Evaluation of Combined LED-Fluorescence Microscopy and Bleach Sedimentation for Diagnosis of Tuberculosis at Peripheral Health Service LevelReport as inadecuate




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Background

Sputum microscopy is the only diagnostic for tuberculosis TB available at peripheral levels of health service in resource-poor countries. Its sensitivity is reduced in high HIV-prevalence settings. Sodium hypochlorite NaOCl specimen sedimentation prior microscopy and light-emitting diode LED-fluorescence microscopy FM can individually improve performance of microscopy. This study aimed to evaluate the performance of combined LED-FM and NaOCl sputum sedimentation for TB detection at peripheral level of health services.

Methods

A prospective study was conducted in an urban health clinic in Nairobi, Kenya. Three sputum specimens were collected over 2 days from consecutive TB suspects. Smears were prepared and stained with auramine O and Ziehl-Neelsen ZN methods. Bleach 3.5% was added to the remaining specimen before overnight sedimentation at room temperature. Auramine O staining was performed on smears of sediment. A 4th specimen was collected for TB culture. Auramine smears were read under the same microscope as used for ZN smears, but equipped with the LED FluoLED™ fluorescence illuminator.

Results

497 patients were included, and 1394 specimens collected. The yield of positive specimen was significantly increased after NaOCl sedimentation 24.9% compared to direct LED-FM 20.6% and direct ZN 20.3%. In detecting smear-positive patients, sensitivity was 78.5% for LED-FM after NaOCl sedimentation compared to 73.2% and 72.0% for direct LED-FM P = 0.06 and direct ZN P = 0.06, respectively. Specificity was 87.8% for LED-FM after NaOCl sedimentation compared to 96.7% and 95.9% for direct LED-FM P<0.01 and direct ZN P<0.01, respectively. Inter-reading agreement kappa = 0.7 and technicians- acceptability were good.

Conclusion

NaOCl sedimentation did not improve the performance of LED-FM in the diagnosis of pulmonary TB at peripheral health service level.



Author: Maryline Bonnet , Laramie Gagnidze, Philippe J. Guerin, Laurence Bonte, Andrew Ramsay, Willie Githui, Francis Varaine

Source: http://plos.srce.hr/



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