Study results confirm higher sensitivity of T-SPOT.TB in immunosuppressed patient groups

Oxford Immunotec Ltd, the T cell measurement company, has today announced the outcome of a recent study completed by a group in Milan demonstrating the sensitivity of T-SPOT™.TB in immunosuppressed patients.

The results, detailed in published correspondence in the American Journal of Respiratory and Critical Care Medicine confirm previously published findings in this patient group, which show that T-SPOT.TB is more sensitive than other available tests for TB diagnosis.

The authors draw comparison between the results of their study in 500 patients referred to the Lombardia Centre for Tuberculosis Control in Milan and earlier work published by Ferrara et al in the same journal last year.

In the Lombardia study the sensitivity of T-SPOT.TB was found to be 95.3% compared to 87% for the traditional Tuberculin Skin Test (‘TST’). The authors compared the 95.3% sensitivity reported for T-SPOT.TB and the earlier result reported by Ferrara et al of 66.7% sensitivity for QuantiFERON-TB Gold (QFN-Gold) an alternative blood test for diagnosis of TB. They also noted that the higher sensitivity of T-SPOT.TB appears to be a consistently emerging observation as further studies on the tests continue to be published.

The authors also commented on the difference in indeterminate rates (i.e. a failure to get any result when a test is performed). Ferrara et al reported indeterminate results with QFN-Gold at 23%, related in particular to the extent of immunosuppression in the patient groups. The authors compared this to the results achieved by T-SPOT.TB in a group of 170 immunosuppressed patients included within their study. In this, often severely immunosuppressed sub-population the indeterminate rate for T-SPOT.TB was only 4.7%.

These findings led the authors to conclude that T-SPOT.TB showed higher sensitivity than the TST. They also note that QFN-Gold showed a much higher proportion of indeterminate results than T-SPOT.TB in these immunosuppressed groups.

Commenting on the reported findings, Peter Wrighton-Smith, Chief Executive Officer of Oxford Immunotec said “We are delighted at how well the T-SPOT.TB test performed in the Lombardia study. The conclusions drawn by the Milan group reinforce the increased level of performance of T-SPOT.TB when compared to both the traditional TST and to the QuantiFERON product. This performance differential is particularly marked in immunosuppressed patient populations, and clearly supports our belief that T-SPOT.TB is the only blood test that performs consistently well in that patient population”.