Diagnostic value of ELISPOT technique for osteoarticular tuberculosis

Osteoarticular tuberculosis (TB) is a common severe form of extrapulmonary tuberculosis. Early di- agnosis and treatment can decrease the deformity of spine and limbs and joint dysfunction.

We compared and evaluated two commercially available rapid test kits based on the ELISPOT assay for the diagnosis of osteoarticular disease.

The diagnostic sensitivity and specificity of the FS-SPOT assay (50.0% and 85.7%) were similar to those of the T-SPOT-TB assay (45.5% and 81.0%). When the two test wells in the T-SPOT-TB assay were both positive, the test wells in FS-SPOT assay were usually positive with the number of SFCs exceeding those in the negative control wells by more than 30. The sensitivities, specificities, PPV, NPV, and agreement of FS-SPOT assay results in 99 TB cases and 54 non-TB disease cases were 55.6%, 83.3%, 84.7%, 52.9%, and 66.0%, respectively. SFC counts from test wells in the TB group were significantly higher than those from the non-TB group (p < 0.001).

Higher numbers of SFCs in the ELISPOT assay suggest higher risk of active TB. ELISPOT may be a diagnostic aide for active osteoarticular TB.