Lateral flow assays, also known as immunochromatographic assays, are low-cost, user-friendly, portable devices that are important tools for the detection of target analytes, such as pathogens and biomarkers. Lateral flow assays offer high sensitivity and selectivity using labelled reporter particles that recognize and bind the analyte. Larger analytes are generally tested by sandwich assays, in which the target analyte conjugates a specific antibody labelled with a visual tag, typically colloidal gold. The bound antibody and target analyte migrate together to the test line where a visual change is detected when sufficient analyte is present. A control line should also undergo a chromatic change if the lateral flow pad is functioning properly.