We would like to address some questions that were raised about our recently published study on the prevalence of latent tuberculosis infection (LTBI) in patients with interstitial lung diseases (ILDs) requiring immunosuppression.(1)
 
The prevalence of LTBI in our sample (9.1%) was indeed lower than that estimated for the world population (about 25%). It should be noted, though, that Kussen et al.(2) reported a similar prevalence (9.0%) in people living with HIV, a known high-risk group, in a study that also took place in the state of Paraná, Brazil, where our center is located, which might reflect a different scenario of infection by Mycobacterium tuberculosis in our region.
 
As for the use of tuberculin skin test (TST) as a screening method, we considered it a plausible choice, given that there is no consensus on a preferred method for immunocompromised patients.(3) Interferon-gamma release assays could be a reasonable choice for these patients, especially when the TST is negative; however, despite having recently been incorporated into the Brazilian public health care system, they are not available for patients with ILDs requiring immunosuppression.
 
Regarding risk factors for tuberculosis, we excluded patients with high-risk factors, such as those living with HIV, and we found that the frequency of positive TST results was not significantly higher in those with a history of smoking or diabetes. Nevertheless, we acknowledge that other variables associated with a higher risk of tuberculosis, such as recent contact with someone with the disease, were not addressed in our study. Moreover, we reinforce that patients with a positive TST result underwent not only clinical and radiological evaluation for active tuberculosis, but also microbiological evaluation whenever possible.
 
Finally, the lack of consensus on the need to treat LTBI in patients on immunosuppressants other than TNF inhibitors could be justified by the fact that the literature on the subject is scarce.
 
In conclusion, we agree that more studies are needed to determine the prevalence of LTBI in patients with ILDs effectively and to decide whether these patients should be prescribed preventive treatment. However, our study definitely marks a starting point to answering these important questions.
 
REFERENCES
 
1.            Dias VL, Storrer KM. Prevalence of latent tuberculosis infection among patients with interstitial lung disease requiring immunosuppression. J Bras Pneumol. 2022;48(2):e20210382. https://doi.org/10.36416/1806-3756/e20210382
2.            Kussen GM, Dalla-Costa LM, Rossoni A, Raboni SM. Interferon-gamma release assay versus tuberculin skin test for latent tuberculosis infection among HIV patients in Brazil. Braz J Infect Dis. 2016;20(1):69-75. https://doi.org/10.1016/j.bjid.2015.10.007
3.            Hasan T, Au E, Chen S, Tong A, Wong G. Screening and prevention for latent tuberculosis in immunosuppressed patients at risk for tuberculosis: a systematic review of clinical practice guidelines. BMJ Open. 2018;8(9):e022445. https://doi.org/10.1136/bmjopen-2018-022445