IFNgamma and antibody responses among French nurses during a tuberculosis contact tracing investigation

Study

A comparative study which compared PPD skin testing inserted according to the French Society of Pneumology's recommendations and interferon gamma release assay (IGRA) (QuantiFERON^® TB Gold In-tube, QF–TB–IT, Cellestis, Carnegie, Australia) was performed during a tuberculosis contact investigation in our hospital.

Patients

Nineteen French health-care workers (HCWs) volunteered to participate. All of the HCW enrolled were BCG vaccinated and had a normal chest X-ray at entry.

Results

Among the HCW, 68.4% were TST positive. By comparison, only 31.6% had a positive QF-TB-IT result. We took advantage of the negative tube and the corresponding plasma for antibody detection by ELISA. None were ELISA positive. Fourteen HCWs were followed up. None of the HCWs accepted a course of antiTB chemoprophylaxis. Despite the difficulty in establishing a trend in kinetics, we saw the complexity of interpretation of a dynamic T-cell response after contact with an index case.

Conclusion

This initial and first French picture provides us with the observation that only 44% of TST-positive HCW were IGRA positive, and the IGRA test allowed the detection of LTBI in two TST negative HCWs.