Type of infection by pathogenic intestinal parasite: relative frequencies (%), absolute frequencies (n) and confidence intervals of 95% (IC95%).

<p>Type of infection by pathogenic intestinal parasite: relative frequencies (%), absolute frequencies (n) and confidence intervals of 95% (IC95%).</p

Binary regression for infection by pathogenic intestinal parasite.

<p>% (n)–relative and absolute frequencies of infected children; <i>p</i>—refers to the comparison of the ratio of the variable classes; OR—Odds Ratio; IC95% (OR)—confidence interval at 95% of the estimated odds ratio; (ref.)—reference category for OR</p><p>a–Pearson Chi-square test</p><p>Binary regression for infection by pathogenic intestinal parasite.</p

Level of stunting and anemia (n = 328): relative frequencies (%), absolute frequencies (n) and confidence intervals of 95% (IC95%).

<p>Level of stunting and anemia (n = 328): relative frequencies (%), absolute frequencies (n) and confidence intervals of 95% (IC95%).</p

Multivariate regression model for stunting.

<p>% (n)–relative and absolute frequencies of stunted children; OR Adjusted—Odds Ratio Adjusted for confounders; IC95% (OR Adjusted)—confidence interval at 95% of the estimated adjusted odds ratio</p><p><i>p</i>^a—<i>p</i> refers to test the significance of each parameter levels in each factor (H₀:OR = 1, hypothesis of no association); R² (%)—percentage coefficient of determination of the model according to Nagelkerke</p><p><i>p</i>^b—<i>p</i> refers to the significance level of the Omnibus test of model coefficients</p><p><i>p</i>^c—<i>p</i> refers to the significance level of the Hosmer and Lemeshow test on the good fit of the model; (ref.)—reference category for OR</p><p>Multivariate regression model for stunting.</p

Binary regression for stunting and anemia.

<p>% (n)–relative and absolute frequencies of stunted or anemic children; <i>p</i>—refers to the comparison of the ratio of the variable classes; OR—Odds Ratio; IC95% (OR)—confidence interval at 95% of the estimated odds ratio</p><p>^a–Pearson Chi-square test</p><p>^b—Fisher's Exact test; (ref.)—reference category for OR</p><p>1—test with robustness problems, 12.5% of the expected frequencies below 5</p><p>Binary regression for stunting and anemia.</p

Multivariate regression model for anemia

<p>% (n)–relative and absolute frequencies of anemic children; OR Adjusted—Odds Ratio Adjusted for confounders; IC95% (OR Adjusted)—confidence interval at 95% of the estimated adjusted odds ratio</p><p><i>p</i>^a—<i>p</i> refers to test the significance of each parameter levels in each factor (H₀:OR = 1, hypothesis of no association); R² (%)—percentage coefficient of determination of the model according to Nagelkerke</p><p><i>p</i>^b—<i>p</i> refers to the significance level of the Omnibus test of model coefficients</p><p><i>p</i>^c—<i>p</i> refers to the significance level of the Hosmer and Lemeshow test on the good fit of the model; (ref.)—reference category for OR</p><p>Multivariate regression model for anemia</p

HRP2 bead assay only detects HRP2-producing <i>P</i>. <i>falciparum</i>.

<p>Plasma from non-infected persons, or persons with symptomatic <i>Plasmodium</i> spp. infection was assayed at a 1:10x dilution for presence of HRP2. <b>P. mal</b>: <i>P</i>. <i>malariae</i>; <b>P. ova</b>: <i>P</i>. <i>ovale</i>.</p

Bead-based immunoassay allows sub-picogram detection of histidine-rich protein 2 from <i>Plasmodium falciparum</i> and estimates reliability of malaria rapid diagnostic tests

<div><p>Detection of histidine-rich protein 2 (HRP2) from the malaria parasite <i>Plasmodium falciparum</i> provides evidence for active or recent infection, and is utilized for both diagnostic and surveillance purposes, but current laboratory immunoassays for HRP2 are hindered by low sensitivities and high costs. Here we present a new HRP2 immunoassay based on antigen capture through a bead-based system capable of detecting HRP2 at sub-picogram levels. The assay is highly specific and cost-effective, allowing fast processing and screening of large numbers of samples. We utilized the assay to assess results of HRP2-based rapid diagnostic tests (RDTs) in different <i>P</i>. <i>falciparum</i> transmission settings, generating estimates for true performance in the field. Through this method of external validation, HRP2 RDTs were found to perform well in the high-endemic areas of Mozambique and Angola with 86.4% and 73.9% of persons with HRP2 in their blood testing positive by RDTs, respectively, and false-positive rates of 4.3% and 0.5%. However, in the low-endemic setting of Haiti, only 14.5% of persons found to be HRP2 positive by the bead assay were RDT positive. Additionally, 62.5% of Haitians showing a positive RDT test had no detectable HRP2 by the bead assay, likely indicating that these were false positive tests. In addition to RDT validation, HRP2 biomass was assessed for the populations in these different settings, and may provide an additional metric by which to estimate <i>P</i>. <i>falciparum</i> transmission intensity and measure the impact of interventions.</p></div

Test comparison between bead assay and HRP2 RDTs.

<p>(<b>A</b>) Persons from Mozambique tested for presence of HRP2 by RDT (SD Bioline Pf) and bead assay, and comparison statistics for the two tests. For this purpose, the RDT was treated as the standard classification predictor and the bead assay as the novel test. The same analysis in (<b>B</b>) for persons from Angola where the SD Bioline Malaria Ag P.f/P.v RDT was used and in (<b>C</b>) Haiti where the First Response HRP2 RDT was used.</p

Comparison of bead-based HRP2 assay with HRP2 ELISA.

<p>(<b>A</b>) Completed scaffolding of bead complex when HRP2 is present in a sample. (<b>B</b>) Serial dilutions of Type A, B, and C rHRP2 assayed by bead assay (solid lines) and ELISA (hashed lines), and (<b>C</b>) comparison of signal intensities of same dilutions between bead assay and ELISA. (<b>D</b>) Serial dilutions of cultured <i>P</i>. <i>falciparum</i> strains assayed by bead assay (solid lines) and ELISA (hashed lines), and (<b>E</b>) scatterplot for signal intensities of same dilutions between immunoassays. Vertical and horizontal dashed lines in (<b>C</b>) and (<b>E</b>) represent lower limits of reliable detection for the ELISA and bead assay, respectively.</p