<s>[INST] context: (PCR) (948 - 52 Davidson 21st) (2540-50-H1 8th)Tests used for screaming hepatitis B are estimation of surface antigen (HBSAg) anti HBc and anti HBS antibodies.Which people should be screened for hepatitis B.* Hemodialysis patients* Pregnant women* Infants bom mother who are HBSAg positive* Person known or suspected of having bean exposed to HBV - donors of blood, organ and tissue.* People bom in areas where HBSAg prevalence in found to be equal to or more than 2%.* Men who have had sex with man* Drug addicts using injectable drugs HIV positive individuals.* Patients likely to take immunosuppressive treatment or cancer chemotherapy.* Patients with increase liver enzyme of undetermined cause.The tests, called assays, for detection of hepatitis B virus infection involve serum or blood tests that detect either viral antigens (proteins produced by the virus) or antibodies produced by the host. Interpretation of these assays is complex.The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection.PCR tests have been developed to detect and measure the amount of HBV DNA, called the viral load, in clinical specimens. These tests are used to assess a person's infection status and to monitor treatment. Individuals with high viral loads, characteristically have ground glass hepatocytes on biopsy.For infections caused by agents such as Hepatitis C virus (HCV), Hepatitis B virus (HBV), Human Immunodeficiency virus (HIV) or other agents both viral or bacterial origin, commonly used tests determine the presence of specific antibodies produced by the patient's immune system in response to infectious agent.New generation of tests has been developed, which are based on measuring the presence of the infectious agent within the patient sample directly. These tests detect the presence of nucleic acids (the genetic material) of the infections agents in the blood or other samples from the patient. The most common is the Polymerase Chain Reaction (PCR) which can detect 100 copies or more of an infectious agent in a single sample. PCR uses an enzymatic reaction to amplify specific nucleic acid sequences from the infectious agent if they are present in the sample. There are several problems with this method. PCR uses specific nucleic acid sequences (Primers) from an already known sequence of the infectious agent. Therefore, if the infectious agent has not been sequenced, PCR can not be used. Similarly, if the infectious agent mutates very rapidly, the Primers may not recognize the infectious agent and a false negative test will result... Another is a hybridization method where the amplified product is detected by hybridization to an infectious agent specific probe.The second method is based on direct hybridization of the infectious agent's nucleic acid to a synthetic nucleic acid probe. The hybridized infectious agent is then detected by amplifications using non-enzymatic methods.The major drawback of this method is that it is less sensitive (minimum 1,000 copies must be present in a sample) and requires a larger amount of the patient's sample (minimum 1 ml blood compared with 0.1 ml for PCR).Microchip assayThere is a need for a sensitive and rapid assay, which is easy to perform, can be used in laboratories with very little experience or no experience in molecular biological methods. The 'first generation' diagnostic microarray developed can detect thirteen infectious agents simultaneously, and can be expanded do detect several hundreds, and reduces the detection time to less than 30 minutes. Because it is based on a rapid hybridization and no enzymatic amplification is used, it is not affected by impurities in the sample. It can be adapted to any type of sample such as blood, stool or tissues. The size of the chip is less than one cm2and the active site is less than 1 mm2. [/INST] question: For screening of hepatitis-B, most commonly used test is - | options: A: Microtitre assay B: RIA C: Double diffusion D: PCR | answer: D </s>