Classification of participants
Following clinical and diagnostic work-up, the patients were assigned to one of the five categories:
1. ATB diagnosed in symptomatic patients with microbiologically confirmed TB (mATB) (positive microscopy, PCR or culture result), or in patients fulfilling ≥ two of the following three criteria: 1) clinical symptoms suggestive of ATB, 2) radiological findings consistent with ATB, and 3) a history of contact with PTB; all in conjunction with a positive clinical response to antituberculous treatment.
2. LTBI defined as a positive TST and/or IGRA result in asymptomatic children with a history of contact with PTB and a normal chest X-ray.
3. TB contacts – asymptomatic children with a history of contact with PTB, not fulfilling the criteria for ATB or LTBI.
4. non-TB – children with clinical suspicion of TB, but with other final diagnosis and a positive response to specific treatment.
5. controls – asymptomatic children after careful exclusion of TB contact and inflammatory comorbidities, and with negative IGRA result.
For simplicity reasons, the term “Mtb.- infected” refers to children with LTBI and ATB combined together and “Mtb.- uninfected” to TB contacts, non-TB group, and controls combined together.