Fig 1.
Frequencies of helminth and Plasmodium falciparum single infections and polyparasitism in the study cohort.
Rows represent the number of infections by parasite (sets) and columns represent the frequency of single infections and coinfections (intersections) when helminth infection was detected by microscopy (A), qPCR (B) or the combination of both (C). In all cases, infection of P. falciparum was detected by qPCR. In the case of helminth detection by qPCR, there were 25 samples for which helminth qPCR was not available. Filled dots show which set is part of an intersection and when more than one set is involved, they are connected by lines. At the bottom, the sample size and percentage of single infections of polyparasitism with respect to the total of infected individuals are indicated.
Fig 2.
Areas under the curve from receiver operating characteristic curve analysis for helminth-specific IgG levels in the whole population (A) or stratified by age (B). Dashed lines represent the accuracy thresholds: null if AUC < 0.5, low if 0.5 ≤ AUC > 0.7, moderate if 0.7 ≤ AUC > 0.9 and high if AUC ≥ 0.9. AUC: Area Under the Curve; CI: Confidence Interval; M: Microscopy; P: qPCR; MP: Microscopy and qPCR combined. Asc: Ascaris spp.; Hoo: Hookworm; Tri: Trichuris spp.; Str: Strongyloides stercoralis; Sch: Schistosoma spp.; Sh: Schistosoma haematobium; Sm: Schistosoma mansoni. Complementary information for this figure can be found in S2 Table.
Fig 3.
Receiver operating characteristic curves and their corresponding areas under the curve from the best performing IgG responses in detecting current helminths infection.
IgG responses (log10-transformed median fluorescence intensity [MFI] levels) against S. stercoralis (NIE) and Schistosoma spp. (MEA and Sm25) antigens in serum samples from 715 endemic individuals and 50 Spanish donors were used as predictor variables. Microscopic (M), qPCR (P) or the combination of both (MP) diagnoses were used as response variables. S spp.: Schistosoma spp.; Sh: Schistosoma haematobium; Sm: Schistosoma mansoni. AUC: Area Under the Curve.
Fig 4.
Areas under the curve from receiver operating characteristic curve analysis for total IgE.
The performance of total IgE levels to detect helminth or Plasmodium falciparum infections in the whole population is shown in A and stratified by age in B. Dashed lines represent the accuracy thresholds: null if AUC < 0.5, low if 0.5 ≤ AUC > 0.7, moderate if 0.7 ≤ AUC > 0.9 and high if AUC ≥ 0.9. AUC: Area Under the Curve; CI: Confidence Interval; M: Microscopy; P: qPCR; MP: Microscopy and qPCR combined. Asc: Ascaris spp.; Hoo: Hookworm; Tri: Trichuris spp.; Str: Strongyloides stercoralis; Sch: Schistosoma spp. Hel: Helminths; Pf: Plasmodium falciparum.; Sh: Schistosoma haematobium; Sm: Schistosoma mansoni. Complementary information for this figure can be found in S2 and S3 Tables.
Fig 5.
Receiver operating characteristic curves and their corresponding areas under the curve from the best performing total IgE responses in detecting current hookworm and Schistosoma spp. infection.
Total IgE responses (log10-transformed median fluorescence intensity levels) in serum samples from 715 endemic individuals were used as predictor variable. Microscopic (M), qPCR (P) or the combination of both (MP) diagnoses for hookworm and Schistosoma spp. were used as response variables. DX: diagnosis; S spp.: Schistosoma spp.; Sh: Schistosoma haematobium; Sm: Schistosoma mansoni; AUC: Area Under the Curve.
Fig 6.
Receiver operating characteristic curves and their corresponding areas under the curve from the best performing IgG responses in detecting current Plasmodium falciparum infection.
A. IgG responses (log10-transformed median fluorescence intensity [MFI] levels) against LSA1, EXP1, AMA1, EBA175, MSP142, MSP2, MSP3, MSP5, Rh1 and PTRAMP in serum samples from 715 endemic individuals and 50 Spanish donors were used as predictor variables and qPCR results as response variable. B. IgG responses (log10-transformed MFI levels) against EXP1, AMA1 and MSP2 in serum samples from children (N = 363) and adults (N = 352) were used as predictor variables and qPCR results were used as response variable. In each age group, antibody levels in samples from the 50 Spanish donors were used as negative controls. AUC: Area Under the Curve.
Fig 7.
Helminth and Plasmodium falciparum antigen-specific IgG levels in non-endemic and endemic populations and seropositivity cutoffs calculated by different methods.
