Evaluation of the tuberculin skin test and the interferon-[gamma] release assay for TB screening in French healthcare workers

• Published in: Journal of occupational medicine and toxicology (London, England) Vol. 4; p. 30
• Main Authors: Tripodi, Dominique, Brunet-Courtois, Benedicte, Nael, Virginie, Audrain, Marie, Chailleux, Edmond, Germaud, Patrick, Naudin, Frederique, Muller, Jean-Yves, Bourrut-Lacouture, Ma, Durand-Perdriel, Marie-Henriette, Gordeeff, Claire, Guillaumin, Guyonne, Houdebine, Marietherese, Raffi, Francois, Boutoille, David, Biron, Charlotte, Potel, Gilles, Roedlich, Claude, Geraut, Christian, Schablon, Anja, Nienhaus, Albert
• Format: Journal Article
• Language: English
• Published: BioMed Central Ltd 30-11-2009
• Subjects: Biological assay; Care and treatment; Diagnosis; Health aspects; Interferon gamma; Medical personnel; Methods; Properties; Skin tests; Tuberculosis; France
• ISSN: 1745-6673; 1745-6673
• DOI: 10.1186/1745-6673-4-30

Introduction Using French cut-offs for the Tuberculin Skin Test (TST), results of the TST were compared with the results of an Interferon-[gamma] Release Assay (IGRA) in Healthcare Workers (HCW) after contact to AFB-positive TB patients. Methods Between May 2006 and May 2007, a total of 148 HCWs of the University Hospital in Nantes, France were tested simultaneously with IGRA und TST. A TST was considered to indicate recent latent TB infection (LTBI) if an increase of >10 mm or if TST [greater than or equal to] 15 mm for those with no previous TST result was observed. For those with a positive TST, chest X-ray was performed and preventive chemotherapy was offered. Results All HCWs were BCG-vaccinated. The IGRA was positive in 18.9% and TST [greater than or equal to] 10 mm was observed in 65.5%. A recent LTBI was believed to be highly probable in 30.4% following TST. Agreement between IGRA and TST was low (kappa 0.041). In 10 (16.7%) out of 60 HCWs who needed chest X-ray following TST the IGRA was positive. In 9 (20%) out of 45 HCWs to whom preventive chemotherapy was offered following TST the IGRA was positive. Of those considered TST-negative following the French guidelines, 20.5% were IGRA-positive. In a two-step strategy - positive TST verified by IGRA - 18 out of 28 (64.3%) IGRA-positive HCWs would not have been detected using French guidelines for TST interpretation. Conclusion The introduction of IGRA in contact tracings of BCG-vaccinated HCWs reduces X-rays and preventive chemotherapies. Increasing the cut-off for a positive TST does not seem to be helpful to overcome the effect of BCG vaccination on TST.