Sputum conversion at the end of 8 weeks among category 1 tuberculosis patients: How reliable are the peripheral laboratory results?

ObjectiveTo assess the quality of week 8 sputum smear AFB microscopy performed by peripheral TB laboratories in Nigeria.MethodA cross-sectional review was performed of all week 8 tuberculosis sputum smear slides reported for the first quarter of 2009 by peripheral laboratories in five States of Nigeria. Each slide was reviewed by two independent external slide readers as external quality check and also crosschecked with fluorescent microscopy.ResultsIn Akwa Ibom, Anambra, Enugu, Kogi and Ogun States, a total of 415, 315, 231, 206 and 428 week 8 slides respectively were studied (a grand total of 1595 slides studied). The wide range of conversion rates between the different States as reported by peripheral labs (83.8% in Anambra State to 98.1% in Kogi State) was also observed by the external quality check (68.4% in Kogi State to 88.0% in Akwa Ibom State). In all the States, the studied sputum conversion rates reported by the peripheral labs were significantly higher than values obtained from external quality check and fluorescent microscopy (P = 0.000).Conclusion/recommendationThere is a wide range of sputum conversion rates between States, but the conversion rate in each State is significantly higher than those of external quality check possibly indicating many false negative reports by peripheral labs. It is recommended that training and re-training of laboratory persons be continued. Internal and external quality checks should also continue to be practiced in the national TB program.