QuantiFERON-TB Gold and TST are both useful for latent TB screening in autoimmune diseases

¹ SOD Malattie Infettive e Tropicali, Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy
² Clinica Malattie Infettive, Dipartimento Area Critica Medico-Chirurgica, Università degli Studi di Firenze, Italy
³ UOC Epidemiologia Clinica, Istituto Nazionale di Malattie Infettive "Lazzaro Spallanzani", Roma, Italy
⁴ SOD Medicina Interna I Divisione di Reumatologia, Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy
⁵ SOD Medicina Interna I Divisione di Reumatologia, Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy; and Dipartimento di Medicina Interna, Università degli Studi di Firenze, Italy
⁶ Centro di Riferimento Regione Toscana per la Diagnostica dei Micobatteri, SOD Microbiologia e Virologia, Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy
⁷ Servizio di Reumatologia, Nuovo Ospedale San Giovanni di Dio, Firenze, Italy
⁸ SOD Malattie Infettive e Tropicali, Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy; and Clinica Malattie Infettive, Dipartimento Area Critica Medico-Chirurgica, Università degli Studi di Firenze, Italy

^* To whom correspondence should be addressed. E-mail: bartalesif{at}aou-careggi.toscana.it.

	Abstract

Screening for active tuberculosis (TB) and latent TB (LTBI) is mandatory prior to initiation of TNF inhibitors therapy. However, no agreement exists on the best strategy for detecting LTBI in this population.

The aim of this study was to analyze the performance of tuberculin skin test (TST) and QuantiFERON^®-TB Gold In Tube (QFT) on LTBI detection in subjects with immunomediated inflammatory diseases (IMID).

TST and QFT were prospectively performed in 398 consecutive IMID subjects, 310 (78%) on immunosuppressive therapy and only 16 (4%) Bacillus Calmette-Guérin (BCG)-vaccinated.

Indeterminate results to QFT were found in 5 (1.2%). Overall 74/393 subjects (19%) were TST+ and 52 (13%) QFT+. Concordance between TST and QFT results was good (87.7%) (kappa 0.55): 13 were QFT+/TST- and 35 QFT-/TST+. By multivariate analysis both tests were associated significantly with older age. Just TST was associated with BCG vaccination and radiological lesions of past TB. Use of immunosuppressive drugs differently modulated QFT or TST scoring.

Use of the QFT test, as a screening tool for LTBI among IMID subjects, is feasible. Until further data will elucidate discordant TST/QFT results, a strategy of simultaneous TST and QFT testing in a low prevalence BCG-vaccinated population, should maximize potentials of LTBI diagnosis.

Keywords:  Interferon- release assay, latent tuberculosis infection, rheumatic diseases, TNF inhibitors, tuberculin test

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