New simple decontamination method improves microscopic detection and culture of mycobacteria in clinical practice
Nora Morcillo1, Belén Imperiale1, Juan Carlos Palomino2
1Reference Laboratory of Tuberculosis Control Program of Buenos Aires Province, Dr. Cetrángolo Hospital, Buenos Aires, Argentina; 2Mycobacteriology Unit Institute of Tropical Medicine, Antwerp, Belgium
Abstract: This study was carried out at Dr. Cetrángolo Hospital, Buenos Aires, Argentina. The objective was to compare two digestion–decontamination procedures: the N-acetyl-Lcysteine–sodium citrate–NaOH (NALC-NaOH) and a combination of 7% NaCl plus NaOH, the hypertonic saline–sodium hydroxide (HS-SH) method, in detection and recovery of mycobacteria. Microscopy detection rates before and after concentration of specimens by both methods, were also compared. The study had two phases. Phase I: comparison of the gold standard NALC-NaOH and HS-SH on paired samples involving respiratory clinical specimens by means of receiver operating characteristic curve analysis. Phase II: blinded, randomized trial to assess the performance of HS-SH versus NALC-NaOH in clinical practice. Phase I: Positive microscopy rate was significantly increased in around 2.2% after concentration in comparison to that of specimens without concentration. The calculated sensitivity values for microscopy detection increased between 15.2% (HS-SH: 73.5%) to 16.7% (NALC-NaOH: 75.0%) over those without concentration (58.3%). Phase II: similar diagnostic rates by microscopy and cultures were obtained by either HS-SH or NALC-NaOH. The clinical performances were also very similar. These results and the low cost of the HS-SH procedure indicate the possibility of its implementation in clinical laboratories with high burden of tuberculosis cases and low resources.
Keywords: tuberculosis, diagnosis, clinical practice
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