Diagnostic usefulness of a T-cell-based assay for extrapulmonary tuberculosis in immunocompromised patients.
BACKGROUND
The low reactivity of the tuberculin skin test limits its clinical use in immunocompromised patients with extrapulmonary tuberculosis. A recently developed T-cell-based assay for diagnosing tuberculosis infection gave promising results. However, there were few data on the usefulness of this assay for diagnosing extrapulmonary tuberculosis in immunocompromised patients.


METHODS
All adult patients with suspected extrapulmonary tuberculosis were prospectively enrolled at 2 university-affiliated hospitals over an 18-month period. In addition to the conventional tests for diagnosing extrapulmonary tuberculosis, enzyme-linked immunospot (ELISPOT) assay for the interferon-gamma-producing T-cell response to early secretory antigenic target-6 and culture filtrate protein-10 was performed. The final diagnoses in patients with suspected extrapulmonary tuberculosis were classified by clinical category.


RESULTS
There were 179 patients with suspected extrapulmonary tuberculosis enrolled: 59 (33%) were classified as immunocompromised. Of the 179 patients, 75 (42%) were classified as extrapulmonary tuberculosis, including 56 confirmed tuberculosis plus 19 probable tuberculosis, and 97 (54%) were classified as not tuberculosis. The remaining 7 (4%) had possible tuberculosis and were excluded from the final analysis. The tuberculin skin test (induration size >or=10 mm) was less sensitive in immunocompromised patients (38%; 95% confidence interval [CI], 19%-59%) than in immunocompetent patients (69%; 95% CI, 54%-81%, P=.01). In contrast, the ELISPOT assay retained a high sensitivity: (88%; 95% CI, 68%-97%) in immunocompromised patients compared with 96% (95% CI, 87%-100%) in immunocompetent patients (P=.32).


CONCLUSIONS
The immunosuppressive condition does not affect the diagnostic sensitivity of the ELISPOT assay for extrapulmonary tuberculosis.
Kim
Sung-Han
SH
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
Song
Kyoung-Ho
KH
Choi
Su-Jin
SJ
Kim
Hong-Bin
HB
Kim
Nam-Joong
NJ
Oh
Myoung-don
MD
Choe
Kang-Won
KW
D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology; D001426:Bacterial Proteins / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D016867:Immunocompromised Host; D007371:Interferon-gamma / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013601:T-Lymphocytes / Q000276:immunology*; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C525005:ESAT-6 antigen, Mycobacterium leprae; D007371:Interferon-gamma