Avalilação PREreview de Evaluation of the Clinical Performance of Two New Onchocerciasis Rapid Diagnostic Tests

Does the introduction explain the objective of the research presented in the preprint?

Yes. 

The introduction clearly states the objective of the research in the preprint, which is to determine whether two newly developed BA/GADx and DDTDc rapid diagnostic tests (RDTs) resulted in reliable clinical performance under field conditions in Ghana, eventually benefitting in elimination programs of onchocerciasis. 

The introduction provides background information on these two new tests, while comparing them against previous diagnostic references like the original SD Ov16 RDT and skin-snip qPCR. By addressing multiple limitations, the introduction recognizes the need for improved diagnostic tools to use in low-prevalence settings. 

The study objective appears at the end of the introduction with insufficient emphasis at the beginning. To enhance comprehensibility, it would be helpful to add testable hypotheses for future functional studies. It is also necessary to refer to studies that are recently published as some sources refer to works in 1993 or 2018. Methods are described in detail, but could be summarized briefly in introduction for clarity.

Are there any methodological issues or are the methods well-suited for this research?

Somewhat Appropriate with Relevant Techniques

The methods have some strengths that show it is generally well designed. One major strength is it has a large and adequate sample size (1700 participants) across various communities that vary in endemicity. There is a head-to-head comparison with the original SD Ov16 RDT. There is a use of multiple references like skin snip microscopy and specific types of qPCR when assessing the new RDTs, providing a comprehensive evaluation of diagnostic performance. By testing in whole blood and laboratory settings, it addresses point-of-care applicability. However, there are a few major and minor issues that are necessary to be addressed for improvement. 

Major Issues:

1. The SD Ov16 RDT is not a gold standard and may affect the sensitivity analyses through reference standard bias. 

2. There is a very low number of O-150 qPCR positive cases, limiting the ability to evaluate the specificity and alignment with WHO TPP performance targets. 

3. Adults were only considered when performing skin snip microscopy and qPCR, which may limit generalizability when comparing results across all ages.

4. Agreeability is reduced as evaluated RDTs detect exposure while qPCR and microscopy detect active infection, complicating direct comparison between the methods

Minor Issues:

1. Environmental conditions are not documented like temperature and humidity during field testing that could affect RDT performance.

2. Storage duration and conditions prior to laboratory testing of DBS may have affected antibody stability even if it was not assessed. 

3. Conducting the study only in Ghana may limit applying the new RDTs to other regions with various transmission dynamics or co-endemicities.  

Are the data presentations and collections well-suited to represent the data?

Highly suitable

The results are clearly stated and well aligned with the study’s objectives. Data collection methods are appropriate and robust for field diagnostic evaluations and collecting parallel specimens (plasma, DBS, skin snips, and whole blood) provided cross-method comparisons during data analysis. Results are clearly structured by sample matrix (whole blood vs. laboratory), test type, and reference standard. Presentation of sensitivities with confidence intervals, kappa statistics, and concordance values convey epidemiological trends and consistency across tests. Figures are also included to show infection prevalence by district and percentage positivity by age groups. However, there were a few major issues with the presentation that could be refined to improve interpretability of the results. Additional experiments may need to be performed to strengthen the contribution of the new RDTs.

Major Issues:

1. There is insufficient data to draw robust conclusions on the specificity and alignment of the new RDTs with WHO TPP performance thresholds. For instance, the results show that there are very low numbers of skin snip microscopy and O-150 qPCR positives, limiting specificity assessment.

2. Data rely heavily on the SD Ov16 RDT as a reference, and may need to be compared with other RDTs as relative performance assessments. 

3. There are some issues with the data presentation in Figure 1 and Figure 3. When presenting prevalence estimates from antibody-based RDTs and the original SD Ov16 RDT in Figure 1, it doesn’t emphasize that the results represent exposure to infection rather than active infection. Readers may misinterpret prevalence as active transmission, which is often the case in elimination settings. In Figure 3, there is an inconsistency when sensitivity is calculated against SD Ov16 serology as the preprint mentions that TPP characteristics are to be compared with the qPCR results. This means that TPP sensitivity targets are assessed against current infection, which doesn’t align when comparing with Ov16-based RDTs that detect exposure. 

Are the conclusions supported by the data?

Somewhat supported by the data 

This study provides critical real-world evidence on the performance of two new antibody-based RDTs for onchocerciasis. Both tests showed acceptable sensitivity, operational feasibility, and potential utility in field diagnostics for elimination programs. However, their reliance on antibody detection and limitations in assessing exposure from active infection shows that the new RDTs are not yet ready to be used for molecular diagnostics to progress future MDA cessation or elimination. 

Major Issues:

1. Conclusions about meeting TPP sensitivity targets are sometimes drawn from comparisons with original SD Ov16 RDT rather than qPCR as there was insufficient qPCR data, which undermines the validity of the claims.

2. There is insufficient data for the implied inferences that these new tests can inform elimination programs or current transmission. 

Would you recommend this preprint to others?

Yes, I would recommend it because of its high quality, despite having some major and minor issues. It is well-conducted and provides clinically relevant insights that could inform future advancements in onchocerciasis diagnostics and elimination. 

Does the paper maintain professional integrity and ethics?

Professional integrity and ethics are maintained.

• Ethical approval was obtained from the Institutional Review Board of the Noguchi Memorial Institute for Medical Research, University of Ghana. 

• Written informed consent was obtained from all adult participants. 

• Parental consent was obtained for all children who were participants. 

Competing interests

The author declares that they have no competing interests.

Use of Artificial Intelligence (AI)

The author declares that they did not use generative AI to come up with new ideas for their review.