Background Screening for latent tuberculosis infection is mandatory for juvenile idiopathic arthritis (JIA) children who are candidates for anti-TNF therapy¹. Although tuberculin skin test (TST) is still the most used tool for this purpose, it may have some limitations such as lower sensitivity in patients with impaired cellular immune function due to disease activity² or concomitant drug therapy^1.

Objectives To evaluate tuberculin skin testing (TST) response in juvenilie idiopathic arthritis (JIA) patients.

Methods Cross-sectional study including JIA patients (2004 ILAR criteria)³ and healthy sex and age matched controls in a single terciary center. Inactive disease was considered according to physician's global assessment and in the absence of arthritis, uveitis and systemic symptoms, allied to normal ESR or CRP⁴. The TST was performed by the Mantoux method and considered positive if induration ≥5 mm.

Results Among 75 JIA patients evaluated, 47 were females and mean age was 13.33±5.97 years. Similar percentages of positive TST were observed for patients with JIA and controls (14.7% vs 36.4% respectively, p=0.09). There were no differences when comparing patients with positive and negative TST, including age (15.65±5.02 vs 12.93±6.00 respectively, p=0.157), duration of disease (7.62±5.59 vs 6.39± 5.2, p=0.508), disease activity (63.3% vs 68.9%, p=0.736), AIJ subtypes (p=0.52) and intake of metothrexate (81.8% vs 70.3% respectively, p=0.717), leflunomide (0 vs 6.3%, p=1), cyclosporine (9.1% vs 21.9, p=0.445), sulfassalazine (9.1% vs 9.4%, p=1) and hidroxichloroquine (54,5% vs 22%, p=0.071). However, TST negative patients received significantly higher steroid dosages than patients with positive TST (13.10±14.90 mg/day vs 5.0±0 mg/day, respectively, p=0.022).

Conclusions The presence of similar responses to TST in controls and patients with JIA, independent of age, disease subtype, activity, and DMARD's, added to the history of exposure to active TB, is still a reliable tool for screening latent tuberculosis. However, in patients under prednisone dosage ≥13 mg/day, TST result should be interpreted with caution. Based in our results, we suggest screening of latent tuberculosis before starting steroids therapy in JIA patients.

References

1. Lalvani A, Millington KA. Screening for tuberculosis infection prior to initiation of anti-TNF therapy. Autoimmun Rev. 2008;8(2):147-52.

2. Camlar SA, Makay B, Appak O, Appak YC, Esen N, Gunay T, et al. Performance of tuberculin skin test and interferon gamma assay for the diagnosis of latent tuberculosis infection in juvenile idiopathic arthritis. Clin Rheumatol. 2011;30(9):1189-93.

3. Petty RE, Southwood TR, Manners P, Baum J, Glass DN, Goldenberg J, et al. International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol. 2004;31(2):390-2.

4. Wallace CA, Ruperto N, Giannini E, Childhood A, Rheumatology Research A, Pediatric Rheumatology International Trials O, et al. Preliminary criteria for clinical remission for select categories of juvenile idiopathic arthritis. J Rheumatol. 2004;31(11):2290-4.

Disclosure of Interest None declared