Comparison of 2 interferon-gamma assays and Roche Cobas Amplicor Mycobacterium tuberculosis assay for rapid diagnosis of tuberculosis among patients with suspected tuberculosis in Taiwan.
OBJECTIVE
Two commercial interferon-gamma (IFN-gamma) assays, which are commonly used for diagnosing latent tuberculosis (TB), are also useful for diagnosis of active TB. In this study, the IFN-gamma assays and polymerase chain reaction (PCR) for diagnosis of TB were compared.


METHODS
A prospective comparison of the performance of 2 commercial IFN-gamma assays - QuantiFERON-TB Gold (QFT-G) and T-SPOT.TB (T SPOT) - and PCR using the Roche Cobas Amplicor Mycobacterium tuberculosis (RCA-TB) assay for the rapid diagnosis of TB was conducted from January 2007 to December 2007 at a university-affiliated hospital in Taiwan.


RESULTS
Of 187 patients enrolled in the study, results from both T SPOT and QFT-G were available for 154, including 109 patients with active TB and 45 with no TB. The sensitivity of T SPOT (89.0%) was higher than that of QFT-G (71.4%). RCA-TB had the highest sensitivity (90.2%) and specificity (100%), but was usually performed in patients with positive acid-fast bacilli smear test. In patients with extrapulmonary TB, T SPOT had a high diagnostic value (sensitivity, 81.3%). A significant discordance between the 2 IFN-gamma assays was also noted. IFN-gamma assays provided a more rapid diagnosis for tuberculosis than the conventional culture method (mean +/- standard deviation, 8.23 +/- 12.86 days; p < 0.001).


CONCLUSIONS
Use of IFN-gamma may shorten the time to diagnosis of TB, especially for smear-negative patients and those with extrapulmonary disease.
Chou
Chien-Hong
CH
Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, Yun-Lin, Taiwan.
Hsu
Hsiao-Leng
HL
Lee
Li-Na
LN
Hsueh
Po-Ren
PR
Luh
Kwen-Tay
KT
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013624:Taiwan; D014376:Tuberculosis / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
D007371:Interferon-gamma