Effect of 1.5% sodium hydroxide final concentration on recovery rate of Mycobacterial Species and decontamination of other Bacterial and Fungal contaminants on sputum

BACKGROUND: Digestion and decontamination of non-sterile clinical specimens such as sputum are an essential step in the isolation of mycobacteria. Masking of mycobacteria in Mycobacterial growth indicator tube (MGIT) 960 liquid culture system by fungi and bacteria other than mycobacteria is a major problem. OBJECTIVE: To assess the effect of 1.5% sodium hydroxide final concentration on recovery rate of mycobacterial species and decontamination of other bacterial and fungal contaminants from sputum sample. METHODOLOGY: Laboratory based cross sectional study with convenient sampling technique was carried out on subjects referred to the National Tuberculosis Reference Laboratory of Ethiopian Public Health Institute from November 2015 to February 2016. Single morning sputum was collected from each patient and analyzed. RESULTS: A total of 264 subjects were enrolled in the study. The mean age of participant was 31 (SD 20.14 – 41.42) years old. The majority (61%) were male. Increasing the final concentration of NaOH from 1% to 1.5% reduced the contamination rate from 22.4% to 6.8% (P