Introduction: Ankylosing Spondylitis is a chronic and progressive inflammatory disease of the spine and enthesis affecting skeletal and extra skeletal tissues and is largely associated with HLA B27. However, more than 95% of individuals in the general population with this gene never develop Ankylosing Spondylitis. A lot of studies have shown that HLA B27 reveals remarkable polymorphism with an ever-increasing number of alleles and atleast 105 subtypes of HLA B27 is now known. Correlating the severity of Ankylosing Spondylitis using ASDAS score with the presence of a particular subtype of HLA B27 can help in segregating a high-risk population and subjecting them to an aggressive and early onset treatment for greater therapeutic benefits and thus reducing the disability burden on the society.
Objective: To study the correlation between the disease severity and the HLA-B27 subtype associated. Thus, studying the influence of a particular HLA-B27 subtype on the disease severity that would be quantified using ASDAS.
Method: This is retrospective as well as a prospective study in which fifty consecutive patients of Ankylosing spondylitis of 16 years of age and older were recruited into the study along with Fifty healthy controls. HLA B27 typing and subtyping of all patients and controls was done by PCR Sequence specific primer method. Ankylosing Spondylitis Disease Activity Score (ASDAS) was determined using Clinical data of the patients and Erythrocyte Sedimentation Rate (ESR).
The frequencies of different HLAB27 subtype and its comparison with disease severity (ASDAS) were done using Chi-square test and one way Analysis of Variance test. Further, Bonferroni post hoc test was applied for multiple comparisons of each subtype. All statistical analyses were performed using SPSS for windows. Statistical tests were two sided and significant level with p< 0.05 was considered significant.
Result: Out of 50 patients of Ankylosing spondylitis, HLA-B27 was positive in 46 individuals (92%) in which the frequency of each subtype was: HLA B2705 (67.4%), HLAB2704 (17.4%), HLAB2702 (8.7%) and HLAB2707 (6.5%). Among the 2 healthy controls who were found to be HLAB27 positive, both of them were of HLAB2705 subtype. Further, One way Analysis of Variance and Post HOC test was used to determine statistical significant difference between the means of Ankylosing Spondylitis Disease Activity Score (ASDAS) for the each HLAB27 subtypes revealed that HLAB2704 is associated with a higher disease severity scores among its natives as compared to the other commonly found subtypes. Although, HLAB2705 by virtue of it being the commonest subtype found in our study was found in all the three severity groups, while HLAB2702 and HLAB2707 was associated with less severe disease states.
Conclusion: HLAB27 association with Ankylosing Spondylitis has been emphasized with HLA B2705 being more prevalent in Indian population. The correlation between the disease severity and the HLA-B27 subtype associated has been established with respect to HLA B2704 subtype .The study highlights that it is possible to predict the course of Ankylosing Spondylitis with the knowledge of the HLAB27 subtype of the patient.