Antibody levels are presented as the log10-transformed median fluorescence intensity (MFI) of IgG against Strongyloides stercoralis (NIE), Schistosoma spp. (Sm25 and MEA) and P. falciparum (EXP1, AMA1 and MSP2) antigens. In the endemic population, filled dots highlight individuals with a helminth infection with the corresponding parasite for each antigen detected by microscopy and/or qPCR in the case of helminths and qPCR in the case of P. falciparum. The boxplots represent the median (bold line), the mean (black diamond), the first and third quartiles (box) and the largest and smallest values within 1.5 times the interquartile range (whiskers). Data beyond the end of the whiskers are outliers. Cutoff95SE: cutoff prioritizing a minimum sensitivity of 95%; Cutoff95SP: cutoff prioritizing a minimum specificity of 95%; CutoffYI: cutoff corresponding to the maximum Youden’s Index; CutoffEM: cutoff defined by the Expectation-Maximization algorithm; CutoffNC: cutoff calculated as mean + 3*standard deviations of the log10-transformed MFI levels from the non-endemic population. NE: Non-Endemic (N = 50), E: Endemic (N = 715). The rest of the antigens are in S2 and S3 Figs.
Fig 8.
Effect of single infections on IgG levels to other infections.
Only individuals with single infections or no infections at all detected by the combination of microscopy and qPCR are shown. Antibody levels are presented as the log10-transformed median fluorescence intensity (MFI) of IgG against Strongyloides stercoralis (NIE), Schistosoma spp. (Sm25 and MEA) and P. falciparum (EXP1, AMA1 and MSP2) antigens. For each antigen, antibody levels for each species were compared to the levels of those with no infection and the corresponding species to the antigen was shown as a reference. Statistical comparison between groups was performed by Wilcoxon rank-sum test and the adjusted P values by the Holm approach are shown. Statistically significant P values are highlighted in bold. The sample size of each group is shown below each boxplot. The boxplots represent the median (bold line), the mean (black diamond), the first and third quartiles (box) and the largest and smallest values within 1.5 times the interquartile range (whiskers). Data beyond the end of the whiskers are outliers. Cutoff95SE: cutoff prioritizing a minimum sensitivity of 95%; Cutoff95SP: cutoff prioritizing a minimum specificity of 95%; CutoffYI: cutoff corresponding to the maximum Youden’s Index; CutoffEM: cutoff defined by the Expectation-Maximization algorithm; CutoffNC: cutoff calculated as mean + 3*standard deviations of the log10-transformed MFI levels from the non-endemic population. Asc: Ascaris spp.; Hoo: Hookworm; Tri: Trichuris spp.; Str: Strongyloides stercoralis; Sch: Schistosoma spp. Hel: Helminths; Pf: Plasmodium falciparum. The rest of the antigens are in S4 and S5 Figs.
Fig 9.
Helminth antigen-specific IgG levels in non-endemic and endemic populations and seropositivity cutoffs by the Expectation-Maximization algorithm.
Antibody levels are presented as the log10-transformed median fluorescence intensity (MFI) of IgG against helminth antigens. In the endemic population, filled dots highlight individuals with a helminth infection with the corresponding parasite for each antigen detected by microscopy and/or qPCR. The dashed line represents the serology cutoff calculated with the Expectation-Maximization algorithm. Individuals above (orange) or below (grey) this cutoff were considered seropositive or seronegative, respectively. At the top of each plot, the absolute number and percentage of seropositive individuals with respect to the Non-Endemic (NE) (N = 50) or Endemic (E) (N = 715) populations are indicated. The boxplots represent the median (bold line), the mean (black diamond), the first and third quartiles (box) and the largest and smallest values within 1.5 times the interquartile range (whiskers). Data beyond the end of the whiskers are outliers.
Fig 10.
Plasmodium falciparum antigen-specific IgG levels in non-endemic and endemic populations and seropositivity cutoffs by the Expectation-Maximization algorithm.
Antibody levels are presented as the log10-transformed median fluorescence intensity (MFI) of IgG against P. falciparum antigens. In the endemic population, filled dots highlight individuals with a P. falciparum infection detected by qPCR. The dashed line represents the serology cutoff calculated with the Expectation-Maximization algorithm. Individuals above (orange) or below (grey) this cutoff were considered seropositive or seronegative, respectively. At the top of each plot, the absolute number and percentage of seropositive individuals with respect to the Non-Endemic (NE) (N = 50) or Endemic (E) (N = 715) populations are indicated. The boxplots represent the median (bold line), the mean (black diamond), the first and third quartiles (box) and the largest and smallest values within 1.5 times the interquartile range (whiskers). Data beyond the end of the whiskers are outliers.