Diagnostic usefulness of a T-cell-based assay for osteoarticular tuberculosis

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.
The Journal of infection (Impact Factor: 4.02). 09/2010; 61(3):228-34. DOI: 10.1016/j.jinf.2010.06.015
Source: PubMed

ABSTRACT 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.
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.
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.
A negative ELISPOT assay using PBMC may be a useful test for excluding a diagnosis of active osteoarticular TB.

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