We demonstrate how point-of-care testing (POCT) can help transition risk avoidance to risk management during the COVID-19 crisis by applying sound geospatial strategies to a “hotspot.” We use the example of a border province in Cambodia to illustrate principles of implementing COVID-19 POCT in a limited-resource setting.
Our goals are a) to strategize high volume of COVID-19 testing to detect outbreaks quickly and limit their spread in Cambodia, b) to analyse public accessibility to COVID-19 testing, and c) to enhance awareness of COVID-19 test performance over the entire range of prevalence.
We collected public health reports regarding testing, COVID-19 assay performance, and options from PubMed, the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the World Health Organization (WHO), the Phnom Penh Post, the Khmer Times, manufacturer fact sheets, and public domain sources in Cambodia.
We explored articles on COVID-19 outbreaks, geographic prevalence, and lockdowns in Cambodia. We analysed data using fundamental equations from Kost GJ, then visualised them with Desmos Graphing Calculator, Mathematica, Symbolab Math, and Wolfram Alpha Widgets. This work was approved by the Ethics Committee of the University of Puthisastra.
High-resource countries, such as the United States, conducted ~1.5 million tests per one million population each day in end-May 2021, while Cambodia tested at least 20 times fewer people. Of numerous commercialised tests and diagnostic kits available globally, Cambodia is limited in testing capacity to sparsely placed real time-polymerase chain reaction (RT-PCR) assays and antigen rapid detection tests (Ag-RDTs).
There is no national standardisation nor uniform policy to guide rural healthcare facilities in use of rapid COVID-19 diagnosis or their quality control. RT-PCR is performed using the Biorad cfx 96, GeneXpert Dx, Cobas 6800, and Cobas Z480, while Ag-RDTs comprise the Panbio COVID-19 Ag RDT and the Roche Diagnostics SARS-CoV2 Rapid Antigen Test.
Testing sites are concentrated in metropolitan areas, while just a few are located in rural provinces. Ag RDT is officially permitted for use by private health facilities. PCR testing is available at national testing laboratories in Phnom Penh, Siemreap, Battambang, Sihanoukville, and Banteay Meanchey (Cambodia-Japan Friendship Mongkul Borey Provincial Hospital). Phnom Penh has 11 testing sites while most provinces have only one testing site located at the provincial referral hospital.
SARS-CoV-2 antigen tests in Cambodia will be most useful in settings of low prevalence, as shown by predictive value geometric mean-squared (PV GM2) visual logistics (Figure 1). Factors affecting antigen test performance include age (children), environmental stress (uncontrolled temperature), drive-through conditions, and expertise at swabbing. Additional challenges include environmental conditions and use of POCT in emergency settings.
Figure 1. Visual logistics — Understanding and using COVID-19 antigen tests.
Factors affecting antigen test performance shown as PV GM2 comprise age, environmental stress, drive-through conditions, and expertise at swabbing, as wells as testing at points of care and in emergency settings, as illustrated in this figure.
Smaller towns in Banteay Meachey Province, our focus region, deemed a COVID-19 “hotspot” by the MOH, are experiencing high COVID-19 infection rates (Figure 2). This province shares an international border with Thailand. Human migration adds to risk, contagion, and the need for rapid diagnosis. Rapid testing can be appropriately placed and easily accessible close to the border.
Among 72 available public health facilities in this province, only three main hospitals offer COVID-19 testing — Cambodia-Japan Friendship Mongkul Borey Provincial Hospital, Serey Sorphorn Referral Hospital, and Poipet Referral Hospital. The first one provides RT-PCR testing using the GeneXpert, and the others, rapid antigen testing (see Figure 2).
Figure 2. Banteay Meanchey Province, human migration, and spread of contagion in Cambodia — the role of rapid POC diagnostics.
Cambodians own Leung Ke market shops in Thailand. They make regular visits to Thai hospitals. That mingling brings COVID-19 contagion and other problems to bear on the healthcare small-world network of the neighboring province in Cambodia.
From geospatial analysis, people must travel an average of 43 (SD 24) kilometres or about 85 (SD 48) minutes one way by motorcycle to obtain RT-PCR testing at Cambodia-Japan Friendship Mongkul Borey Provincial Hospital (Table 1). Queuing time, return trip, large families, and wages lost diminish motivation to make the trips. Figure 2 provides a medically and economically effective solution by moving testing closer to the actual sites of community need.
Strategic risk management through quick access to COVID-19 testing will benefit the capital, Phnom Penh, and rural areas. COVID-19 waves in rural Thailand and daily human migration call for rapid antigen testing to avoid risk. Scaling up of rapid antigen tests at health facilities in rural and border areas identified by geospatial analysis will enhance early detection at points of need.
RT-PCR should be placed in Poipet Referral Hospital (see Figure 2) to identify infections near the border where residents cross to Thai markets, healthcare sites, and in better times, casinos. Rapid antigen testing made available in Phnom Srok, Preah Neth Preah, Malai Health Center, and others will facilitate care of non-COVID-19 emergencies (e.g., acute myocardial infarction and motor vehicle accidents). That is, rapid identification of SARS-CoV-2 infected patients will help keep healthcare personnel safe.
Several point-of-care strategies represent proven COVID-19 solutions — drive-through and walk-up sites, self-swabbing, and mobile vans for immigration, airports, residences, schools, sports, markets, factories, and numerous others — basically, wherever testing is needed. For example, mobile drive-thru testing implemented in Solano County, California, U.S. (Figure 3) represents a valuable solution that Cambodia can develop to promote resilience through rapid evidence-based decision-making directly at sites of need in communities.
Figure 3. Mobile van equipped with five types of COVID-19 tests used to detect and manage outbreaks in small communities in America.
Recommendations and future vision
With limited resources, Cambodia should carefully and urgently devise a national testing plan by employing geospatial analysis, transit time metrics, and strategic mappings to avoid and manage COVID-19 risk and outbreaks (Table 2).
Performance analysis with visual logistics for pattern recognition will help health providers to select appropriate test formats and optimize COVID-19 diagnostics in different settings, environmental conditions, and community prevalence.
Mobile, drive-through, and walk-up POCT will allow public health practitioners to detect outbreaks and limit their spread, especially in crowded places like markets, regions of human migration, and daily transits across borders.
As geographic needs transition from risk avoidance to risk management, national leadership should establish POCT policy, guidelines, and plans for highly infectious diseases to achieve equitable access to diagnostic tests as well as vaccinations, which go hand-in-hand to end the pandemic.Acknowledgements
This work was supported by the Point-of-Care Testing Center for Teaching and Research (POCT•CTR), School of Medicine, UC Davis; by Dr. Kost, Director; and by a Fulbright Scholar Award (GK) 2020-2022, ASEAN Program. Figures and tables were provided courtesy and permission of Knowledge Optimization, Davis, California, which reserves all rights to this work and grants Omnia Health Magazine the one-time permission to publish this work digitally as a proceedings report of the Medlab Middle East presentation by Dr. Kost, which rendition does not preclude publication in a medical journal.
Kost GJ. Designing and interpreting Coronavirus Disease 2019 (COVID-19) diagnostics: Mathematics, visual logistics, and low prevalence. Arch Pathol Lab Med. 2021;145(3):291-307. doi: 10.5858/arpa.2020-0443-SA. [open access]
Kost GJ. The impact of increasing prevalence, false omissions, and diagnostic uncertainty on Coronavirus Disease 2019 (COVID-19) test performance. Arch Pathol Lab Med. 2021 Mar 8. doi: 10.5858/arpa.2020-0716-SA. Epub ahead of print. [open access]
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