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. 2022 Apr 4;2(4):e0000116.
doi: 10.1371/journal.pgph.0000116. eCollection 2022.

Pooling sputum for Xpert MTB/RIF and Xpert Ultra testing during the Covid-19 pandemic in Lao People's Democratic Republic

Vibol Iem  1   2 , Phonenaly Chittamany  1 , Sakhone Suthepmany  1 , Souvimone Siphanthong  1 , Silaphet Somphavong  3 , Konstantina Kontogianni  2 , James Dodd  2 , Jahangir Akber Mahmud Khan  4 , Jose Dominguez  5 , Tom Wingfield  2   6 , Jacob Creswell  7 , Luis Eduardo Cuevas  2
Affiliations

Pooling sputum for Xpert MTB/RIF and Xpert Ultra testing during the Covid-19 pandemic in Lao People's Democratic Republic

Vibol Iem et al. PLOS Glob Public Health. .

Abstract

The global Covid-19 pandemic has limited access to molecular TB diagnostics and National Programmes are struggling to maintain essential services. The pooling method (testing several samples together) could reduce the number of cartridges and staff time needed for TB diagnosis but has not been tested within the pandemic. We conducted two independent cross-sectional surveys. Pools composed of four sputum samples were tested using either Xpert-MTB/RIF or Xpert-Ultra. Pooled and individual results were compared to determine the level of agreement. Each survey included 840 participants and 210 pools. In the Xpert MTB/RIF survey, 77/81 (sensitivity 95.1%, 95%CI 87.8%-98.6%) pools containing ≥1 positive sample tested MTB-positive and 4/81 (4.9%, 95%CI 1.4%-12.2%) tested MTB-negative. All 129/129 pools containing MTB-negative samples tested MTB-negative (specificity 100%, 95%CI 97.2%-100%), with 98.1% agreement (Kappa: 0.959). In the Xpert-Ultra survey, 70/70 (sensitivity 100%, 95%CI 94.9%-100%) pools containing ≥ 1 MTB-positive sample tested MTB-positive and 140/140 (specificity 100%, 95%CI 97.4%-100%) pools containing only MTB-negative samples tested MTB-negative, with 100% agreement (Kappa: 1). Pooled testing with Xpert-MTB/RIF and Xpert-Ultra saved 38.3% and 41.7% (322/840 and 350/840, respectively) in cartridge costs alone. The pooling method with Xpert-MTB/RIF and Xpert-Ultra has similar performance to individual testing and can reduce the number of cartridges needed. These efficiencies can facilitate maintenance of stocks and sustain essential services as countries face difficulties for laboratory procurement during the pandemic and will provide cost and time savings post-pandemic.

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Conflict of interest statement

The authors have no conflicts of interest to declare.

Figures

Fig 1
Fig 1. Flow diagram of the sputum processing.
Fig 2
Fig 2
Correlation of individual and pooled (A) Xpert MTB/RIF and (B) Ultra grades (positive pools only include those with one individual Xpert MTB-positive sample).
See this image and copyright information in PMC

References

    1. World Health Organization. Global Tuberculosis Report. 2019.
    1. Sismanidis C, Glaziou P, Bloss E, Hest R, Fatima R, Nguyen, et al.., editors. Understanding and addressing the tuberculosis case detection gap: national inventory studies to improve estimates of incidence and strengthen surveillance 2016. doi: 10.1016/S1473-3099(16)30132-3 - DOI - PubMed
    1. Uplekar M, Weil D, Lonnroth K, Jaramillo E, Lienhardt C, Dias HM, et al.. WHO’s new end TB strategy. Lancet. 2015;385(9979):1799–801. Epub 2015/03/31. doi: 10.1016/S0140-6736(15)60570-0 . - DOI - PubMed
    1. World Health Organization. Xpert MTB/RIF Implementation Manual: Technical and Operational ’How-To’; Practical Considerations. Xpert MTB/RIF Implementation Manual: Technical and Operational ’How-To’; Practical Considerations. WHO Guidelines Approved by the Guidelines Review Committee. Geneva: 2014. - PubMed
    1. World Health Organization. WHO meeting report of a technical expert consultation: non-inferiority analysis of Xpert MTF/RIF Ultra compared to Xpert MTB/RIF. 2017.

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