Diagnosis of tuberculous pleuritis by nested polymerase chain reaction: a comparison of four different volumes of pleural fluid
Abstract number: p1111
Jaimchariyatam N., Kawkitinarong K., Naweewitphadung K., Udomsantisuk N., Tumwasorn S., Kulwichit W.
Tuberculous Pleuritis remains a major health problem worldwide. Laboratory diagnosis usually involves pleural fluid (PF) analysis and pleural tissue histopathology plus both specimens for culture and PCR. Diagnostic yields of PF PCR, however, is variable in different studies. Large volumes of specimens may give a better microbiologic diagnosis in certain conditions, as described in PF culture for M.tuberculosis and in PCR of vaginal discharge for C.trachomatis. Higher PF volumes may provide a better diagnostic yield of TB pleuritis.
A prospective observational study was conducted in patients with lymphocytic exudative pleural effusion at our university hospital from December 2004 to November 2005. Diagnosis of TB pleuritis is made by EITHER presence of pleural granuloma with or without acid fast bacilli plus a response to antituberculous therapy OR positive mycobacterial cultures of PF and/or pleural tissue. Patients with other final diagnoses served as a control group. Pleural fluids were divided in the laboratory into four different volumes of 1, 10, 50, and 150 ml before processing. The specimens were then centrifuged and the pellets produced were used for DNA extraction. Nested PCR using primers targeting IS6110 conserved among organisms in the TB complex group was performed. All standard PCR precautions were exercised. Presence of PCR inhibitors was tested in all specimens.
29 patients and 24 controls were enrolled (Table).
In the TB group, 6, 8, 12, and 6 of 29 specimens of 1, 10, 50, and 150 ml showed positive PCR results (sensitivity of 20.69%, 27.59%, 41.38%, and 20.69%, respectively). All control samples revealed negative results in all volumes used. The 150-ml group with positive PCR also gave positive results in all other volumes. The 50-ml group with positive PCR covered positive results in all other groups plus 4 additional cases. Processing of the 150-ml specimens occasionally produced large, sticky pellets potentially affecting the DNA quality. PCR inhibitors were detected in three specimens (from different patients) of 10, 50, and 150 ml each in the controls.
Higher volumes of pleural fluid increase a diagnostic sensitivity of tuberculous pleuritis by PCR to a certain extent. Too-large volumes, however, are unsuitable, probably due to presence of interfering proteins and other substances. Appropriate pleural fluid volumes should be assessed and verified in each laboratory.
|Session name:||XXIst ISTH Congress|
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