These tests are based on the principle of Immuno-Diffusion. These assays include so called "Dipsticks" and "Combs". These are particularly suited for semi quantitative analysis. Dipstick uses Nitrocellulose membrane and is most commonly used for protein spots. There can be one or more pads in the same dipstick. Comb has 8 or 12 legs which fits into a normal ELISA plate and allows multiple samples to be tested at the same time. An advantage of these tests is that they allow individual patients to be tested for one or multiple parameters with a single assay.