Assessment of Petroff method modified with saline solution for the diagnosis of mycobacteria in Bact/Alert 3D system

Abstract

Introduction: There are different decontamination methods of pulmonary samples for the diagnosis of mycobacteria. The National Program for the Control of Tuberculosis recommends Petroff method modified with saline solution; but there are not documented evidences that endorse it.

Objective: Assess Petroff method modified with saline solution for the diagnosis of mycobacteria in Bact / Alert 3D system.

Methods: An observational analytic study of diagnostic tests was conducted; there were used 100 pulmonary samples received in the National Laboratory of References and Researches of Tuberculosis, Leprosy and Mycobacteria of ´´Pedro Kourí´´ Institute, from April 2016 to January 2017. The sample was divided in 3 aliquots and those were decontaminated using 3 methods; then, they were inoculated in the solid and liquid culture means. Cultures´ results were compared according to: growth’s detection time, contamination rate, % of positivity; in addition, performance indicators were calculated.

Results: When comparing Petroff method modified with saline solution with Petroff method modified with phosphate solution in Löwenstein Jensen, the growth’s detection time, the % of positivity and the rate of contamination behaved similarly, and sensitivity (93,75%), concordance (96,47%) and Youden´s index (0,91) were high. When the Petroff method modified with saline solution was compared with N-Acetil-L- Cisteina, the variables did not show significative differences and the behaviour indicators were over 93% for the solid and liquid mean.

Conclusions: The results endorse the continuity of the use of Petroff method modified with saline solution as a decontamination method of pulmonary samples in the network of Cuban laboratories and as alternative to the pre-treatment of the samples for the liquid mean (Bact/Alert 3D); it also constitutes a support for the National Program for the Control of Tuberculosis.