Impact of Randomized Blinded Rechecking program on the performance of the AFB Microscopy Laboratory Network in Uganda: A decadal retrospective study

Background: 

Classical smear microscopy has remained the first diagnostic test for most presumptive TB patients and the only susceptible TB treatment monitoring tool in Uganda. The country currently has over 1,600 microscopy TB testing units. Since AFB microscopy’s yield highly depends on the staining technique and reading ability of the microscopist, the TB control program set up a Randomized Blinded Rechecking (RBRC) program in 2008 to monitor the testing performance of laboratories to continuously improve the reliability and efficiency of results. This is the first study to determine its effectiveness and impact on the performance of the participating laboratories. 

Methods: 

This was a retrospective cross-sectional study based on a record review of the RBRC's annual results compilations between January 2008 and December 2017. 

Results: 

Between January 2008 and December 2017, a total of 265,523 smears were re-checked by the RBRC program. The number of enrolled laboratories in the RBRC program rose from 660 in 2008 to 1,406 in 2017. There was a statistically significant reduction in errors. False positive errors decreased from 12.8% in 2008 to 7.6% in 2017; high false positive errors decreased from 10% in 2008 to 6.3% in 2017; false negative errors decreased from 2.9% in 2008 to 0.7% in 2017; high false negative errors decreased from 2.1% in 2008 to 0.5% in 2017; and quantification errors decreased from 6.0% in 2008 to 1.8% in 2017. Laboratories with more than one High False Positive error decreased from 12% in 2008 to 4% in 2017, while those with more than one False Negative error decreased from 12% in 2008 to 3% in 2017. Lastly, the country’s sensitivity to smear microscopy, when compared to the re-checking controller, increased from 93% in 2008 to 97% in 2017. 

Conclusions: 

The study reveals an overall significant error reduction and an improved sensitivity of smear microscopy upon continuous implementation of the RBRC program in an AFB microscopy TB laboratory network. Implementation of a RBRC program is crucial and essential to maintaining a reliable laboratory service that can facilitate accurate diagnosis and offset the disadvantages of using smear microscopy