Pooled Sputum for Xpert MTB/RIF Testing: A Cost Effectiveness Diagnostic Tool in Mwanza, Tanzania

Abstract Background : Tuberculosis (TB) is a global public health problem, with the highest burden occurring in low-income countries, wherein the use of more sensitive diagnostics, such as Xpert MTB/RIF (GeneXpert), is still limited by costs. Testing of pooled samples from various individuals has been thought and thus investigated as a cost saving strategy to diagnose some diseases including TB. Then in cases where a pool is positive, retesting of the individual samples in that pool is done to identify the positive sample. We assessed the utility of a pooled testing strategy to optimize the affordability of GeneXpert for the diagnosis of TB Mwanza Tanzania. Methods: Remainder of samples from presumptive TB patients submitted for routine TB diagnosis were used for pooled samples (5 per pool) testing. The agreement of the results between individual sample testing against pooled samples testing and cost-effectiveness were assessed. Results: A total of 250 individual routinely submitted samples for TB diagnosis were tested using the established protocols. The median age of study participants was 35 [IQR 27 – 40] years and 143 (57.2%) were males. Of the 250 samples, 28 (11.2%) were detected to have MTB whereas 222 (88.8%) samples, were negative. Of the 50 sputum pools made, MTB were detected in 17 (34.0%) pools. Following retesting of these 17 positive pools, all 28 (100%) individual MTB samples were detected with the overall agreement being 100% (With the sensitivity of 100% and specificity of 100%). The number of individual MTB positive ranged from 1 to 3 per pool. Using pooling of sputum samples, the technique saved 115 (46.0%) of the cartridges in running 250 samples. This is equivalent to saving US$ 1147.7. Conclusion: The pooled sputum testing strategy reduced cartridge costs by 46.0%. The use of the pooled testing strategy reduces costs and has the potential to increase the affordability of GeneXpert testing in countries with limited resources. Pooled sputum for Xpert MTB/RIF can be used as an affordable diagnostic and/or screening tool in resource limited settings, such as Tanzania.