MALDI-TOF MS for malaria vector surveillance: A cost-comparison analysis using a decision-tree approach

Jonathan Karisa; Cassidy Rist; Mercy Tuwei; Kelly Ominde; Brian Bartilol; Zedekiah Ondieki; Haron Musani; Caroline Wanjiku; Joseph Mwangangi; Charles Mbogo; Martin Rono; Philip Bejon; Marta Maia

doi:10.1371/journal.pone.0335764

Peer Review History

Original SubmissionJuly 15, 2025
3 Oct 2025 Decision Letter - Bersissa Kumsa, Editor Dear Dr. Karisa, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Nov 17 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. 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If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. 5. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: Dear Authors, The reviewers have completed their evaluation of your manuscript. I encourage you to revise and resubmit your work, ensuring that all reviewer comments are thoroughly addressed. Please incorporate the feedback carefully and provide a detailed, point-by-point response that clearly outlines every change made in response to the reviewers’ suggestions. In addition, kindly correct all typographical and grammatical errors, and ensure that the manuscript is prepared in full compliance with the journal’s formatting and submission guidelines. We look forward to receiving your revised submission. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available??> The PLOS Data policy Reviewer #1: Yes Reviewer #2: No ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: Yes Reviewer #2: Yes ****** Reviewer #1: The study is original and provides a comprehensive analysis of the costs of several techniques used in the monitoring and control of malaria. The MALDI-TOF technique is relatively new in the fields of entomology and parasitology, and the mosquito databases are developed in specialized laboratories rather than supplied by the companies that market the device. The technique is very advantageous in terms of cost, but time is needed to create a feasible database. With minor revisions, the article can be published. Reviewer #2: In general, the manuscript is well written, concise, and informative while results and figures reflect the work. As described by the authors, the study brings valuable information into the cost associated with MALDI-TOF which could directly impact research performed in areas lacking access to this technology. However, some overstatements and missing references might lead to speculative messages which must be avoided. All are described below for edits prior to publication. Tables 1 and 3 contain same results for MALDI-TOF blood meal and species ID. Why not combining both conditions? Lines 34-35 – Please edit to “... modest cost per sample may bring a paradigm shift in routine entomological surveillance in Africa.” Line 40 – Remove: “..., and regular...” Line 42 – Add “the” to “... the National Malaria...” Line 76 – Which 4 entomological parameters? Please add those to methods, not only to the results portion of the manuscript. Line 76 – Assumed? It was 15,000 samples, that is not subjective. Please delete “assumed”. Line 78 – Your “own experience”? Please avoid subjective terminology. Lines 79-82 – Assumed? Your study has considered that every laboratory had already the instrument, not assumed they had it. Please rephrase. Line 111 – Add to the main text the timeline related to the price estimates used in the study. It could be listed as: all pricing corresponds to a 2025 price list... This information can be easily referenced in the future by the scientific community. Line 130 – I understand the use of 2 staff members to perform the work. That wouldn’t make the cut for a true significant average, ideally you would have a minimum of 3 people performing the tasks. Please discuss that. Also, add a brief description of the level of expertise/training of each individual had prior to the study. If you had a highly experienced and a less experienced staff member performing the work, it should he mentioned. Line 145 – Why the labor cost considered the US salary and not the SSA base salary? It would be more appropriate for the application at the SSA, correct? Any additional cost comparison between them? Line 157-161 – Do you have a reference to sustain the 10% undetermined results? Avoid speculation. If that is in-house data, add that to the results and discuss it. Lines 179-180 – Random figure 1 legend. It was confusing to see the incomplete legend in the middle of the text. Line 229 – BM? Please edit table 2 on “blood meal” for consistency. Line 245 – Anything else besides Table 2? Line 259 – Investigation of a single hypothetical scenario, correct? Please remove the plural from the title. Line 239 – Remove bold from Direct on Table 4. Lines 262 and 265 - Table 5 typo. Line 266 – Correct to: “...the material, labor, total direct costs, and time-to-results...”. Also remove the bold from Table 5. Line 287 – Is it sensitivity or accuracy? Please reword. Line 299 – Bold statement. Due to several limitations regarding processing of complex samples (3-component samples – pathogen-vector-host), the use of MALDI-TOF for any vector-borne has several complicators not part of most medical microbiology systems. Please rephrase accordingly. ****** what does this mean? ). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy Reviewer #1: No Reviewer #2: No ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org Attachments Attachment Submitted filename: Article Review.docx https://doi.org/10.1371/journal.pone.0335764.r001
