Positivity rate of QuantiFERON-TB Gold Plus ^® test among candidates for biotherapy and factors influencing results

Background: Latent tuberculosis infection, an infection caused by Mycobacterium tuberculosis , affects one-quarter of the world’s population. The World Health Organization recommends screening for latent tuberculosis infection in at-risk populations to reduce morbidity and mortality risks associated with tuberculosis using the tuberculin skin test and interferon-gamma release assays, including the QuantiFERON-TB Gold Plus ® test (QTF-Plus ® test). Objectives: This study aimed to assess the place of QTF-Plus test in latent tuberculosis infection screening among a high-risk population. Methods: A total of 969 biotherapy candidates were included in the study (52.63% female and 47.36% male; sex ratio = 0.9). Results: The mean age was 38.29 ± 15.83 years. The frequency of latent tuberculosis infection, according to QTF-Plus test results, was 20.22%. Factors such as age and history of tuberculosis were significantly associated with QTF-Plus test results ( p = 0.002 and p < 0.0001, respectively). QTF-Plus test and tuberculin skin test were performed simultaneously on 632 patients. A weak agreement between these tests was found (77.50%, Cohen’s kappa coefficient of 0.13). However, a good correlation between TB antigen tube 1 and TB antigen tube 2 ( r = 0.72, p < 0.0001; 95% CI: 0.68–0.74) was observed. Conclusion: Our findings demonstrate that the QTF-Plus test is useful for latent tuberculosis infection screening in a highly vaccinated population with an intermediate prevalence of tuberculosis