Environmentally Resilient Microfluidic Point-of-Care Immunoassay Enables Rapid Diagnosis of Talaromycosis

Point-of-care tests (POCTs) are increasingly being used in field settings, particularly outdoors. The performance of current POCTs-most commonly the lateral flow immunoassay-can be adversely affected by ambient temperature and humidity. We developed a self-contained immunoassay platform-the D4 POCT-that can be conducted at the POC by integrating all reagents in a capillary-driven passive microfluidic cassette that minimizes user intervention. The assay can be imaged and analyzed on a portable fluorescence reader-the D4Scope-and provide quantitative outputs. Here, we systematically investigated the resilience of our D4 POCT to varied temperature and humidity and to physiologically diverse human whole blood samples that span a wide range of physiological hematocrit (30-65%). For all conditions, we showed that the platform maintained high sensitivity (0.05-0.41 ng/mL limits of detection). The platform also demonstrated good accuracy in reporting true analyte concentration across environmental extremes when compared to the manually operated format of the same test to detect a model analyte-ovalbumin. Additionally, we engineered an improved version of the microfluidic cassette that improved the ease-of-use of the device and shortened the time-to-result. We implemented this new cassette to create a rapid diagnostic test to detect talaromycosis infection in patients with advanced HIV disease at the POC, demonstrating comparable sensitivity and specificity to the laboratory test for the disease.

Automated summary

We developed a self-contained immunoassay platform that can be used in field settings with varied temperature, humidity, and blood samples. The platform has high sensitivity and accuracy in detecting analyte concentration, and a portable detection device. We also improved the microfluidic cassette for better usability and faster results. By using this platform, we successfully conducted a rapid diagnostic test for talaromycosis infection in patients, showing comparable sensitivity and specificity to laboratory tests.