Utility of tuberculin skin test and QuantiFERON TB gold-plus in the screening of latent tuberculosis infection in refractory spondyloarthritis patients

ABSTRACT

Background: Reactivation of latent tuberculosis infection is a major concern prior to initiation of biologics or tsDMARDs in refractory spondyloarthritis (SpA) patients. This study was carried out to observe the utility of TST and QFT-Plus among BCG vaccinated refractory spondyloarthritis patients in Bangladesh. Methods: A total of 51 consecutive refractory SpA patients of both genders were enrolled from July 2019 to July 2020 in the department of Rheumatology, BSMMU, Dhaka. All patients were evaluated clinically and by laboratory tests. Chest x-ray, QFT-Plus and TST were done in all patients. For COVID-19 pandemic, estimated sample could not be enrolled. Therefore, a model based simulation test was used to convert the 51 primary data to 97 simulated data using R software with arm' and Himise package to observe the changing trends of results. By observing simulated outcomes researchers can gain insight on the real world. Agreement between TST and QFT-Plus was evaluated using kappa statistics. To identify variables associated with TST or QFT-Plus results bivariate analysis was done. Results: The mean age in years was 35.16 ± 11.24. Number of male and female were 39 (76.5%) and 12 (23.5%) respectively and ratio was 3.251. Among the enrolled subjects TST was positive in 5 (9.80%) patients and in simulation model positivity become 12 (12.37%). On the other hand, out of 51 subjects, 8 (15.58%) was QFT-Plus positive and in simulation model positivity turned out 16 (16.49%). Agreement between TST and QFT-Plus was poor;kappa value was 0.39 in primary data and 0.33 in simulated data. In simulated data female gender was associated with QFT-Plus positive results [Odd Ratio (OR) = 4.1;95% Confidence Interval (CI) = 1.38-12.76;p = 0.01]. Conclusion: QFT-Plus may be preferable than TST in the screening of latent tuberculosis infection in refractory SpA patients.