Pooled testing of sputum with Xpert MTB/RIF and Xpert Ultra during tuberculosis active case finding campaigns in Lao People's Democratic Republic. Issue 2 (14th February 2022)

• Record Type: Journal Article
• Authors: Iem, Vibol; Chittamany, Phonenaly; Suthepmany, Sakhone; Siphanthong, Souvimone; Siphanthong, Phitsada; Somphavong, Silaphet; Kontogianni, Konstantina; Dodd, James; Khan, Jahangir AM; Dominguez, Jose; Wingfield, Tom; Creswell, Jacob; Cuevas, Luis E
• Is Part Of: BMJ global health. Volume 7:Issue 2(2022)
• Publication Date: 2022-02-14
• Subjects: Xpert MTB/RIF -- Xpert Ultra -- pooling -- pooled testing -- active case finding; World health -- Periodicals; 362.105
• DOI: 10.1136/bmjgh-2021-007592
• Languages: English
• ISSNs: 2059-7908

Abstract

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.