Value of the HLA-DRB1 shared epitope for predicting radiographic damage in rheumatoid arthritis depends on the individual patient risk profile

Objective. To investigate the influence of individual patient risk profiles on the value of the HLA-DRB1 shared epitope (SE) as a predictor of severe erosive damage in rheumatoid arthritis (RA). Methods. Patient characteristics, clinical signs and symptoms, rheumatoid factor (RF) status, and HLA-DRB1 genotypes were available for 154 Caucasian women with RA. Risk profiles were defined by nongenetic factors that predict severe erosive disease. The additional value of the SE was defined by the likelihood ratios (LR) of SE presence and absence, which were calculated at the individual patient level. Results. In the total population, the LR of SE presence was 1.42 and the LR of SE absence was 0.37, corresponding to an odds ratio of 3.9, indicating a substantially higher risk of severe erosive disease in those with the SE compared to those without. The LR of SE presence and absence varied depending on the risk profile of the women, from 1.01 to 2.25 for SE presence and 0.22 to 0.49 for SE absence. Considering all the patient characteristics, SE status was most significantly related to RE status. Consequently, the LR of SE presence and absence were higher for RF-negative women compared to RF-positive women (SE presence 1.77 vs 1.40, p < 0.001 and SE absence 0.38 vs 0.30, p < 0.001). Conclusion. The additional value of SE testing for predicting severe erosive disease varies according to patient risk profiles. Given the likely availability of genetic and other novel tests in the future, information about the additional value of test results is needed to ensure the optimal use of such testing in the management of RA.