg.nl, search for A7180; click on ‘Belangenverstrengeling’ (‘Conflict of interest’).