Development of enzyme-linked immunosorbent assay for serodiagnosis of human paragonimiasis

Background & objectives: Although human paragonimiasis is known to occur in Manipur and Arunachal Pradesh, there is no indigenous immunodiagnostic test available in India. Sputum examination for detection of eggs is less sensitive method for diagnosis of paragonimiasis and unfortunately, the eggs are not always present in the sputum of infected individuals. Due to overlapping clinical manifestations and similarities between X-ray picture in pulmonary paragonimiasis and pulmonary tuberculosis, chances of diagnostic confusion can increase. Therefore, the objective of this study was to develop an ELISA test indigenously for diagnosis of paragonimiasis. Methods: Somatic (S) and excretory-secretory (ES) antigens of adult trematodes belonging to genus Paragonimus were prepared. Serum samples were collected from 22 confirmed patients of paragonimiasis and from five groups of negative controls. The cut-off points for both types of antigens were calculated using receiver operating characteristic (ROC) curve analysis. The sensitivity, specificity, predictive values and efficiency of the,ELISA tests were also calculated. Results: IgG-ELISA test using either S or ES antigens were 100 per cent sensitive yet the utility of S antigen for diagnosis of paragonimiasis seemed to be less reliable because of low specificity (91.3%). On the other hand, ES antigen was more reliable with 100 per cent specificity as no false positive cases were recorded. Interpretation & conclusion: ES antigen can be effectively used for screening large populations for paragonimiasis. In areas where both paragonimiasis and tuberculosis are endemic, suspected subjects should be screened for both the diseases because of chance of mistaken diagnosis. Correct diagnosis will avoid unnecessary costly treatment.