Comparison of Commercial ELISA Kits to Confirm the Absence of Transmission in Malaria Elimination Settings

Abstract

Background: Antimalarial antibody measurements are useful because they reflect historical and recent exposure to malaria. As such, they may provide additional information to assess ongoing transmission in low endemic or pre-elimination settings where cases are rare. In addition, the absence of antibody responses in certain individuals can indicate the cessation of transmission. Commercial malaria enzyme-linked immunosorbent assays (ELISA) detect antimalarial antibodies and are commonly used to screen blood donations for possible malaria infection. However, there is no standardized test to detect antimalarial antibodies for epidemiological use. Here we compared five commercially available ELISA kits (Trinity Biotech, newbio, DiaPro, Cellabs, and NovaTec) in search of a standardized tool for supporting claims of absence of malaria transmission. For comparison, a research-based (RB) ELISA protocol was performed alongside the commercial kits. Results: The commercial kits were first compared using serum samples from known malaria-unexposed individuals ( n = 223) and Toxoplasma -infected individuals ( n = 191) to assess specificity and cross-reactivity against non-malaria infections. In addition, 134 samples from ≥10-year-olds collected in a hyperendemic region in the Gambia in the early 1990s were used to assess sensitivity. Three out of five kits showed high sensitivity (90–92%), high specificity (98–99%), low cross-reactivity (0–3%) and were considered user-friendly (Trinity Biotech, newbio and NovaTec). Two of these kits (Trinity Biotech and NovaTec) were taken forward for epidemiological evaluation and results were compared to those using the RB-ELISA. Samples from two pre-elimination settings (Praia, Cape Verde; n = 1,396, and Bataan, the Philippines; n = 1,824) were tested. Serological results from both the Trinity Biotech kit and the RB-ELISA concurred with recent passively detected case counts in both settings. Results from the Trinity Biotech kit reflected a significant decrease in the number of reported cases in Bataan in the 1990s better than the RB-ELISA. Results from the NovaTec kit did not reflect transmission patterns in either setting. Conclusion: The Trinity Biotech commercial ELISA kit was considered reliable for epidemiological use and accurately described transmission patterns in two (previously) malaria endemic settings. The use of this simple and standardized serological tool may aid national control and elimination programs by confirming that regions are free from malaria.

Analytical approaches for antimalarial antibody responses to confirm historical and recent malaria transmission: an example from the Philippines

“…Our results are able to confirm the absence of P. falciparum and P. vivax transmission in malaria-free Bataan for the age groups 10 and below, providing evidence for its malaria elimination status. Moreover, the change point in transmission for Bataan is estimated higher but still consistent with the results of a serological survey conducted in the same area a year prior, which estimated the change point at 22 years (van den Hoogen et al, 2020a) , and coincided with the decline in cases in the municipality. For Occidental Mindoro, the interruption in transmission from 7-12 years ago may be explained by the extensive malaria control activities implemented in the area, as the province has been part of the priority provinces of the Global Fund for Malaria since the 2000s.…”

“…The validation data included a P. falciparum and P. vivax -positive group with African positive controls, as well as clinical samples from a Malaysia study (Fornace et al, 2019) and this study. The malaria-negative group consisted of European malaria-naïve samples, and Philippine malaria-negative samples from individuals under 10 years of age in a 2017 cross-sectional study in Bataan (van den Hoogen et al, 2020a) and this study. For the negative population model, the European samples were used as reference population.…”

Diagnostic Methods for Non-Falciparum Malaria

“…Currently, there are commercial ELISA kits to detect antimalarial antibodies. The performance of five commercial kits (Bio-Rad/Trinity Biotech, Newbio, DiaPro, Cellabs and NovaTec), all detecting pan-Plasmodium spp anti-antibodies, was evaluated in a recent study (van den Hoogen et al, 2020). Specificity (vs. malaria unexposed donors or samples positive to Toxoplasma) was 96% except for the Cellabs kit (81-84%) and sensitivity ranged 90-95% except for the DiaPro kit (86%).…”

Plasmodium knowlesi: the game changer for malaria eradication

“…Despite of its limited use in diagnosing acute infections, serological assay plays an important role in malaria disease surveillance, screening in blood donation centres, and identification of parasite exposure history [ 102 ]. There are several malaria ELISA kits that detect anti- Plasmodium antibodies.…”