Development of a salivary IgA detection method for accurate diagnosis of amebiasis

An amebiasis detection method was developed based on identifying anti-Entamoeba histolytica IgA in the saliva of infected individuals. The enzyme-linked immunosorbent assay (ELISA)-based detection method was tested along with microscopy and polymerase chain reaction (PCR) on saliva and stool samples from 110 asymptomatic individuals visiting the Manila Health Department - Public Health Laboratory of the City of Manila, Philippines. A receiver operating curve (ROC) was constructed to compare the ELISA results with PCR results. E. histolytica infection was detected in 18 of the 110 individuals. The developed method had an accuracy of 90%, sensitivity of 88.89%, specificity of 90.22%, positive predictive value of 64%, and negative predictive value of 97.65% if a 1:2 dilution of crude saliva sample in phosphate-buffered saline (PBS) was used for diagnosis when compared to PCR. The area under the curve (AUC) of the ROC was 0.9436 if a 1:2 dilution of a crude saliva sample was used. The developed assay presents an easy and accurate method of detecting amebiasis in infected individuals using saliva samples instead of stool or blood samples and has potential applications in both diagnosis and epidemiological studies.