Diagnostic values of peripheral blood T-cell spot of tuberculosis assay (T-SPOT.TB) and magnetic resonance imaging for osteoarticular tuberculosis: a case-control study

Abstract

Objective: Early diagnosis of osteoarticular tuberculosis helps improve patients' outcomes, but little is known about the accuracy of noninvasive diagnostic methods. This case-control study aimed to assess the diagnostic value of peripheral blood T-cell spot of tuberculosis assay (T-SPOT.TB) and magnetic resonance imaging (MRI).

Methods: Patients suspected with osteoarticular tuberculosis were retrospectively included and diagnosed according to the composite reference standard. T-SPOT.TB was used to detect the number of cells secreting Interferon gamma. Diagnostic performance of T-SPOT.TB and MRI alone and combined were evaluated.

Results: Among the suspected patients, 92 had osteoarticular tuberculosis and 137 non- osteoarticular tuberculosis. T-SPOT.TB assay alone had a higher sensitivity (0.73 vs. 0.60) but a lower specificity (0.69 vs. 0.91 P>0.05) in diagnosing osteoarticular tuberculosis. Combined serial test showed a sensitivity and specificity 0.47, 0.97, respectively, whereas combined parallel test showed a sensitivity and specificity of 0.86, 0.65, respectively. Specificity was higher in the combined serial test than in the T-SPOT.TB assay (P=0.007) or MRI alone (P < 0.001). Furthermore, sensitivity was higher in the combined parallel test than in the T-SPOT.TB assay (P < 0.001) or MRI alone (P < 0.001).

Conclusions: Combined blood T-cell spot of tuberculosis assay and osteoarticular MRI have higher sensitivity and specificity for noninvasive osteoarticular tuberculosis diagnosis, compared with either method alone.

Keywords: diagnostic accuracy; magnetic resonance imaging; osteoarticular tuberculosis; peripheral blood T-cell spot of tuberculosis assay.

Figure 1

Study flowchart.

Figure 2

Representative examples of T-SPOT.TB assay in non-OTB and OTB patients. This figure shows representative results of the T-SPOT.TB assay from two patients. Figure 2-OTB shows a positive result from an OTB patient. Figure 2-Non-OTB shows a negative result from a non-OTB patient.

Figure 3

Representative examples of MRI in OTB patients. (A, B) Thoracic spine tuberculosis: showing destruction of vertebral and paravertebral abscess. (C, D) Lumbar spine tuberculosis: showing destruction of vertebral and psoas abscess. (E, F) Right shoulder tuberculosis: showing worm like destruction of the right humeral head with effusion in the articular cavity. (G, H) Left hip joint tuberculosis: showing left hip joint synovitis and synovial fluid.