Rapid Microfluidic Immunoassay Detects Cryptosporidium in Remote Areas

A lab-on-a-chip device has been developed that can rapidly diagnose Cryptosporidium infections from just a finger prick, potentially bringing point-of-care diagnosis to at-risk in rural areas in order to improve treatment outcomes.

For a healthy individual, an infection of Cryptosporidium parvum may mean nothing more than a few days of bad diarrhea but for someone with a compromised immune system it can mean death, following an excruciating, protracted bout of watery diarrhea.

Scientists at Fudan University (Shanghai, China) developed a novel microfluidic immunochip system for the surveillance and the rapid detection of Cryptosporidium infection in 190 human immunodeficiency virus (HIV)-infected patients from Guangxi (China), using the P23 antigen of Cryptosporidium. The chip has a number of advantages; it is small, at 3 cm by 2 cm, and costs around USD 1 to manufacture. Furthermore, it is capable of detecting the antigen in 10 minutes using 2 µL blood sample volumes. The investigators also noted that the device is easy to operate, and has the ability to process up to five samples at a time.

The production of a microfluidic chip was designed using AutoCAD software (Autodesk Inc.; San Rafael, CA, USA) and manufactured from polydimethylsiloxane (PDMS), a widely used silicon-based organic polymer. The chip comprises of functional valves, pumps and columns, sitting in the middle of a platform of reagent cartridges, an injection pump, a fluorescence microscope and a digital camera. The system also was evaluated using the standard enzyme-linked immunosorbent assay (ELISA) method.

Among 190 HIV-infected individuals, the rate of P23 positivity was 13.7%. Seropositivity in HIV-infected individuals was higher in female patients. The seropositivity to P23 was higher in HIV-infected individuals with high viral load, although the difference was statistically insignificant. Significantly higher Cryptosporidium seropositivity was observed in HIV-infected individuals with a CD4+ T-cell count of less than 200 cells/μL than in those with equal to or greater than 200 cells/μL. The results also demonstrated that a lower CD4+ T-cell count may reflect an increased accumulated risk for cryptosporidiosis.

The authors concluded that as the detection system was further validated using the standard ELISA method, a good correlation between the two methods was found. Under the same sensitivity, this new microfluidic chip device had a specificity of 98.2%. This developed system may provide a powerful platform for the fast screening of Cryptosporidium infection in HIV-infected patients. The study was published online on April 15, 2015, in the journal Biomicrofluidics.

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