Objective versus subjective assessment of oral medication adherence in pediatric inflammatory bowel disease

Background: The objective was to examine the prevalence and frequency of oral medication nonadherence using a multimethod assessment approach consisting of objective, subjective, and biological data in adolescents with inflammatory bowel disease (IBD). Methods: Medication adherence was assessed via pill counts, patient/parent interview, and 6‐thioguanine nucleotide (6‐TGN)/6‐methylmercaptopurine nucleotide (6‐MMPN) metabolite bioassay in 42 adolescents with IBD. Pediatric gastroenterologists provided disease severity assessments. Results: The objective nonadherence prevalence was 64% for 6‐MP/azathioprine (AZA) and 88% for 5‐aminosalicylate (5‐ASA) medications, whereas subjective nonadherence prevalence was 10% for 6‐MP/AZA and 2% for 5‐ASA. The objective nonadherence frequency was 38% for 6‐MP/AZA and 49% for 5‐ASA medications, and subjective nonadherence frequency was 6% for 6‐MP/AZA and 3% for 5‐ASA. The bioassay data revealed that only 14% of patients had therapeutic 6‐TGN levels. Conclusions: The results indicate that objectively measured medication nonadherence prevalence is consistent with that observed in other pediatric chronic illness populations, and that objective nonadherence frequency is considerable, with 40%–50% of doses missed by patients. Subjective assessments appeared to overestimate adherence. Bioassay adherence data, while compromised by pharmacokinetic variation, might be useful as a cursory screener for nonadherence with follow‐up objective assessment. Nonadherence in 1 medication might also indicate nonadherence in other medications. Clinical implications and future research directions are provided. (Inflamm Bowel Dis 2008)