Combined use of a TST and the T-SPOT®.TB assay for latent tuberculosis infection diagnosis before anti-TNF-α treatment.

BACKGROUND

Diagnosis of latent tuberculosis infection (LTBI) before anti-tumour-necrosis factor (anti-TNF) treatment is important. However, the tuberculin skin test (TST) has limitations, and the role of interferon-gamma release assays has not yet been determined.

OBJECTIVE

To evaluate the combined use of TST and the T-SPOT(®).TB (T-SPOT) assay prior to anti-TNF treatment.

METHODS

From July 2004 to March 2008, 281 patients were treated with anti-TNF agents. TST and T-SPOT were performed simultaneously at baseline. LTBI was defined as a positive TST of ≥10 mm induration or as a positive T-SPOT if TST was ≥5 mm but <10 mm. LTBI treatment was initiated, and patients were followed until August 2010.

RESULTS

Positivity rates for TST and T-SPOT were respectively 33.6% (94/280) and 69.1% (186/269). LTBI treatment was initiated in 35.9% (101/281) of the patients, and active TB developed in 2.1% (6/281). Among the six TB patients, three were TST-negative at baseline and received no LTBI treatment, whereas all four who underwent T-SPOT showed positive results at baseline.

CONCLUSION

In a TB-prevalent country, TST-defined LTBI diagnosis and treatment seem to be limited in preventing the development of TB before anti-TNF treatment. Further studies for T-SPOT alone or the combined use of TST and T-SPOT (either test positive strategy) for detecting LTBI are necessary.