Molecular Evaluation of Conventional Microscopic Method Versus Fecal Antigen Capture Enzyme-Linked Immunosorbent Assay and Rapid Immunochromatographic Assay for Diagnosis of Cryptosporidium Infection

Abstract

Background: Cryptosporidiumhasemergedasanimportantcauseofdiarrheal illness worldwide, especially among young children and patients with immune deficiencies. Aim: The present study aimed to investigate the frequencyofCryptosporidium infection among suspected versus nonsuspected patients and to evaluate the performances of conventional microscopic assay, Cryptosporidium antigen detection enzyme-linked immunosorbent assay (CAD-ELISA), Crypto-Antigen Rapid Test (CA-RT), for diagnosis of Cryptosporidium infection using Cryptosporidium-specific polymerase chain reaction (CS-PCR) as criterion standard test. Methods: A total of 181 diarrheic stool samples including 105 from suspected patients and 76 from nonsuspected ones were collected. Results: The results revealed higher rate of infection among suspected patients (25% among diarrheic children, 24.2% among elderly/immune suppressed patients) as compared with nonsuspected patients (6.6% among immune-competent apparently healthy adults). Furthermore, conventional microscopic assay exhibited higher sensitivity (83.3%) as compared with CAD-ELISA (75%) and CA-RT (45.8%). On the other hand, higher specificity was shown for CA-RT (99.4%) and CAD-ELISA (98.7%) as compared with conventional assay (92.9%). Meanwhile, CA-RT and CAD-ELISA showed higher positive predictive values (91.7%, 90%) and lower negative predictive values (92.3%, 96.9%) than conventional assay (64.5%, 97.3%). Conclusions: No single test is perfect for diagnosis of cryptosporidiosis, anditisworthmentioningthatasignificantpercentageofCryptosporidium infections would have been missed if any of these assays had been the sole method of diagnosis. It is suggested to include an antigen detection immunoassay, preferably ELISA, in addition to microscopy for better diagnosis of Cryptosporidium infection.