Optimising Blood Test Monitoring Frequency for Inflammatory Bowel Disease Patients: Balancing Adherence, Comfort and...

Inflammatory bowel disease (IBD) therapies can cause myelosuppression and hepatitis. The European Crohn's and Colitis Organisation (ECCO) recommends 3-monthly blood test monitoring; however, these recommendations are largely based on expert consensus, and real-world evidence informing optimal long-term monitoring intervals remains limited.

To determine the incidence of medication-related hepatitis and myelosuppression in a population-based IBD cohort and estimate the laboratory monitoring burden required to detect clinically significant adverse events.

A retrospective cohort study was performed using the Manawatū IBD incidence cohort. Patients diagnosed with IBD between 1 January 2011 and 31 December 2015 were followed longitudinally until 31 December 2022. Medication exposure, laboratory results, and clinical outcomes were recorded. Hepatitis was defined as alanine aminotransferase (ALT) > 2 × the upper limit of normal, while myelosuppression was defined as a neutrophil count < 1.0 × 10⁹/L. Patients were followed from diagnosis until the first outcome event or last recorded follow-up. Medication exposure was analysed as a time-varying variable using cox proportional hazards regression, and the duration of laboratory monitoring required to detect one adverse event was calculated.

Among 204 incident cases, 12 were excluded due to prediagnosis hepatitis or myelosuppression, leaving 192 patients for analysis. Twenty-four hepatitis events and two myelosuppression events were observed during 1739 patient-years of follow-up. 6-mercaptopurine (hazard ratio [HR] 39.2, p < 0.001), azathioprine (HR 6.26, p = 0.002), methotrexate (HR 9.94, p = 0.004) and lower mean corpuscular volume (HR 0.89, p = 0.001) were independently associated with hepatitis. Following the initial 6 months of therapy, one hepatitis event was detected for every 33 patient-years of stable thiopurine exposure monitored with routine quarterly blood testing.

Clinically significant hepatitis and myelosuppression were uncommon in this population-based IBD cohort, particularly after the initial 6 months of therapy. These findings suggest that reduced laboratory monitoring frequency in carefully selected patients with established treatment stability warrants evaluation.