Revision 1
8 Oct 2025 Author Response Article Review PLOS ONE MALDI-TOF MS for malaria vector surveillance: a cost-comparison analysis using a decision-tree approach The article evaluates the use of MALDI-TOF MS as an alternative to molecular methods (PCR, ELISA, sequencing) for malaria vector surveillance in Kenya. The authors employ a decision-tree analytical model, with an annual volume of 15,000 processed mosquitoes, to compare material costs, personnel costs, and turnaround time. The results show that by adopting MALDI-TOF MS, the national surveillance program could achieve:74.48% time savings, up to 84% savings in material costs, 77% savings in labor costs, a total of 83% direct cost savings. The authors conclude that MALDI-TOF MS may bring about a paradigm shift in entomological surveillance in Africa. The strengths of the study lie in its high practical relevance – the article addresses a central issue in malaria control: the sustainability of vector surveillance in resource-limited countries. The described methodology is clear, employing a deterministic decision-tree model that is well justified and easy to follow. Costs are compared in a very detailed manner – the analysis includes materials, labor, direct costs, and time, providing a comprehensive picture. The data are applicable to public policies – the results can be used by decision-makers to optimize health budgets. An additional important strength is the study’s global relevance – although centered on Kenya, the conclusions can be extrapolated to other malaria-endemic countries. Limitations and critical observations Incomplete MALDI-TOF database – the method still has limitations in detecting Plasmodium infections and requires confirmation by ELISA, which reduces immediate practical advantages. Moreover, the article does not specify which database was used for mosquito detection, nor whether the database is already complete or still requires validation and expansion. A near-complete MALDI-TOF database exists for the An. gambiae (including An. gambiae s.s., An. arabiensis, An. merus, and An. quadriannulatus) and An. funestus (including An. funestus s.s., An. rivulorum, and An. leesoni) complexes — the major malaria vectors found in Kenya. The database used in this study is described in detail in reference [21]. Exclusion of maintenance and investment costs – the analysis ignores initial investments (equipment, staff training), which may underestimate the real costs of implementation in resource-limited countries. The MALDI-TOF device is expensive, and the amortization period compared to a classic PCR line should be specified. We agree with the reviewer that the MALDI-TOF device represents a significant capital investment. However, in our study, we did not include the initial investment or maintenance costs. This is because the device is already in use within microbiology laboratories for microbial identification, and its acquisition and upkeep have been budgeted for accordingly. Our approach was to repurpose existing MALDI-TOF infrastructure for entomological surveillance, thereby avoiding additional investment or operational costs specific to this application. Limited field validation – MALDI-TOF sensitivity and specificity for Plasmodium detection are based on controlled experiments rather than large field datasets. Thank you for this valuable comment. We agree that much of the validation for Plasmodium detection has relied on laboratory-infected mosquitoes, primarily because naturally infected field specimens are relatively rare. To address this limitation, we are now collaborating with several research groups to obtain a sufficient number of field-collected, Plasmodium-infected mosquitoes for MALDI-TOF MS database development and further validation. Generalizability – the study relies on the Kenyan NMCP context; its exact applicability in other countries may vary depending on existing infrastructure. We agree with your observation. Infrastructure availability indeed varies between countries. However, where MALDI-TOF MS devices are already in place—typically for clinical or microbiological applications—these can be repurposed for entomological surveillance with minimal additional investment. Furthermore, the establishment of regional reference laboratories could help mitigate infrastructure limitations by providing centralized support and access to MALDI-TOF MS technology for surrounding areas. In conclusion The article is well-written, rigorous, and makes a significant contribution to the field of entomological surveillance and cost optimization in malaria control. The results have practical value and are supported by a clear methodology. Recommendation Publication is recommended after minor revisions, in order to clarify development plans for the MALDI-TOF database for Plasmodium and for all mosquito species. It should also be specified that the MALDI-TOF device does not come with a built-in mosquito vector database and that such a database must be constructed separately for each region This has now been clearly detailed in the discussion Reviewer #2: In general, the manuscript is well written, concise, and informative while results and figures reflect the work. As described by the authors, the study brings valuable information into the cost associated with MALDI-TOF which could