Sensitivity of human gamma interferon assay and tuberculin skin testing for detecting infection with Mycobacterium tuberculosis in patients with culture positive tuberculosis.
METHODS
Nine university-affiliated chest clinics in Australia.


OBJECTIVE
To evaluate the sensitivity of a whole blood human gamma-interferon assay (HGIA, QuantiFERON-TB) for specific T lymphocyte responses and Tuberculin skin testing (TST) for the detection of Mycobacterium tuberculosis infection in subjects with culture-proven M. tuberculosis disease (TBCP).


METHODS
Prospective testing of 129 patients with recent TBCP and 100 patients with non-tuberculosis lung disease (NTBLD).


RESULTS
Using a defined level of specific IFN-gamma production and TST 10mm as positive cut-offs, the sensitivity of HGIA was 81% compared to 89% for TST (p=0.06). When positive responses in both TST and HGIA were combined, 96% of TB patients were detected. For the NTBLD group, 43% of whom were born overseas, 73% were negative for both the HGIA and TST. Prior immunization with M. bovis (bacille Calmette-Guerin) (BCG) or the type of TB had no effect on the sensitivities of the assays. For those treated for <2 months, the sensitivities for both assays were 84%, but for those treated for >2 months the sensitivity of TST (90%) tended to be higher than for HGIA (81%) (p=0.07). The distribution of TST results in TB patients showed a broad peak between 10 and 25 mm, while the results in the HGIA were bimodal in both TB and NTBLD patients.


CONCLUSIONS
HGIA may prove an alternative to skin testing for detecting M. tuberculosis infection in certain settings.
Britton
W J
WJ
Centenary Institute of Cancer, Medicine and Cell Biology, Locked Bag No. 6, Newtown NSW 2042, Australia. wbritton@medicine.usyd.edu.au
Gilbert
G L
GL
Wheatley
J
J
Leslie
D
D
Rothel
J S
JS
Jones
S L
SL
Bradley
P
P
D000328:Adult; D000368:Aged; D000995:Antitubercular Agents / Q000008:administration & dosage; D001500:BCG Vaccine; D015415:Biomarkers / Q000097:blood; D003937:Diagnosis, Differential; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007371:Interferon-gamma / Q000097:blood*; D008171:Lung Diseases / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000188:drug therapy
D000995:Antitubercular Agents; D001500:BCG Vaccine; D015415:Biomarkers; D007371:Interferon-gamma