Prospective comparison of the tuberculin skin test and 2 whole-blood interferon-gamma release assays in persons with suspected tuberculosis.
BACKGROUND
Interferon-gamma release assays (IGRAs) are attractive alternatives to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, the inability to definitively confirm the presence of most M. tuberculosis infections hampers assessment of IGRA accuracy. Although IGRAs are primarily indicated for the detection of latent tuberculosis infection, we sought to determine the sensitivity of the TST and 2 whole-blood IGRAs (QuantiFERON-TB assay [QFT] and QuantiFERON-TB Gold assay [QFT-G]) in situations in which infection is confirmed by recovery of M. tuberculosis by culture.


METHODS
We conducted a prospective, multicenter, cross-sectional comparison study in which 148 persons suspected to have tuberculosis were tested simultaneously with the TST, QFT, and QFT-G.


RESULTS
M. tuberculosis was cultured from samples from 69 (47%) of 148 persons suspected to have tuberculosis; the TST induration was > or = 5 mm for 51 (73.9%) of the 69 subjects (95% confidence interval [CI], 62.5%-82.8%). The QFT indicated tuberculosis infection for 48 (69.6%) of the 69 subjects (95% CI, 57.9%-79.2%) and was indeterminate for 7 (10.1%). The QFT-G yielded positive results for 46 (66.7%) of the 69 subjects (95% CI, 54.9%-76.7%) and indeterminate results for 9 subjects (13.0%). If subjects with indeterminate QFT-G results were excluded, 46 (76.7%) of 60 subjects (95% CI, 64.6%-85.6%) had positive TST results, and the same number of subjects had positive QFT-G results. HIV infection was associated with false-negative TST results but not with false-negative QFT-G results.


CONCLUSIONS
The TST, QFT, and QFT-G have similar sensitivity in persons with culture-confirmed infection. As with the TST, negative QFT and QFT-G results should not be used to exclude the diagnosis of tuberculosis in persons with suggestive signs or symptoms.
Mazurek
Gerald H
GH
Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. gym6@cdc.gov
Weis
Stephen E
SE
Moonan
Patrick K
PK
Daley
Charles L
CL
Bernardo
John
J
Lardizabal
Alfred A
AA
Reves
Randall R
RR
Toney
Sean R
SR
Daniels
Laura J
LJ
LoBue
Philip A
PA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004797:Enzyme-Linked Immunosorbent Assay; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology*; D014481:United States