Factors associated with thiopurine non-adherence in patients with inflammatory bowel disease

Medication non-adherence seems to be a particular problem in younger patients with inflammatory bowel disease (IBD) and has a negative impact on disease outcome.

To assess whether non-adherence, defined using thiopurine metabolite levels, is more common in young adults attending a transition clinic than adults with IBD and whether psychological co-morbidity is a contributing factor. We also determined the usefulness of the Modified Morisky 8-item Adherence Scale (MMAS-8) to detect non-adherence.

Seventy young adults [51% (36) male] and 74 [62% (46) male] adults were included. Psychological co-morbidity was assessed using the Hospital Anxiety Depression Scale (HADS) and self-reported adherence using the MMAS-8.

Twelve percent (18/144) of the patients were non-adherent. Multivariate analysis [OR, (95% CI), P value] confirmed that being young adult [6.1 (1.7-22.5), 0.001], of lower socio-economic status [1.1 (1.0-1.1), <0.01] and reporting higher HADS-D scores [1.2 (1.0-1.4), 0.01] were associated with non-adherence. Receiver operator curve analysis of MMAS-8 scores gave an area under the curve (95% CI) of 0.85 (0.77-0.92), (P < 0.0001): using a cut-off of <6, the MMAS-8 score has a sensitivity of 94% and a specificity of 64% to predict thiopurine non-adherence. Non-adherence was associated with escalation in therapy, hospital admission and surgeries in the subsequent 6 months of follow up.

Non-adherence to thiopurines is more common in young adults with inflammatory bowel disease, and is associated with lower socio-economic status and depression. The high negative predictive value of MMAS-8 scores <6 suggests that it could be a useful screen for thiopurine non-adherence.