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Thiopurine S-methyltransferase levels may predict azathioprine toxicity in Behçet’s disease
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Low levels of thiopurine S-methyltransferase may be predictive of adverse events caused by azathioprine toxicity in patients with Behçet’s disease, according to study findings.
Researchers studied 101 patients with Behçet’s disease (BD), 74 patients with systemic lupus erythematosus (SLE), 44 patients with various systemic vasculitis and 101 healthy control participants matched to the patients with BD for age and sex. In each disease group, some of the patients received azathioprine at the time of or prior to the study whereas others did not.
A detailed medical history, including laboratory results from each participant, was collected. Plasma thiopurine S-methyltransferase (TPMT) was analyzed and compared among the participant groups. The highest levels were seen in patients with SLE (29.37 ng/mL), followed by patients with vasculitis (26.24 ng/mL), BD (22.8 ng/mL) and healthy participants (22.71 ng/mL). The only significant difference in plasma TPMT levels were seen between patients with BD and patients with SLE, according to the researchers.
Plasma TPMT levels were similar between patients who received azathioprine and participants who did not; however, among the eight patients who reported adverse events related to azathioprine, plasma TPMT levels were significantly lower compared with the other groups (14.08 ng/mL vs. 25.62 ng/mL). Three of the eight patients had levels of TPMT below the 11th percentile, and Chi-square analysis showed this group had a significantly higher risk for adverse events.
Further analysis showed a threshold level of 30 ng/mL or lower in patients with BD was associated with 100% sensitivity and 66% specificity, and a 28 ng/mL threshold was associated with 100% sensitivity and 43.4% specificity for adverse events among users of azathioprine. - by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosures.
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