Is the course of COVID-19 associated with tuberculin skin test diameter? A retrospective study.

Gulen, Tugba Arslan; Bayraktar, Muhammet; Keskin, Nese; Kayabas, Uner

The pathogenesis of COVID-19 is still not fully understood. Since SARS-COV-2 has a similar pathogenetic pathway to Mycobacterium tuberculosis, it has been reported that there may be a relationship between BCG vaccination rate and COVID-19 severity. This study investigated the relationship between tuberculin skin test (TST) induration diameter and the clinical course of COVID-19. Of 1963 adult patients who underwent TST, 76 patients with SARS-COV-2 infection confirmed by RT-PCR analysis of respiratory tract samples were included in the study. Relationships between COVID-19 clinical severity and TST positivity, induration size, and other clinical parameters were analyzed. Of the 76 patients, TST results were negative for 53 patients (69.7%) and positive for 23 patients (30.3%). COVID-19 severity was mild in 47 patients (61.8%), moderate in 22 patients (28.9%), and severe in 7 patients (9.3%). All TST-positive patients had mild disease. Patients with mild disease had significantly higher TST positivity rate (P<.001) and larger induration diameter (P<0.001). Area under the receiver operating characteristic (ROC) curve of TST induration size for the differentiation of mild with moderate and severe disease was 0.768 (P<.001). The maximum Youden J index value was 0.522 at an induration diameter of 6.5 mm, which had a sensitivity of 66.0% and specificity of 86.2%. COVID-19 patients with positive TST showed a significantly higher rate of mild disease than those with negative TST. TST positivity is favorably associated with the course of COVID-19. This article is protected by copyright. All rights reserved.