Diagnosis of active and latent tuberculosis (TB) remains a challenge; however, over the last few years, a new approach based on detecting Mycobacterium tuberculosis-specific T cells has shown much promise. In particular, there is substantial published evidence showing that the detection of ESAT-6- and CFP-10-specific T cells using the ex vivo enzyme-linked immunospot technique is a marked improvement over the existing tuberculin skin test. This technique, which detects gamma interferon-producing T cells, is now available as the commercial assay T SPOT-TB (Oxford Immunotec, Oxford, UK). In the present study, the usefulness of the T SPOT-TB test for diagnosis of TB in "real-world" clinical practice was investigated. Ninety patients of a southern German referral centre for TB with confirmed or suspected TB were randomly selected for this study. The results of the T SPOT-TB test were compared with the results of conventional diagnostic tools. The T SPOT-TB test detected 70 of 72 patients with pulmonary or extrapulmonary TB, indicating a sensitivity of 97.2% (95% confidence interval, 90.3-99.7). For 45 of these patients, tuberculin skin test (TST) results were also available. Only 40 (89%) of these 45 patients were positive in the TST compared to all 45 (100%) in the T SPOT-TB test (p=0.056). Among 12 of 90 patients for whom active TB disease was ruled out, the T SPOT-TB test was negative for 11 (92%), allowing the rapid exclusion of TB in patients suspected to have active TB disease. The T SPOT-TB test is a sensitive assay for detection of TB and represents a useful addition to the diagnostic algorithm available for detecting TB in low-incidence settings.

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The aim of the present study was to assess the cost-effectiveness of the new T-SPOT.TB assay versus the tuberculin skin test (TST) for screening contacts for latent tuberculosis (TB) infection in Switzerland.Health and economic outcomes of isoniazid treatment of 20-and 40-yr-old close contacts were compared in a Markov model over a 20-yr period following screening with TST only (at three cutoff values) and T-SPOT.TB alone or in combination with the TST.T-SPOT.TB-based treatment was cost-effective at J11,621 and J23,692 per life-year-gained (LYG) in the younger and older age group, respectively. No TST-based programmes were costeffective, except at a 15-mm cut-off in the younger group only, where the cost-effectiveness (J26,451?LYG -1 ) fell just below the willingness-to-pay threshold. Combination of the TST with T-SPOT.TB slightly reduced the total cost compared with the T-SPOT.TB alone by 4.4 and 5.0% in the younger and older groups respectively. The number of contacts treated to avoid one case of TB decreased from 50 (95% confidence interval 32-106) with the TST (10-mm cut-off) to 18 (95%CI 11-43) if T-SPOT.TB was used. Using T-SPOT.TB alone or in combination with the tuberculin skin test for screening of close contacts before latent tuberculosis infection treatment is highly cost-effective in reducing the disease burden of tuberculosis.KEYWORDS: Cost-effectiveness, interferon-c release assay, latent tuberculosis infection, latent tuberculosis infection treatment, tuberculosis S creening the contacts of patients with tuberculosis (TB) is recommended as a strategy to detect infected persons who may develop the disease at a later time. It has been demonstrated that preventive treatment, mainly with isoniazid, decreases the number of future cases of TB. This strategy is therefore recommended in countries with a low incidence rate of TB, in order to further decrease the burden of disease [1]. The effectiveness and cost-effectiveness of these programmes are strongly affected by the accuracy of identifying truly infected individuals who have a risk of developing future disease. Owing to the limited sensitivity and specificity of the tuberculin skin test (TST), it follows that the current cost-effectiveness of screening may be improved if more accurate tools are used for screening for latent tuberculosis infection (LTBI).Numerous studies screening recent contacts of infectious TB patients for LTBI using the new highly specific interferon-c release assays (IGRA) have recently been published [2][3][4][5][6][7], but no study has produced cost-effectiveness data. In two papers [8,9] the way in which IGRA can be used for cost-saving in initial screening has been discussed. However, the long-term economic consequences and healthcare outcomes of this new approach for detecting Mycobacterium tuberculosis infection were not examined in the context of subsequent treatment of LTBI in comparison with existing programmes based upon the TST.As intervention options in all therapeutic areas grow, government and third-party...

Interferon-c release assays for the diagnosis of tuberculosis (TB) Of a total of 1,429 tests, 49 (3.4%) were indeterminate. ITRs were significantly associated with old age (.75 versus 5-75 yrs; odds ratio (OR) 7.97, 95% confidence interval (CI) 3.968-15.438) and the season during which samples were transported (autumn and winter versus spring and summer; OR 3.47, 95% CI 1.753-7.514). The incidence of ITR was 302 (2.0%) among TB contacts, 75 (1.6%) among immigrants, 156 (3.0%) in TB suspects and 32 (3.0%) among immunosuppressed patients. Sex, young age and distance to the laboratory were not associated with the rate of ITR. Of the 13 tests with ITR that were repeated, 10 gave a clear positive or negative result.Indeterminate test results with T-SPOT TM .TB under routine conditions were infrequent and more common in individuals aged .75 yrs than in children and younger adults. The incidence of indeterminate test results was low and similar among healthy tuberculosis contacts, immigrants with a positive tuberculin skin test, tuberculosis suspects and the immunosuppressed. The conditions of transportation may influence the incidence of indeterminate test results.