Fig 1.
Flowchart for the study methodology.
This study followed three main steps including the development of the new ELISA assay followed by its analytical validation using a training set of clinical samples (Cases and Controls), and, finally, its implementation during a real-world epidemiological survey.
Fig 2.
Comparison of the level of anti-H. pylori IgG antibodies between H. pylori negative and positive samples.
This figure compares the rates of anti-H. pylori IgG antibodies between H. pylori negative and positive patients in the training set whose status had been established by standard invasive tests (i.e., histology, culture, and rapid urease test). Hence, medians of antibodies rates with interquartile intervals (IQR) were 45.0 (IQR: 75.2) and 11.9 (IQR: 7.3) U/mL respectively in H. pylori positive and negative patients. The difference of anti-H. pylori IgG levels between the two groups of patients was statistically significant (p = <0.001).
Fig 3.
ROC/AUC and best cut-of-value of the HpAfr-ELISA assay in the training set.
The plot displayed on this figure represent the ROC (receiver operating characteristic) and the AUC (Area under the ROC Curve) obtained with HpAfr-ELISA on the training set using the H. pylori status by standard invasive tests (i.e., histology, culture, and rapid urease test) as reference. This plot indicates that the ROC curve of HpAfr-ELISA had an AUC of 97.6% with its best cut-of-value being 20.2 U/mL of anti-H. pylori IgG.
Fig 4.
Sensitivity and specificity of the HpAfr-ELISA assay in the training set.
This plot indicates that the HpAfr-ELISA assay had a sensitivity of 96.7% (dashed blue line) and a specificity of 90.0% (dashed red line) when considering its best cut-off-value (dashed black line) defined at the Youden index of the dataset (the point with the maximum specificity + sensitivity).
Fig 5.
Comparison of ROCs/AUCs of the HpAfr-ELISA assay at three repeated testing.
Plots displayed on the figure represent ROC curves and AUCs obtained at repeated tests (test 1, test 2, and test 3) on the training set in intra-observer. No significant difference between the ROC curve was noted (p>0.05).
Table 1.
Qualitative agreement of HpAfr-ELISA outcomes at two repeated testing.
Table 2.
Quantitative agreement of HpAfr-ELISA outcomes at two repeated testing.
Table 3.
Bayesian estimation of the latent diagnostic performance of HpAfr-ELISA in the absence of a perfect gold standard test.
Table 4.
Bayesian estimation of the latent true prevalence of the H. pylori infection and the dyspeptic syndrome in the study population.
Table 5.
Baseline socio-demographic characteristics of study participants (n = 425).
Table 6.
Baseline clinical characteristics of study participants (n = 425).
Table 7.
Characterization of the dyspepsia in study participants.
Table 8.
Logistic regression models detecting factors that predict the H. pylori seropositivity in the study population*.