Pooled testing of sputum with Xpert MTB/RIF and Xpert Ultra during tuberculosis active case finding campaigns in Lao People’s Democratic Republic

Iem, Vibol, Chittamany, Phonenaly, Suthepmany, Sakhone, Siphanthong, Souvimone, Siphanthong, Phitsada, Somphavong, Silaphet, Kontogianni, Konstantina, Dodd, James, Khan, Jahangir AM, Dominguez, Jose, Wingfield, Tom ORCID: https://orcid.org/0000-0001-8433-6887, Creswell, Jacob and Cuevas, Luis ORCID: https://orcid.org/0000-0002-6581-0587 (2022) 'Pooled testing of sputum with Xpert MTB/RIF and Xpert Ultra during tuberculosis active case finding campaigns in Lao People’s Democratic Republic'. BMJ Global Health, Vol 7, Issue 2, e007592.

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Abstract

Introduction: Active case finding (ACF) of individuals with tuberculosis (TB) is a key intervention to find the 30% of people missed every year. However, ACF requires screening large numbers of individuals who have a low probability of positive results, typically <5%, which makes using the recommended molecular tests expensive.
Methods: We conducted two ACF surveys (in 2020 and 2021) in high TB burden areas of Lao PDR. Participants were screened for TB symptoms and received a chest X-ray. Sputum samples of four consecutive individuals were pooled and tested with Xpert Mycobacterium tuberculosis (MTB)/rifampicin (RIF) (Xpert-MTB/RIF) (2020) or Xpert-Ultra (2021). The agreement of the individual and pooled samples was compared and the reasons for discrepant results and potential cartridge savings were assessed.
Results: Each survey included 436 participants, which were tested in 109 pools. In the Xpert-MTB/RIF survey, 25 (sensitivity 89%, 95% CI 72.8% to 96.3%) of 28 pools containing MTB-positive samples tested positive and 81 pools containing only MTB-negative samples tested negative (specificity 100%, 95% CI 95.5% to 100%). In the Xpert-Ultra survey, all 32 (sensitivity 100%, 95% CI 89.3% to 100%) pools containing MTB-positive samples tested positive and all 77 (specificity 100%, 95% CI 95.3% to 100%) containing only MTB-negative samples tested negative. Pooling with Xpert-MTB/RIF and Xpert-Ultra saved 52% and 46% (227/436 and 199/436, respectively) of cartridge costs alone.
Conclusion: Testing single and pooled specimens had a high level of agreement, with complete concordance when using Xpert-Ultra. Pooling samples could generate significant cartridge savings during ACF campaigns.

Item Type:	Article
Subjects:	QY Clinical Pathology > Diagnostic Tests > QY 120 Sputum WF Respiratory System > Tuberculosis > WF 200 Tuberculosis (General) WF Respiratory System > Tuberculosis > WF 220 Diagnosis. Prognosis
Faculty: Department:	Clinical Sciences & International Health > Clinical Sciences Department Clinical Sciences & International Health > International Public Health Department
Digital Object Identifer (DOI):	https://doi.org/10.1136/bmjgh-2021-007592
SWORD Depositor:	JISC Pubrouter
Depositing User:	JISC Pubrouter
Date Deposited:	28 Mar 2022 11:35
Last Modified:	04 Oct 2023 12:45
URI:	https://archive.lstmed.ac.uk/id/eprint/19998

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