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A loop-mediated isothermal amplification test for yaws: a multi-country diagnostic accuracy evaluation

Abstract

Background: To meet the WHO target of eradicating yaws by 2030, highly sensitive and specific diagnostic tools are needed. A multiplex Treponema pallidumHaemophilus ducreyi loop-mediated isothermal amplification (TPHD-LAMP) test holds promise as a near-patient diagnostic tool for yaws and H ducreyi. We conducted a prospective evaluation in Cameroon, Côte d’Ivoire, Ghana, and the Republic of the Congo to determine the diagnostic accuracy of the TPHD-LAMP test, as well as to assess its acceptability, feasibility, and cost.

Methods: Active case searching within schools and communities was used to locate participants with clinically suspicious laws-like lesions. Individuals with serologically confirmed active yaws provided paired lesion swabs between March, 2021, and April, 2023. For each participant, one swab was tested with the TPHD-LAMP at a local district laboratory and the other with reference quantitative PCR (qPCR) tests conducted at national reference laboratories. The primary outcome was TPHD-LAMP test sensitivity and specificity compared with qPCR. Laboratory technicians were interviewed using a multiple-choice survey to gauge acceptability and feasibility of the TPHD-LAMP test. Costs of each test were calculated.

Findings: Of 3085 individuals with at least one suspected yaws lesion, 531 (17%) were serologically confirmed. We enrolled 493 participants with seropositive yaws and a further 32 with negative serology. The sensitivity of the TPHD-LAMP test for detecting T pallidum was 63% (95% CI 56–70) and the specificity was 66% (95% CI 61–71). Sensitivity and specificity for T pallidum improved to 73% (63–82; p=0·0065) and 75% (68–80; p=0·0003), respectively, in H ducreyi-negative samples. Interviews highlighted challenges in user-friendliness and practicality of the TPHD-LAMP test. The cost of the test per sample was one third of that of qPCR, although the TPHD-LAMP test entailed higher costs to establish the assay.

Interpretation: This was the first multi-country diagnostic evaluation of a molecular test for yaws. The TPHD-LAMP testing, in its current form, falls short of the WHO target product profile criteria for yaws diagnostics. These findings highlight the importance of assessing new diagnostics in real-world conditions to ensure their suitability for programmatic use.

More information

Type
Journal Article
Author
Handley BL
Gonzalez-Beiras C
Tchatchouang S
Hugues KA
Basing LA
Sylla A
Kouamé-Sina MS
Amanor I
Ndzomo P
Aloumba A
Bakheit M
Müller C
Borst N
Landmann E
Gmoser H
Härpfer T
Becherer L
Lüert S
Frischmann S
Burl S
Tabah EN
Crucitti T
Kouadio AT
Arhinful DK
Awondo P
Kakou SN
Eyangoh S
Addo KK
Knauf S
Mitjà O
Harding-Esch EM
Marks M