Assessment of latent tuberculosis infection in psychiatric inpatients: A survey after tuberculosis outbreaks.

BACKGROUND/PURPOSE: To investigate risk factors of latent tuberculosis infection (LTBI) among inpatients of chronic psychiatric wards with tuberculosis (TB) outbreaks.

METHODS

In April 2013, inpatients of four all-male wards with TB outbreaks were tested for LTBI using the QuantiFERON-TB Gold in Tube (QFT) method. Based on this investigation, a retrospective study was conducted to assess risk factors for LTBI. Inpatients exposed to cluster-A or cluster-B TB cases were defined as contacts of cluster-A or cluster-B, and others, as nonclustered contacts.

RESULTS

Among 355 inpatients with TB exposure, 134 (38%) were QFT-positive for LTBI. Univariate analysis showed that significant predictors for QFT-positivity were age, case-days of exposure to all TB cases (TB-all) and to sputum smear positive cases, number of source cases with cough, and exposure to cluster-A TB cases. Independent risk factors for LTBI were higher age [adjusted odds ratio (OR) 1.03, 95% confidence intervals (CI: 1.01-1.05)], TB-all exposure case-days ≥ 200 [adjusted OR 2.04 (1.06-3.92)] and exposure to cluster-A TB cases [adjusted OR 2.82 (1.30-6.12)] after adjustment for the sputum smear positivity, and cough variables of the source cases. The contacts of cluster-A had a greater risk of LTBI than did those of cluster-B, especially in the younger population (≤50 years) after adjustment [adjusted OR 2.64 (1.03-6.76)].

CONCLUSION

After TB outbreaks, more than one third of inpatients were QFT-positive for LTBI. Our findings suggest that, beside the infectiousness of source cases, intensity of exposure, and age of contacts, exposure to TB cases in potential genotyping clusters may be predictive for LTBI in this male psychiatric population.