Diagnosis On-Demand: Field Evaluation of Microfluidic Paper Device for the Detection of Asymptomatic Malaria.

We report a proof-of-concept surveillance strategy that combines simplicity with modest cost to achieve high analytical performance for the detection of asymptomatic malaria infection. We developed a microfluidic paper-based analytical device (μPAD) that automates immunoassay using 30 μL of whole blood. A novel dendrimer-based signal transduction method was introduced to amplify the mass spectrometry (MS) signal. Our ability to detect an immunoassay signal with MS was achieved using cleavable ionic probes that were attached to monoclonal antibodies via dendrimer bioconjugation. The limit of detection of this MS-based immunoassay was determined to be 4.5 pM in serum for Plasmodium falciparum histidine-rich protein 2. The high stability of the ionic probes allowed storage of the paper device at room temperature, facilitating field sampling of whole blood from 266 asymptomatic volunteers in Ghana. The performance of the μPAD platform was compared with polymerase chain reaction (PCR), light microscopy, and rapid diagnostic test (RDT). Using PCR as the reference, we observed 96.5% sensitivity for our μPAD platform, as opposed to 43% for RDT and 16.9% for microscopy. Cohen's Kappa statistical analysis confirmed almost perfect agreement between μPAD and PCR (%agree = 81% in Kappa's categorical terms). False-negative rate in μPAD was calculated to be 3.5%. These results highlight the need for a more sensitive tool for asymptomatic malaria screening. Our method is highly sensitive yet deliverable, making sustainable implementation possible in underserved communities.