Erythrocyte mean corpuscular volume as a surrogate marker for 6‐thioguanine nucleotide concentration monitoring in patients with inflammatory bowel disease treated with azathioprine or 6‐mercaptopurine

• Published in: Inflammatory bowel diseases Vol. 9; no. 4; pp. 237 - 245
• Main Authors: Thomas, Carlton W., Lowry, Philip W., Franklin, Curtis L., Weaver, Amy L., Myhre, Gennett M., Mays, Dennis C., Tremaine, William J., Lipsky, James J., Sandborn, William J.
• Format: Journal Article
• Language: English
• Published: Philadelphia Lippincott Williams & Wilkins, Inc 01-07-2003
• Subjects: 6-Mercaptopurine; 6‐Thioguanine Nucleotide Concentration; Adolescent; Adult; Aged; Aged, 80 and over; Azathioprine; Azathioprine - therapeutic use; Biomarkers - analysis; Blood; Blood levels; Endpoint Determination; Erythrocyte Indices; Erythrocytes; Erythrocytes - physiology; Female; Guanine Nucleotides - analysis; Humans; Immunosuppressive Agents - therapeutic use; Inflammatory Bowel Disease; Inflammatory bowel diseases; Inflammatory Bowel Diseases - blood; Inflammatory Bowel Diseases - drug therapy; Inventories; Leukocyte Count; Leukocytes; Leukopenia; Male; Mean Corpuscular Volume; Mercaptopurine - therapeutic use; Middle Aged; Nucleotides; Remission; Severity of Illness Index; Surveys and Questionnaires; Thionucleotides - analysis; Treatment Outcome
• ISSN: 1078-0998; 1536-4844
• DOI: 10.1097/00054725-200307000-00004

Mean corpuscular volume may correlate with erythrocyte 6‐thioguanine nucleotide concentrations in patients treated with azathioprine and 6‐mercaptourine. We conducted a study of 166 patients with inflammatory bowel disease treated with azathioprine or 6‐mercaptopurine to determine the relationship between mean corpuscular volume and erythrocyte 6‐thioguanine nucleotide concentrations, disease activity as measured by the Inflammatory Bowel Disease Questionnaire (active disease <170, remission >170), and leukopenia. Blood was submitted for mean corpuscular volume, whole blood 6‐thioguanine nucleotide concentration, and leukocyte count. The mean ± SD mean corpuscular volume during treatment was 94.7 ± 6.6 fL and the mean ± SD change in mean corpuscular volume was 7.5 ± 6.3 fL. There were significant correlations between mean corpuscular volume and erythrocyte 6‐thioguanine nucleotide concentration (rs = 0.33, p < 0.001) and between change from baseline in mean corpuscular volume and erythrocyte 6‐thioguanine nucleotide concentration (rs = 0.26, p = 0.001). There was no correlation between Inflammatory Bowel Disease Questionnaire scores and mean corpuscular volume values (rs = 0.01, p = 0.94). The mean corpuscular volume values in 55 patients with active disease and 111 patients in remission were similar (95.1 vs. 94.5 fL, p = 0.57). There was a weak negative correlation between the mean corpuscular volume and the leukocyte count, (rs = −0.18, p = 0.022).
In patients with inflammatory bowel disease treated with azathioprine or 6‐mercaptopurine, mean corpuscular volume and change from baseline in mean corpuscular volume correlated with erythrocyte 6‐thioguanine nucleotide concentrations and negatively with leukocyte counts, but did not correlate with disease activity as measured by the Inflammatory Bowel Disease Questionnaire. Measurement of mean corpuscular volume is a simple and inexpensive alternative to measurement of 6‐thioguanine nucleotide concentrations in patients treated with azathioprine or 6‐mercaptopurine.