Anti-cyclic Citrullinated Peptide as an early and accurate laboratory marker for the diagnosis of Rheumatoid Arthritis (RA) and the prevalence of HLA-B27 among Ankylosing Spondylitis patients in Ghana

Rheumatoid Arthritis (RA) and Ankylosing Spondylitis (AS) are two of the most common autoimmune diseases. This study aimed to obtain the best biomarker for early and accurate diagnosis of RA, determine the prevalence of HLA-B27 among AS patients in Ghana, and examine if there is dyslipidaemia and oxidative stress among them. A total of one hundred and sixty-seven (167) subjects were recruited for this cross sectional study from October 2006 to June 2008. They were made up of one hundred and two (102) RA and sixty-five (65) AS subjects. Both groups were recruited from the orthopaedic departments of Komfo Anokye Teaching Hospital (KATH), Korle-Bu Teaching Hospital (KBTH) and from subjects visiting MEDILAB centres nationwide with laboratory requests to investigate rheumatoid conditions. Those who were confirmed with either RA or AS and consented were recruited. Fifty (50) healthy blood donors with similar age and sex distribution as the subjects were recruited as control group. After ethical approval and informed consent had been obtained, information on socio-demographic characteristics and medical history were obtained from standardized questionnaires which was administered to them and through their medical records. Rheumatoid Factor (RF)-latex and its isotypes (RF-IgA and RF-IgM) were assayed and compared with anti-CCP as specific markers for early diagnosis of RA in Ghana. HLA-B27 was assayed to determine its prevalence among AS subjects. Lipid profile, Tumour Necrosis Factor-α (TNF-α) and Erythrocyte Sedimentation Rate (ESR) were estimated to determine the presence of dyslipidaemia and inflammation among AS and RA subjects. To evaluate the presence of oxidative stress, MDA and vitamin C were also determined among RA and AS subjects. Out of 102 RA subjects, Sensitivity was highest for RF-IgM test (58.45%) followed by anti-CCP antibody (54.34%), RF-latex (52.48%) and RF-IgA tests (28.51%). Specificity of 96.67% was obtained for anti-CCP, 69.52% for RF-IgM, 63.12% for RF-latex and 51.75% for RF-IgA. RA and AS subjects had a higher mean level of total cholesterol (TC) 5.88 ± 0.06 mmol/l. The difference between the RA and AS subjects’ cholesterol level and that of the control was significant (p<0.001) with a significant (r2= 0.0619, p= 0.002) positive correlation between serum triglycerides levels of AS and RA patients and that of the control. RA and AS subjects exhibited a slightly higher mean level of triglycerides 0.88 ± 0.16 mmol/l as compared to 0.56±0.05 mmol/l of controls. The difference between the subjects triglycerides levels and that of the control was significant (p<0.001). The mean HDL level for the patients was significantly lower (p<0.001) as compared to that of the control. The mean LDL level indicates a significantly higher (p<0.001) value as compared to that of the controls with a significant (r2= 0.0619, p= 0.002) positive correlation between serum triglycerides, total cholesterol, HDL and LDL of RA subjects. A significant (p<0.001) atherogenic ratios i.e. TC/HDL-C and LDL-C/HDL-C were observed among the subjects and controls. Out of 65 AS subjects examined there were four (4) HLA-B27 positives representing 4.6%, three (3) of the HLA-B27 positives were males, the mean Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score was 44.7/100. Forty-eight (48) AS patients had sacroilitis in their x-ray reports. None had a family history of AS or any extra-articular manifestations. TNF-α level among RA and AS patients were 11.87 ± 0.30 pg/ml and 13.11 ± 0.50 pg/ml respectively as compared to normal control of 5.70 ± 0.48 pg/ml whiles the mean ESR for AS was 34.64 ± 1.87 mm/hr and that of RA was 24.67 ± 1.87 mm/hr as compared to 9.23 ± 0.91 mm/hr of controls. The mean MDA level for AS subjects was 0.75 ± 0.03 mmol/l and that of RA subjects was 1.57± 0.06µmol/l as compared to normal controls of 0.58 ± 0.02mmol/l. MDA levels had a significant correlation with the serum levels of vitamin C. Vitamin C was 0.85 ± 0.03mmol/l for AS subjects and 0.95 ± 0.02mmol/l for RA subjects as compared to 1.12± 0.01µmol/l of control. This study has demonstrated that anti-CCP has the highest specificity and that the combination of anti-CCP and RF-IgM assay are highly specific and moderately sensitive for diagnosing RA, making this combination of autoantibodies a powerful tool in the serologic assessment of RA in Ghana. The presence of anti-CCP at disease onset means that they have a high positive predictive value of 100, a negative predictive value of 22.6 with 4.98 and 0.68 as positive and negative likelihood ratios respectively, predict the development of erosive joint lesions and the detection of these antibodies can therefore be used in clinical practice to help plan a therapeutic strategy. Findings from this study further showed that HLA-B27 is present in some AS patients. The BASDAI scores and other clinical features clearly denote the presence of the disease with moderate disease activity. Dyslipidaemia is present in early RA and AS subjects, and that proinflammation and inflammation markers plays a pivotal role in the development of atherosclerosis as evidenced in the increase in TNF-α, ESR and a more atherogenic lipid profile, thereby increasing cardiovascular risk. Increased oxidative stress is evidenced by raised MDA and decreased vitamin C and that lipid peroxidation is a giant distracter in RA and AS.

Source: KNUST