Routine hospital use of a new commercial whole blood interferon-gamma assay for the diagnosis of tuberculosis infection.

Abstract

RATIONALE:

Interferon (IFN)-gamma blood tests may improve the current level of diagnostic accuracy for tuberculosis infection. The QuantiFERON-TB Gold (QFT-Gold) has been used in selected populations and shows higher specificity than the tuberculin skin test (TST).

OBJECTIVE:

To evaluate the QFT-Gold test in unselected patients and assess the level of agreement with the TST.

METHODS:

The test has been routinely performed on whole blood samples in our microbiology laboratory for 8 months. Demographic, clinical, and microbiological data have been collected and correlated to the QFT-Gold results.

MEASUREMENTS AND MAIN RESULTS:

Of 318 patients tested, 68 (21.4%) gave an indeterminate (low positive mitogen control) QFT-Gold result. Indeterminate results were significantly overrepresented in patients with a negative TST (28.9% vs. 6.6% in TST-positive patients; p < 0.0001, chi2 test) and were more frequent in patients receiving immunosuppressive therapies than in those who were not receiving such treatments (odds ratio, 3.35; 95% confidence interval, 1.84-6.08; p < 0.0001). After excluding indeterminate results, the concordance between QFT-Gold and TST was significantly lower in Bacille Calmette-Guérin-vaccinated individuals (41.5%) than in nonvaccinated individuals (80.3%) (p < 0.0001). In 11 patients with active tuberculosis (5 culture-confirmed), QFT-Gold provided more positive results than the TST (66.7% vs. 33.3%; p = 0.165).

CONCLUSIONS:

The QFT-Gold test is feasible in routine hospital use for the diagnosis of tuberculosis infection. As with the TST, immunosuppression may negatively affect the test's performance, with a significant rate of indeterminate results in the most vulnerable population.

• Authors: Giovanni Ferrara, Monica Losi, Marisa Meacci, Barbara Meccugni, Roberto Piro, Pietro Roversi, Barbara Maria Bergamini, Roberto D'Amico, Patrizia Marchegiano, Fabio Rumpianesi, Leonardo M Fabbri, Luca Richeldi
• Journal: American journal of respiratory and critical care medicine (Am J Respir Crit Care Med) Vol. 172 Issue 5 Pg. 631-5 (Sep 01 2005) ISSN: 1073-449X [Print] United States
• PMID: 15961696 (Publication Type: Journal Article)

Chemical References

• Interferon-gamma

Topics

• Adult
• Aged
• Diagnostic Tests, Routine (methods)
• Feasibility Studies
• Female
• Humans
• Immunoassay (methods)
• Interferon-gamma (blood)
• Male
• Middle Aged
• Skin Tests
• Tuberculosis (diagnosis)