Background Leading causes of death in systemic lupus erythematosus (SLE) are infections, kidney failure and cardiovascular disease. Although most infections are bacterial, there is a greater prevalence of tuberculosis (TB) secondary to multiple immunological abnormalities and immunosuppression. The tuberculin skin test (TST) and chest radiography are not sufficient to detect latent TB infection (LTBI) in this group of patients. Currently interferon-Yrelease assay (IGRAS): Quantiferon-TB Gold In-Tube ™ (QFT-GIT) and T-SPOT.TB ™ (T-Spot), have shown greater superiority to diagnose LTBI in immunocompetent patients but efficiency is unknown in immunosuppressed patients with SLE.
Objectives The objective of the present study is to evaluate the efficiency of IGRAS in screening for LTBI in patients with SLE.
Methods We performed a cross-sectional study that included patients with SLE according to the ACR criteria, ≥ 16 years old and signed informed consent; pregnant patients were not included, nor with active TB or with antituberculosis treatment. Patients underwent a questionnaire to obtain epidemiological and clinical data of SLE and TB, and TST and IGRAS were performed. The statistical analysis included descriptive arithmetic, chi square for categorical variables, Student’s t test for quantitative variables and kappa for concordance.
Results We reviewed a total of 106 patients with SLE, with a mean age of 34.7 ± 13.2 and 95% were female. A history of BCG was found in 90% and 84% presented a scar. Only 8% reported contact with TB patients and 12% were employees or residents of health or correctional institutions. A previous PPD was reported in 8%, of which 11% had a positive result. The 4% with previous diagnosis of TB had received treatment, 75% with lung and 25% with kidney involvement. Comorbidities: 28.3% with hypertension, 2.8% diabetes mellitus and 16% with dyslipidemia. In the present study 9% had a positive PPD, with an average of 5.53 ± 1.92 mm. The QFT-GIT test reported 14% positive, 10% indeterminate and 76% negative. The latter test average was 1.77 ± 0.68 IU / ml in general, 3.14 ± 2.85 in the group of patients with a positive test, 1.41 ± 3.04 in the indeterminate and 0.11 ± 0.11 in the negative group. A correlation between positive results of the two tests was 0.24.
Conclusions In our group of patients with SLE a significant number of positive tests was observed for the diagnosis of LTBI, finding a fair concordance between the two tests, but a large number of indeterminate tests were seen. Further studies are needed to determine the usefulness of these tests in SLE and the need for a lower cutoff of IGRAS in this type of patient.
References: Centers for Disease Control and Prevention. Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection — United States, 2010. MMWR 2010; 59: 1-26
Prabu V, Agrawal S. Systemic lupus erythematosus and tuberculosis: A review of complex interactions of complicated diseases. J Postgrad Med 2010; 56: 244-50
Disclosure of Interest: None Declared