Prevalence Of Tuberculin Skin Test Positivity In Patients Of Early Rheumatoid Arthritis- Study from a tertiary care centre in North India.

Abstract

Objective: To assess the prevalence of tuberculin skin test (TST) positivity in early rheumatoidarthritis patients (< 6months disease duration) using Tuberculin sensitivity testing in a TB endemiccountry. Method: Included in this cross-sectional study were 200 patients of early rheumatoidarthritis divided into three groups- treatment naïve, patients on methotrexate only andmethotrexate plus low dose corticosteroids. 1TU (0.1ml) of PPD RT-23 with tween 80 was injectedintradermally over the left forearm and the induration measured after 72 hours. For interpretation,Induration >10mm was taken as positive, < 5mm as negative and 5-10mm as indeterminate.Healthy controls were taken for comparison. Results: 200 early RA patients and 60 healthy controlswere included in this study. The median age of the study population was 43 years (IQR 33-51) witha mean disease duration of 3.4 ± 2.1 months. 54 patients (27%) with early RA and 22 healthycontrol (36.7%) had TST positive (p=0.1). The mean TST positivity inpatient cohort was7.25±6.53(mm) and in the control population(mm) was 7.06±6.07.TST was positive in 26 (22.6%)treatment naïve patients (n= 115);22 (37.9%) patients on methotrexate(n=58) and 6 (22.2%)patients on methotrexate and low dose corticosteroids(n=27) (p=0.08). Prior BCG vaccinationstatus, disease activity, a dose of methotrexate and rheumatoid factor seropositivity had nosignificant effect on TST positivity. Conclusion: Tuberculin positivity is low among patients withearly RA as compared to the general population. The use of low dose steroids or methotrexatedoesn’t affect the tuberculin anergy. Further larger studies with augmented tuberculin doses arerequired to assess the factors affecting TST positivity in RA patients.