Systematic Review of Pooling Sputum as an Efficient Method for Xpert MTB/RIF Tuberculosis Testing during the COVID-19 Pandemic

Abstract

GeneXpert-based testing with Xpert MTB/RIF or Ultra assays is essential for tuberculosis diagnosis. However, testing may be affected by cartridge and staff shortages. More efficient testing strategies could help, especially during the coronavirus disease pandemic. We searched the literature to systematically review whether GeneXpert-based testing of pooled sputum samples achieves sensitivity and specificity similar to testing individual samples; this method could potentially save time and preserve the limited supply of cartridges. From 6 publications, we found 2-sample pools using Xpert MTB/RIF had 87.5% and 96.0% sensitivity (average sensitivity 94%; 95% CI 89.0%-98.0%) (2 studies). Four-sample pools averaged 91% sensitivity with Xpert MTB/RIF (2 studies) and 98% with Ultra (2 studies); combining >4 samples resulted in lower sensitivity. Two studies reported that pooling achieved 99%-100% specificity and 27%-31% in cartridge savings. Our results show that pooling may improve efficiency of GeneXpert-based testing.

Keywords: COVID-19; SARS-CoV-2; TB; Xpert MTB/RIF testing; antimicrobial resistance; bacteria; coronavirus disease; diagnostics; mycobacteria; pandemic; pooling; severe acute respiratory syndrome coronavirus 2; systematic reviews; tuberculosis; tuberculosis and other mycobacteria; viruses.

Figure 1

Flow diagram of study selection for a systematic review of pooling sputum as an efficient method for Xpert MTB/RIF and Ultra (Cepheid, https://www.cepheid.com) testing for tuberculosis during the coronavirus disease pandemic.

Figure 2

Sensitivity and specificity for pooling sputum in the ratio of 1:2 (A) and pooling sputum in the ratio of 1:4 (B) in a systematic review of pooling sputum as an efficient method for Xpert MTB/RIF and Ultra testing (Cepheid, https://www.cepheid.com) for tuberculosis during the coronavirus disease pandemic.