Urinary Dipstick Tested for Intestinal Schistosomiasis

The Urine Circulating Cathodic Antigen (CCA) dipstick has been tested as a substitute for microscopy for mapping and point-of-care (POC) diagnosis of intestinal schistosomiasis.

The diagnostic performance of a commercially available urinary CCA dipstick test has been compared to that of fecal microscopy for POC diagnosis in preschool-aged children.

Scientists at the Liverpool School of Tropical Medicine (Liverpool, UK) working with colleagues in Uganda recruited a total of 925 children whose mean age was 2.8 years, from six lakeshore villages representative of high, moderate and low levels of disease transmission. At baseline, all children were tested for intestinal schistosomiasis by microscopic examination of duplicate Kato-Katz smears prepared from a single stool; by antigen detection with the urine CCA immunochromatographic dipstick; and by serology with a commercially available enzyme-linked immunosorbent assay (ELISA; IVD Inc.; Carlsbad, CA, USA) that measures host antibody titers to soluble egg antigens.

In low, moderate, and high transmission settings, the observed prevalence of egg-patent schistosomiasis according to fecal microscopy was 7.2%, 16.9% and 38.8% before treatment, and 6.9%, 25.0% and 47.5% one year after treatment. In low, moderate, and high transmission settings, the observed prevalence of Schistosoma mansoni infections according to CCA dipsticks (Rapid Medical Diagnostics; Pretoria, Republic of South Africa) was 45.9%, 45.4% and 56.1% before treatment, and 39.6%, 44.8% and 55.9% one year after treatment, respectively. Most of the positive diagnoses were single positive reactions, with few double and triple positive reaction recorded.

According to the ELISA results, the observed prevalence of S. mansoni infections was 36.0%, 49.0%, and 81.6% before treatment and 18.4%, 52.8%, and 92.0% one year after treatment, in low, moderate, and high transmission settings, respectively. As a point-of-care diagnosis, the urine CCA dipstick achieved sensitivity values ranging from 52.5% to 63.2% and specificity values of 57.7% to 75.6%. Fecal microscopy achieved very high specificities of greater than 87%, but sensitivities as low as 16.7% in the low transmission setting.

The authors concluded that the CCA is a viable alternative for diagnosis of S. mansoni infections in preschool-aged children, particularly in low transmission settings or in areas where treatment has reduced prevalence to low levels. The urine CCA commercial test was proven more sensitive than fecal smears for mapping proposes, and it was as reliable as fecal microscopy for point-of-care diagnosis. The study was published on January 24, 2013, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Liverpool School of Tropical Medicine
IVD Inc.
Rapid Medical Diagnostics