Dipstick Assay Evaluated for Liver Fluke Diagnosis

A dipstick assay has been developed to diagnose fascioliasis, and its diagnostic efficacy evaluated in comparison to an immunoassay.

The dipstick uses excretory–secretory antigen from Fasciola gigantica dotted onto nitrocellulose paper using a sheet Mini-Protean II multiscreen apparatus to which human serum is applied.

Parasitologists at Ain Shams University (Cairo, Egypt) collected blood samples were collected from 60 individuals categorized into three groups. Group I consisted of 30 fascioliasis patients, diagnosed by detection of eggs of Fasciola in the stool and serologically by positive indirect hemagglutination test. Group II consisted of 20 patients with other parasitic diseases, and Group III consisted of 20 healthy individuals proven negative for fascioliasis and other parasitic diseases.

The enzyme linked immunosorbent assay (ELISA) was carried using a standard protocol and the absorbance was measured at 450 nm using a microplate reader. Samples were considered positive if their optical density was greater than the mean of healthy control samples plus three standard deviations. On the dipstick, a dark purple to brown band indicated a positive reaction.

The dipsticks' accuracy was 98.3%, with a sensitivity of 100%, a specificity of 96.7%, and negative predictive value of 100%. The sensitivity, specificity, and diagnostic accuracy of the ELISA were 100%, 96.7%, and 98.3%, respectively. The nitrocellulose paper and sheet Mini-Protean II multiscreen apparatus are both products of Bio-Rad (Hercules, CA, USA).

The authors concluded that the dipstick is a simple antigen and serum-conservative test requires only micrograms of parasite antigen and 20 µL of patient's sera. This test can be carried out while the patients wait, and would be more practical than what is currently done especially in rural areas and district hospitals. The test has its merit in being both qualitative, able to screen large numbers of blood samples, and quantitative assay, as the end-point titration of individual's sera can be determined. It is estimated that over 2.4 million people are infected with Fasciola species worldwide and around 91 million are at risk of infection. The study was published in the May 2012 issue of the journal Parasitology Research.

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Ain Shams University
Bio-Rad