Serial testing of Malaysian health care workers with QuantiFERON®-TB Gold In-Tube

BACKGROUND: Serial testing for tuberculosis (TB) exposure has been advocated among health care workers (HCWs) at risk of nosocomial infection.
OBJECTIVE: To determine the incidence and factors associated with TB infection among selected HCWs in Malaysia and to determine interferon-gamma response in serial testing.
DESIGN: A cohort of 769 HCWs were retested after 1 year using QuantiFERON®-TB Gold In-Tube. Incidence of TB infection was determined among HCWs who previously tested negative. Conversion and reversion rates using several definitions were explored.
RESULTS: Incidence of TB infection was 9.9 per 100 workers per year (95%CI 7.9-12.3). Working in the Emergency Department (ED; RR 2.18, 95%CI 1.07-4.43) was significantly associated with risk of TB infection. Reversion and conversion occurred frequently, with 46.7% reversion among HCWs with baseline interferon-gamma (IFN-γ) levels of 0.35-0.70 international units (IU)/ml, and 23.8% conversion among HCWs with baseline IFN-γ levels of 0.20-0.34 IU/ml.
CONCLUSIONS: TB infection control measures need to be strengthened, particularly in the ED, as the incidence of TB was high. Conversion and reversion rates in serial testing were high, and further studies are needed to facilitate its interpretation.