21st European Congress of Clinical Microbiology and Infectious Diseases

Diagnosis of tuberculosis infection in health care workers. Comparison of tuberculin skin test with QuantiFERON TB Gold In-Tube

Abstract number: R2687

Perez Escolano E., Gutierrez J., Menor E.M., Lopez M.I., Bernal C., Alados Arboledas J.C., Lopez-Prieto M.D.

Objectives: To compare the use of tuberculin skin test (TST) and Interferon-g (IFN-g) Release Assay using three specific antigens (ESAT-6, CFP-10 and TB7.7) (QuantiFERON^®-TB Gold in tube) for the diagnosis of tuberculosis infection (TBI) and indication of treatment in health care workers.

Methods: We conducted a prospective transversal study of health personnel who came for routine health care study (may 2007 to june 2010). All were screened with TST and QFT (Cellestis, Australia) and risk factors were registered in a questionnaire. Patients with a positive result (TST or QFT) were screened also with chest X-ray. TST was performed by Mantoux method and a positive test was defined as an induration 5mm in non-vaccinated and 15 mm in vaccinated people. QTF was made according to the manufacturer specifications. We considered as vaccinated persons those presenting with a suggestive scar. CDC recommendations were followed for the interpretation of the QFT. Agreement between TST and QFT was assessed by the Cohen kappa coefficient.

Results: We studied 316 health care workers (72.2% women) from the General Hospital of Jerez. Average age was 43.4 years (SD: 8.8), 76.4% had been vaccinated with BCG. TST was not done in 104 (32.9%) persons because of a previous positive TST. TST was positive in 50 (68.5%) and QFT in 30 (41.1%) non-vaccinated people. Whereas, for vaccinated people TST was positive in 93 (39.1%) and QFT was positive in 53 (22.2%). Agreement between the TST and QFT was 64.4% (Kappa 0.33, CI (0.15–0.51)) among the non vaccinated group; when we defined positive test for TST as an 10 mm induration, agreement was 71.2% (Kappa 0.43, CI (0.23–0.63). Agreement was 64% (Kappa 0.18, CI (0.06–0.30)) for the vaccinated group. Two indetermined results were detected by QFT. The indication of TBI treatment made by TST and risk situation was modified in 70% of cases according to QFT test. We prescribed treatment of TBI by QFT in 13% of the patients that did not have this indication according to the TST.

Conclusions:

1Agreement between TST and QFT was low in vaccinated and non-vaccinated people.

2QFT was better than TST for recent tuberculosis infection diagnosis in health care workers because of its high specificity and no interference of booster

3QFT was a better indicator for treatment of tuberculosis infection.

Further studies addressing IFN-g sero-conversion and -reversion in health care workers for the follow-up of health care personnel are needed.