Objectives:Thiopurines, commonly used to treat inflammatory bowel disease, cause lymphopenia and red blood cell macrocytosis, requiring therapeutic monitoring. Mean corpuscular volume/white blood cell (MCV/WBC) ratio has been proposed as a surrogate for therapeutic monitoring. Our aim was to investigate MCV/WBC ratio for assessing clinical response to thiopurines among pediatric patients with inflammatory bowel disease.Methods:We performed a retrospective cross-sectional study at a tertiary care center using laboratory results and standardized physician global assessments (PGA) among pediatric patients taking thiopurines. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), fecal calprotectin, and 6-thioguanine nucleotides were assessed when available. The primary outcome was association between MCV/WBC ratio and clinical remission assessed by ESR, CRP, calprotectin, or PGA. We also used a composite outcome requiring all available data to be normal. Analyses were limited to 1 occurrence per patient, >60 days after starting thiopurine, and comparators were required to be within 14 days of one another.Results:A total of 471 patients met inclusion criteria. MCV/WBC ratio poorly predicted quiescent disease as defined by PGA (area under receiver operating characteristic curve [AuROC] 0.55, 95% confidence interval [CI] 0.43–0.66). MCV/WBC ratio better predicted quiescent disease defined as normal CRP (AuROC 0.64, 95% CI 0.58–0.70) or normal ESR (AuROC 0.59, 95% CI 0.52–0.66). When the composite outcome measure was used, MCV/WBC ratio had an AuROC of 0.65 (95% CI 0.59–0.70), indicating it is reasonably accurate in discriminating between clinical remission and active disease.Conclusions:MCV/WBC ratio is a noninferior, easy, and low-cost alternative to thiopurine metabolite monitoring.

Balancing risks of immune suppressive medications against risk of chronic disease is challenging for clinicians and families. Available aids commonly lack comparative information needed to inform treatment decisions. We developed a simple video aid to illustrate competing risks associated with medications and underlying disease in context of pediatric inflammatory bowel disease. Those who viewed the video aid had more realistic risk perceptions than those who did not view it. The video aid is adaptable for other conditions. It required only commonly accessible software and little cost, thereby making an aid of this style an attractive option for health care professionals interested in communicating comparative risk data to patients.