The Frequency of Thiopurine Methyltransferase Polymorphism in Systemic Lupus Erythematosus SLE

In this study, we observed adverse effects, TPMT polymorphism, and disease status.

Objective: Primary- to observe the frequency of thiopurine methyltransferase (TPMT) polymorphism and its effect on the use of AZA in SLE. Secondary - to determine the frequency of TPMT polymorphism in SLE with or without AZA-induced adverse effects, and to determine the frequency of adverse effects of AZA in SLE patients.

Methods and Materials: This observational nested case-control study was done in the Department of Rheumatology at Bangladesh Medical University and the Pharmacokinetics and Pharmacogenetics laboratory in the Department of Pharmacy at Dhaka University. The study period was July 2014 to January 2016. A total of 330 people were included in this study. The study population was SLE patients attending lupus clinics and inpatient clinics. A Convenient sampling procedure was used.

After receiving informed consent from the patient, those who fulfilled the updated 1997 revised ACR criteria of SLE were included in this study. The patient was unwilling to participate, had received a recent blood transfusion, had been administered any other myelosuppression drug, and had received treatment interfering with the metabolism of AZA or 6 MP, like allopurinol or diuretics. Concomitant treatment with cyclosporine, Mycophenolate Mofetil, and pregnancy were excluded from the study.

Flow chart of study procedure: Part A IRB Clearance

SLE patient (Fulfilling 1997 ACR Criteria)

Blood sample collection

Isolation of Lymphocyte

DNA isolation from lymphocyte

PCR and Identification of TPMT Gene

Part B:

Patient fulfilled indication of AZA Maintenance of remission of lupus nephritis, Neuro-psychiatric lupus, vasculitis, intolerance to steroid, associate with Defuse Parenchymal Lung Disease (DPLD) Starting AZA at a dose of 1 mg/kg/ body weight

First follow-up at 2nd week and change dose of AZA 2 mg /kg/ BW/day

Then Follow-up 4 weekly for total 12 week

Quality assurance strategy All the patients were selected very carefully from the SLE clinic and the inpatient department of BSMMU under the supervisor's guidance. The patients who were able to give their complete history will be interviewed only; those who were mentally unstable, very ill to give their history, or who lost their medical document will be excluded from the study. Information gathered from the patient was checked and rechecked with the medical record. To ensure the drug ingestion, we asked each patient to show the empty drug strip in every visit. Data collection per the questionnaire was scrutinized for quality assurance of interviewing and to check the standardization of the questionnaire. Any changes or corrections to the questionnaire and the data collection strategy were made per the guide's advice. A midterm evaluation of the study was done to check the consistency of data collection. In case of any incomplete data, we interviewed the patient again to get all the required information. Data cleaning was done before editing on the computer for analysis.

Ethical issues The nature and purpose of the study were explained in detail to all participants. The relevant investigation was done, and treatment was given to all subjects in this study. Informed and written consent was taken from every patient before enrollment. A unique identification number was provided to each patient. Each patient enjoyed every right to participate, refuse, or withdraw from the study at any point, but proper treatment will be ensured even then. Before starting this study, ethical clearance was taken from the Institutional Review Board (IRB), BSMMU. Data taken from the patients was regarded as confidential and kept locked under the principal investigator for purposeful use only.

Analysis After collecting information, all data were checked, verified for consistency, and edited appropriately. Simple descriptive measures like percentage, mean, and standard deviation of different variables were calculated. Variables were described as mean and standard deviation for quantitative data. The chi-square test was used to compare the prevalence of polymorphism alleles in SLE patients who received and did not receive AZA. The Mann-Whitney test was used for nonparametric data. A Z test was used to compare the proportion. The difference between means was compared using the Mann-Whitney U test. A p-value less than or equal to 0.05 was considered significant. All data analysis was done using the SPSS/PC statistical software package.