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.
Highlights
Rheumatoid arthritis by its pathogenesis and treatment associated, is an immunosuppressive state [1]
The prevalence of latent tubercular infection (LTBI) in a healthy Indian population as reported from various studies ranges from 9-80% [2]
Multiple studies had shown the effect of corticosteroids on TST reading in RA, other diseasemodifying anti-rheumatic drugs (DMARDs) did not seem to possess any effect on the same [8,9,10]
Summary
Rheumatoid arthritis by its pathogenesis and treatment associated, is an immunosuppressive state [1]. In tuberculosis (Tb) endemic country like India, this mandates essential screening for LTBI before initiating immunosuppression like biologicals [3]. TST is more cost-effective than IGRA and the clinical utility of both in immunosuppressed patients is debatable [4,5]. In early untreated rheumatoid arthritis, due to abnormalities in circulating T cells, reaction to an antigenic stimulus is hampered which can affect TST [6]. Various studies have shown variable TST response in RA – naïve RA patients had smaller TST reading compared to treated patients [7]. This study was planned to assess the prevalence of TST positivity in naïve as well as treated RA patients in a Tb endemic population and correlate with various factors that affect it
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