First insight into latent tuberculosis infection among household contacts of tuberculosis patients in Duhok, Iraqi Kurdistan: using tuberculin skin test and QuantiFERON-TB Gold Plus test.

BACKGROUND

The objectives were to estimate the prevalence of latent tuberculosis infection (LTBI) among household contacts (HHCs) with active TB patients, and to identify their risk factors.

METHODS

A prospective, cross sectional study was conducted from May to October 2018. All HHCs with active TB cases were included. The subjects underwent two tests: Quantiferon TB-Gold plus assay (QFT-Plus) and tuberculin skin test (TST). Data were analyzed using the Statistical Package for Social Sciences 25.

RESULTS

Among 521 HHCs, 101 (24.05%) revealed positive TST and 80 (19.85%) positive QFT-Plus. The significant risk factors associated with positive TST individuals were ≥ 15 years, immunosuppressive therapy, and pulmonary TB (PTB) patients; whereas, those with QFT-Plus positive were ≥ 45 years, alcohol consumption, and immunosuppressive therapy. The concordance rate among 309 individuals who performed both tests was 0.88 %; the kappa value showed good agreement (k = 0.679) and significant correlation (P < 0.001).

CONCLUSIONS

The overall rate of LTBI was intermediate. Screening of LTBI should be routine among HHCs, regardless of the site of the disease. Age ≥ 15 years, alcoholics, immunosuppressive therapy, and PTB were potential risk factors. There was a good concordance between TST and QFT-Plus. A QFT-Plus can overcome the limitation of a BCG vaccinated individual, especially in early life.