Q: I am 30 years old and a suspected case of Sacroiliac joint tuberculosis. My IgG, IgM are within normal limits. I want to know the specific diagnostic tests for tuberculosis of the bone?

A:The common sites involved in bone TB are the large weight bearing bones or joints including the vertebrae, hip and knee. Destruction of the bones with deformity is a late sign of TB. Serology has a limited role in diagnosis of TB, due to poor sensitivity and specificity. Radio-nuclide bone scans may be helpful, but definitive diagnosis can only be made with aspiration of material/biopsy of the affected area (which may not be possible in all case), followed by microbiological investigations - AFB staining, AFB culture/sensitivity and/or nucleic acid amplification tests like PCR or geneprobe.