Usefulness of mean corpuscular volume as a surrogate marker for monitoring thiopurine treatment in inflammatory bowel disease

Thiopurines are commonly used drugs in inflammatory bowel disease. Intracellular levels of thiopurine metabolites [i.e. 6-thioguaninenucleotides (6-TGN)] are associated with efficacy and toxicity. Because 6-TGN measurement is not globally available, the mean corpuscular volume (MCV) has been proposed as a surrogate marker for monitoring thiopurine therapy. To analyze the relationship between MCV and efficacy of thiopurines, defined as either response to therapy or 6-TGN levels. A systematic search on PubMed was performed. Fifteen studies were included. In six studies, a positive association was found between ΔMCV and 6-TGN. In four studies, it was suggested that ΔMCV can be used to predict clinical remission. In five articles, no association was found. In the majority of articles, it was reported that ΔMCV is useful in guiding intracellular metabolite levels. However, there is insufficient evidence showing that ΔMCV can predict clinical remission