directly impact research performed in areas lacking access to this technology.However, some overstatements and missing references might lead to speculative messages which must be avoided. All are described below for edits prior to publication. Tables 1 and 3 contain same results for MALDI-TOF blood meal and species ID. Why not combining both conditions? Table 1 and 3 have been combined into one table; Table 1 Lines 34-35 – Please edit to “... modest cost per sample may bring a paradigm shift in routine entomological surveillance in Africa.” Lines 34-35 in the abstract section has been revised accordingly. Line 40 – Remove: “..., and regular...” Line 40 has been revised accordingly Line 42 – Add “the” to “... the National Malaria...” Line 42 has been revised accordingly Line 76 – Which 4 entomological parameters? Please add those to methods, not only to the results portion of the manuscript. Line 76 has been revised to include the parameters measured. It now reads three key entomological parameters (species identification, Plasmodium detection and blood meal analysis) Line 76 – Assumed? It was 15,000 samples, that is not subjective. Please delete “assumed”. Line 76 has been revised accordingly. The term assumed has been deleted. Line 78 – Your “own experience”? Please avoid subjective terminology. Line 78 has been revised accordingly. Lines 79-82 – Assumed? Your study has considered that every laboratory had already the instrument, not assumed they had it. Please rephrase. Lines 79-82 has been revised by replacing the word assumed with considered. Line 111 – Add to the main text the timeline related to the price estimates used in the study. It could be listed as: all pricing corresponds to a 2025 price list... This information can be easily referenced in the future by the scientific community. In Line 111 has been revised accordingly, this statement has been added: All pricing corresponds to a 2022 - 2023 price list. Line 130 – I understand the use of 2 staff members to perform the work. That wouldn’t make the cut for a true significant average, ideally you would have a minimum of 3 people performing the tasks. Please discuss that. Also, add a brief description of the level of expertise/training of each individual had prior to the study. If you had a highly experienced and a less experienced staff member performing the work, it should he mentioned. Thank you for your comment. We agree that having a minimum of three individuals would provide a more statistically robust estimate of the time required to perform the assays. However, due to logistical constraints, we were limited by the number of available staff. Only two individuals were available to carry out this exercise: a PhD student with extensive experience in the procedure and a laboratory technician with moderate experience. We believe their combined expertise provides a reasonable representation of the expected time required under typical laboratory conditions. Line 145 – Why the labor cost considered the US salary and not the SSA base salary? It would be more appropriate for the application at the SSA, correct? Any additional cost comparison between them? The labor cost was based on the KEMRI salary scale, in accordance with the structure approved by the Kenyan Salaries and Remuneration Commission (SRC). All costs were converted to USD using the exchange rate from the OANDA currency converter (https://www.oanda.com/currency-converter/en/) Line 157-161 – Do you have a reference to sustain the 10% undetermined results? Avoid speculation. If that is in-house data, add that to the results and discuss it. Line 157-161 – A reference [21] has been included. Lines 179-180 – Random figure 1 legend. It was confusing to see the incomplete legend in the middle of the text. This has been edited accordingly. The figure legend has been removed. Line 229 – BM? Please edit table 2 on “blood meal” for consistency. This has been edited accordingly Line 245 – Anything else besides Table 2? Labor cost is now in table 2 Line 259 – Investigation of a single hypothetical scenario, correct? Please remove the plural from the title. This line has been revised accordingly Line 239 – Remove bold from Direct on Table 4. This line has been revised accordingly Lines 262 and 265 - Table 5 typo. Corrected accordingly Line 266 – Correct to: “...the material, labor, total direct costs, and time-to-results...”. Also remove the bold from Table 5. This line has been revised accordingly Line 287 – Is it sensitivity or accuracy? Please reword. This line has been revised accordingly Line 299 – Bold statement. Due to several limitations regarding processing of complex samples (3-component samples – pathogen-vector-host), the use of MALDI-TOF for any vector-borne has several complicators not part of most medical microbiology systems. Please rephrase accordingly. This statement has been rephrased accordingly Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0335764.r002
15 Oct 2025 Decision Letter - Bersissa Kumsa, Editor MALDI-TOF MS for malaria vector surveillance: a cost-comparison analysis using a decision-tree approach PONE-D-25-38538R1 Dear Dr. Karisa, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support . If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Bersissa Kumsa, DVM, MSc, PhD Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0335764.r003
Formally Accepted
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