ORIGINAL: Assessment of Rifampicin Indeterminate Results among Adult Patients attending a Tertiary Tuberculosis Treatment Center in Port Harcourt Rivers State using Shewhart control Charts: Implications for patients and Tuberculosis Control Programs

West Afr J Med. 2024 June; 41(6): 682–690 PMID: 39340811

Abstract

Background: Antimicrobial resistance is a growing global public health concern, and multidrug-resistant Tuberculosis is responsible for roughly one-quarter of all antimicrobial-resistant infection-related deaths worldwide. GeneXpert is a rapid, automated molecular test that detects multi-drug-resistant Tuberculosis using Rifampicin as a predictor. The World Health Organization (WHO) in 2010 recommended GeneXpert for national tuberculosis programs in developing countries; however, it has limitations. Indeterminate results for Mycobacterium tuberculosis indicate that the test could not determine whether the bacteria were resistant to Rifampicin. This study used the Shewhart Control Chart, which has action limits, to investigate the causes of indeterminate results.

Methods: GeneXpert indeterminate results obtained between January and December 2019 in a tertiary hospital in a low and middle-income country were plotted. The control limits on the Shewhart chart are central, upper, and lower. Points above the upper control limit and successive points occurring in one zone were used to determine whether or not the process was under control.

Result: The resultant p-chart showed five points that were within the control limit, two points above the upper control limit, and five points consecutively in one zone on the plot. The former was characteristic of a stable process, while the latter was indicative of a special course variation respectively. The majority of the laboratory findings indicated an out-of-control signal.

Conclusions: GeneXpert indeterminate results impact patient management by preventing accurate diagnosis and delaying the start of anti-tuberculosis medication. Machine malfunctions, low bacterial load, poor-quality samples, operator errors, or faulty laboratory materials could all be to blame. Regular equipment checks by laboratory personnel, program sponsors, or leadership will be highly beneficial in achieving the desired results and initiating appropriate treatment. A large sample size or a multicenter study, could provide more data and yield more robust findings about nonconforming laboratory processes in diagnosing Rifampicin resistance.