Thiopurine S-methyl Transferase (TPMT) Enzyme Level in Healthy Sudanese Population

Background: Thiopurine drugs have limited use due to their toxicity, related to the enzyme thiopurine S-methyl transferase (TPMT) activity, which varies between individuals. This is the first study in Sudan, which aimed to assess the TPMT phenotypic status of healthy Sudanese volunteers. Methods: A total of 177 healthy volunteers from Sudan were included in the study. TPMT enzymatic activities were measured using the ELISA serum protocol. We used SPSS to analyze the data and determined enzyme level categories and normal range with Z scores and quartile tests. The Sudan Medical Specialization Board (SMSB) Ethical Committee approved the study. Results: There were 117 males and 60 females among the volunteers, with ages ranging from 16 to 70 years and a mean age ± SD of 28.0 ±1 0.2, median = 24. Most candidates were from the Afro-Asiatic linguistic group (64.5%), followed by Nilo-Saharan (18.6%) and Niger-Kordofanian (16.9%). The TPMT enzyme level ranged between 0.17 and 9.5 ng/ml, with a mean of 2.26 ± 0.75 ng/ml. The quartile classification included very low enzyme (<0.76 ng/ml) seen in 4 candidates (2.3%), intermediate low (0.76-1.4 ng/ml) seen in 34 (19.2%), the normal range (1.5 – 3.75 ng/ml) seen in 119 (67.2%), and high enzyme activity (>3.76 ng/ml) seen in 20 (11.3%). No significant correlations between age, sex, and ethnic groups were recorded. Conclusion: The normal TPMT enzyme activity is between 1.5 and 3.76 ng/ml. A higher prevalence of TPMT deficiency was recorded and compared with international studies. Pretreatment screening using serum ELISA test for TPMT enzyme activity should be used to predict the risk of toxicity.