Short communication: Impact of directly observed sputum collection on sputum culture contamination rates

G Muzanyi, M Angel, T Nakamate, S Ogwang, S Nyole

Abstract

TB sputum culture contamination is relatively common despite strong lab decontamination procedures. The sources of sputum contamination include: normal flora, level of oral hygiene, lab methodology and techniques of sputum collection. The techniques of sputum collection may include but not limited to specific instructions by health workers to patients about collecting sputum2, 3. Whether the patients understand and put the instructions in practice may not always be followed.

In previous studies done on site at the mulago TB project clinic, contamination rates have gone as high as 30%. In one study: impact of mouth rinsing on sputum culture contamination rates1, the contamination rates were reduced from as high as 22% to as low as 7% with the intervention of mouth rising.

It was then reported that patients sometimes carry sputum from home using unsterile containers which sputum is then transferred to the clinic containers without the knowledge of the clinic staff. The feeling was that this could be another source of contamination. It was hypothesized that by directly observing sputum collection, we can further reduce the sputum culture contamination rates.