Long-term occupational risk of latent tuberculosis infection in Hamburg, Germany: Findings from a 13-year prospective observational study

Background

Only limited population-based data are available on the risk of latent tuberculosis infection (LTBI) in health care workers (HCWs).

Objective

To assess the long-term effects of protective measures of HCWs on LTBI risk in Hamburg, Germany.

Methods

Close contacts of smear-positive and smear-negative, but culture-confirmed, pulmonary TB index cases were prospectively enrolled from June 2005 to December 2017 and tested with the QuantiFERON TB (QFT) test approximately eight weeks after last exposure. Sociodemographic and clinical data were collected by trained healthcare personnel using a standardized questionnaire.

Contacts with known previous positive TST or IGRA results were excluded.

Results

After exclusion of prevalent TB cases and contact persons who had been tested positive in other settings, valid results were available for 937 index cases and 6980 close contacts (average per case 7.45; standard deviation (SD) ± 9.99; range 1–83). Of the contacts, 3459 (49.6 %) were males and 3520 (50.4 %) females. 771 contacts (11.05 %) belonged to 11 HCW subgroups, most of them (475, or 62.8 %) hospital or geriatric nurses. Foreign-born HCW did not differ significantly from non-HCW regarding origin from high-incidence countries.

By adjusting for confounders, logistic regression analysis confirmed household contact as strongest predictor for acquiring LTBI (OR 3.8, p < 0.001), followed by foreign-born status (OR 2.2, p < 0.001) and male gender (OR 1.28, p < 0.001). Contact with a smear-positive index case only slightly increased the risk of IGRA positivity, by 16 % (OR 1.16, p = 0.024). For each additional year of age, higher odds were found at 1.86 % (OR 1.019, p < 0.001] and for each additional hour of contact at approximately 0.11 % (OR 1.011, p < 0.001). BCG vaccination had no significant effect on IGRA test results (OR 0.95, p = 0.41).

Employment in healthcare overall was associated with a 26 % lower risk of IGRA positivity compared to non-HCWs (OR 0.74, p = 0.013); however, in a second adjusted model focusing on specific HCW subgroups, this risk reduction was statistically significant only for hospital and geriatric nurses, with no significant difference observed in other HCW subgroups.

Conclusion

Working in a health-care facility overall was associated with a lower LTBI risk compared to other risk factors. These findings suggest that protective measures might be particularly effective in hospital and geriatric nursing, while no risk reduction was evident for other HCW subgroups. Continued targeted protective measures remain important in high-risk care environments and support the relevance of recommendations issued (and last updated 2023) by the German Central Committee against Tuberculosis (DZK).