Usefulness of the mycobacterium tuberculosis direct assay in early diagnosis of extrapulmonary TB

The aim of this study was to evaluate the in situ detection of living mycobacterium TB rRNA by the mycobacterium TB direct assay (MTD) and its clinical significance in the early diagnosis of extrapulmonary TB. Eighty-six patients were recruited from the Shanghai Public Health Clinical Center from June to November in 2010, having been diagnosed with extrapulmonary TB, including tuberculous peritonitis (n=22), lymphatic TB (n=21), tuberculous meningitis (n=15), HIV-associated TB (n=13), nephroTB (n=9), spinal TB (n=2), cutaneous TB (n=13), parotid TB (n=1), chest wall TB (n=1), intestinal TB (n=1). One hundred and five extrapulmonary specimens, including CSF, puncture fluid, drainage, pleural fluid, urine, secretion, ascites, lymphatic tissue and marrow were collected from the patients. The samples were examined using acid-fast stain, solid culture, liquid culture and MTD in parallel. In MTD, the target segments of MTB rRNA in either cultures or clinical specimens were amplified prior to being qualitatively detected with the hybridization protection assay (HPA). The sensitivities of MTD and acid-fast staining in liquid and solid cultures were 48.6%, 41.9%, 20.0% and 14.3%, respectively. MTD sensitivity was higher than that of the others and its specificity was 100%. We concluded that MTD rRNA detection is an effective, rapid, convenient, sensitive and reliable method for the early diagnosis of extrapulmonary TB