Diagnostic usefulness of a T-cell-based assay for osteoarticular tuberculosis.
BACKGROUND
Although diagnosing osteoarticular tuberculosis (TB) remains a challenge, a recently developed Mycobacterium tuberculosis-specific ELISPOT assay for diagnosing TB infection has shown promising results. We performed a prospective, blinded, observational study to compare its diagnostic usefulness with those of conventional tests in patients with suspected osteoarticular TB.


METHODS
All patients presenting at a tertiary hospital between April 2008 and September 2009 with suspected osteoarticular TB were enrolled. In addition to conventional tests for TB, we used ELISPOT assays to measure the IFN-gamma response to ESAT-6 and CFP-10 in T-cells in samples of peripheral blood mononuclear cells (PBMC). Patients with suspected osteoarticular TB were classified by diagnostic category.


RESULTS
Of the 65 patients with suspected osteoarticular TB, 5 (8%) were excluded due to inconclusive diagnoses. Of the remaining 60 patients, 23 (38%) were classified as having confirmed TB, 3 (5%) as having probable TB, 2 (3%) as having possible TB, and 32 (53%) as not having active TB. Five (8%) patients with probable or possible TB were excluded from the final analysis. Of the 23 patients with confirmed osteoarticular TB, 15 (65%) had TB spondylitis, 4 (17%) had TB arthritis, 2 (9%) had prosthetic joint infection, and 2 (9%) had extra-spinal TB. The sensitivities of the tuberculin skin test (> or =10 mm) and the ELISPOT assay for active osteoarticular TB were 80% (95% confidence interval [CI], 58%-92%) and 100% (95% CI, 85%-100%) (P = 0.04), respectively and their specificities were 68% (95% CI, 51%-81%) and 58% (95% CI, 41%-74%) (P = 0.60), respectively.


CONCLUSIONS
A negative ELISPOT assay using PBMC may be a useful test for excluding a diagnosis of active osteoarticular TB.
Cho
Oh-Hyun
OH
Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Pungnap-dong, Songpa-gu, Seoul 138-736, Republic of Korea.
Park
Su-Jin
SJ
Park
Ki-Ho
KH
Chong
Yong Pil
YP
Sung
Heungsup
H
Kim
Mi-Na
MN
Lee
Sang-Oh
SO
Choi
Sang-Ho
SH
Woo
Jun Hee
JH
Kim
Yang Soo
YS
Kim
Sung-Han
SH
D000328:Adult; D000368:Aged; D000942:Antigens, Bacterial / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry; D058501:Enzyme-Linked Immunospot Assay / Q000379:methods*; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D013601:T-Lymphocytes / Q000378:metabolism*; D014394:Tuberculosis, Osteoarticular / Q000097:blood / Q000175:diagnosis*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma