PCR-By amplification of the DNA of vims or bacteria present in the patient helps to identify even the concentration of pathogen is very low in the body of the patient.
A single stranded DNA or RNA is tagged with a radio active molecule (probe) is allow to hybridized to its complementary DNA in clone of cells followed by detection using autoradiography. Thus the mutated gene can be detected as it will not hybridize with the probe.
ELISA – Enzyme linked immuno- sorbent assay is based on the principle of antigen antibody reaction. Infection by pathogen is an antigen it can be detected by the presence of antibodies synthesized against it.