Three types of PoC diagnostic tests.
A biological sample (such as blood, urine, saliva, sweat, etc.) can be utilized for various types of PoC diagnosis. Left: immunological PoC test. A biological sample is dropped unto the sample pad of a lateral flow assay, which acts as a filtering unit to sieve out unnecessary constituents. Upon administration of a reaction buffer (or its automated release), the analyte flows through the reagent pad, wherein an antigen–antibody complex is formed. Driven by capillary action, this complex migrates to the next zone with control and test lines. While the appearance of a visible color at the test line confirms the infection, the control line signal ensures the test functionality. Middle: nucleic acid–based PoC test. Here, genetic material of a pathogen serves as the analyte. DNA/RNA from the pathogen is extracted from infected host cells or circulating cell free within the clinical sample (body fluids). While extracted RNA is first reverse transcribed to obtain cDNA, extracted DNA can be directly amplified using PCR or using isothermal amplification (e.g., RPA or LAMP), typically in a fully automated portable unit. In some systems, the amplified DNA is then used for CRISPR/Cas recognition or other downstream processing to yield a diagnostic result within a lateral flow assay or a microfluidic lab-on-a-chip device. NGS can also be utilized to identify specific diseases using a portable sequencer. Right: biomarker-based PoC test (other than antigen biomarkers). A biological sample is administered onto the test pad that in this case has specific surface-bound molecules such as aptamers that target the analyte. Upon successful interactions, a visible color readout is obtained. The test can be in the form of separate wells. LAMP, loop-mediated isothermal amplification; NGS, next-generation sequencing; PCR, polymerase chain reaction; PoC, point-of-care; RPA, recombinase polymerase amplification.