The occurrence of anticardiolipin antibody isotypes in the Malaysian population with systemic lupus erythematosus Lay Kim Tan1, Masita Arip1, Chun Lai Too1, Yee Ming Ching1, Norhazlin Mustafa1, , Mohammed Faizal Bakhtiar1, Mohd Farid Baharin1, Noormalin Abdullah1, Ainur Yusniza Yusof1, Aliah Tawil1, Salmay Wahid1, Jasbir Singh Dhaliwal1, and Shahnaz Murad2. 1Allergy and Immunology Research Center, Institute for Medical Research, Kuala Lumpur. Malaysia. 2Institute for Medical Research, Kuala Lumpur. Malaysia. INTRODUCTION Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease that commonly affects female. Previous studies showed that ACL was associated with the genesis of thrombosis, thrombocytopenia, pulmonary hypertension and spontaneous abortions in SLE. SLE has a wide range of clinical manifestations and can affects the skin, joints, kidney, lung, brain, and the nervous system. Anticardiolipin antibody (ACL) is one of the antiphospholipid antibodies that interferes the normal function of blood vessels which leads to vasculopathy and thrombosis. OBJECTIVES MATERIALS AND METHODS In this study, we investigated the presence of anticardiolipin antibody isotypes among Malaysian patients with SLE. The association between anticardiolipin antibody and clinical manifestations in Malaysian patients with systemic lupus erythematosus was investigated. The clinical data of a total of 475 patients with SLE were analyzed retrospectively from our diagnostic service laboratory. The ratio of female to male patients with SLE was 23:1. The age of the patients ranged from 19 to 66 years with the mean age of 31.2±10.2 years old. Blood samples were collected in plain tubes. Sera were screened for anticardiolipin antibody. The age, gender, ethnicity and clinical data of the SLE patients were analyzed. The frequencies of the aCL antibodies isotype in SLE patients from different ethnicities were analyzed. The association of the aCL antibody with clinical manifestations were analyzed using Pearson’s chi square test. Fig 1. The distribution of SLE cases by ethnicity RESULTS The presence of ACL was detected in 88 individuals (18.5%) with SLE (Fig 2). IgG ACL isotype contributed significantly to the total number of ACL-positive SLE cases (OR=5.90; 95% CI=3.4-10.2; p <0.05). Nine individuals had both the IgG and IgM ACL isotypes. The frequency of IgG ACL in ACL-positive individuals was highest in Indian (100%) followed by Malay (91.9%) and Chinese (85.6%) (Fig 4). Interestingly, IgM ACL was found more commonly in Chinese (30.8%) in this ACL- positive patients group compared to Malays (14.5%) and Indians (20%). Fig 4. The distribution of ACL antibody isotypes in ACL antibody-positivity group in different ethnicities. Fig 2. The distribution of ACL isotypes. The frequencies of the ACL in our 3 major ethnic groups were not proportional to our ethnic distribution, where Malays comprised the largest number by ethnicity in Malaysia (Fig 3). Our study revealed highest occurrence of ACL (30.3%) in Indians compared to the Malays (19.6%) and Chinese (16.3%) (Fig 3). The analysis of the clinical manifestations revealed the highest frequency of skin rash (29.7%) followed by renal (17.7%) and neurology (13.5%) (Fig 5). Our analysis indicated an association between renal disease with ACL-positive in Malaysian patients with SLE (OR=1.61, 95% CI=0.92-2.82 p=0.092). Fig 3. The distribution of ACL antibody isotypes in different ethnicities. Fig 5. Clinical manifestation in SLE patients. CONCLUSION IgG ACL antibody isotype was found to be common among Malaysian SLE patients. Highest proportion of IgG ACL antibody was found in the Indian patients with SLE. ACKNOWLEDGEMENT We would like to thank the Director General of Health, Ministry of Health Malaysia and Director of IMR for their approval to present the current work. Special thanks to all the staff from Autoimmune Unit, AIRC, IMR for their technical assistance in the laboratory. Tan Lay Kim Allergy and Immunology Research Center, Institute for Medical Research, 50588 Jalan Pahang, Kuala Lumpur. Tel : +603 2616 2587 E-mail : tanlk@imr.gov.my