Background Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease. People with rheumatoid arthritis are more prone to atherosclerosis due to chronic inflammation and improving survival. However, in recent years, cardiovascular and cerebrovascular mortality rates have been found to be higher in RA patients than in the general population1. Oxidation of low-density lipoprotein (LDL) to Oxidized-LDL (ox-LDL) may be an important event in the development of atherosclerosis.
Objectives To determine serum levels of oxidized-LDL levels in patients of RA and to determine correlation between ox-LDL and disease activity (DAS28).
Methods We conducted a descriptive observational case control study of 30 cases of RA who fulfilled RA definition by 1987 American cardiology association (ACR) criteria and all were age and sex matched to healthy controls at 1:1 ratio. The patients with Diabetes mellitus, hypothyroidism, morbid obesity, known dyslipidemia, chronic kidney disease, chronic liver disease, known case of atherosclerotic disease and active smoker were excluded from the study. All the cases and controls were evaluated for serum ox-LDL level by Enzyme Linked Immunosorbent Assay (ELISA). A dose response curve of the absorbance unit vs. concentration is generated using result obtained from the calibrators. Concentration of ox-LDL (microgram/ml) present in the serum sample were directly determined from this curve. The disease activity was measured by DAS28ESR in RA patients. The statistical analysis was done using Microsoft excel 2007 and SPSS version 19. The variables were taken as mean ± SD, Unpaired students t test was used to compare normally distributed groups. The P value of <.05 was taken as significant. Pearson correlation was used to correlate serum ox-LDL and disease activity (DAS28).
Results The study included 30 RA patients with mean age 43.13±13.32 yrs while the mean age of control group was 42.87±15.03 (p>0.5). Both the study group predominantly consisted of female 26/30 and they were sex matched with control population. The ox-LDL (microgram/ml) was significantly higher in RA cases (9.038±6.119) versus control (3.005±2.673) (P<0.0001). The DAS-28 score was found to be high among 27 cases in a range of severe disease activity (>5.1), while in three cases it was found that the disease activity was in moderate range (3.2-5.1). This may be due to recruitment of early DMARD naïve patient. No significant correlation was found between ox-LDL to DAS-28 by Pearson correlation (p=0.867).
Conclusions In our study we found that ox-LDL was significantly higher (p<0.0001) in RA patients compared to age and sex matched controls similar to other studies2. We did not find any correlation between the DAS28(ESR) and ox-LDL in our study, this may be due to small sample size or high DAS28 scores of most of the patients. The serum ox-LDL can be a useful future atherosclerotic marker for detecting subclinical/early atherosclerosis.
Avina-Zubeta JA et al. Arthritis rheum. 2008. 59(12): 1690-1697
Vuilleumier N et al. Scan J Rheumatol. 2010; 39(6): 447-53.
Acknowledgements Dr Ritu Singh for providing Lab support for doing Oxidized LDL.
Disclosure of Interest None declared