Polymerase chain reaction definition

Laboratory confirmation is vital to effective treatment of HSV, especially in individuals in whom a clinical diagnosis cannot be obtained. There are several methods by which a definitive diagnosis may be acquired, and these include virologic typing, serologic diagnosis, rapid point-of-care antigen detection, enzyme-linked immunosorbent assay (ELISA), immunoblot, and DNA polymerase chain reaction.27... 

CDC Case Definition An illness with acute onset of fever >101°F followed by a rash characterized by firm, deep seated vesicles or pustules in the same stage of development without other apparent cause. Clinically consistent cases are those presentations of smallpox that do not meet this classical clinical case definition (1) hemorrhagic type, (2) flat type, and (3) variola sine eruptione. Laboratory criteria for diagnosis is (1) polymerase chain reaction (PCR) identification of variola DNA in a clinical specimen, or (2) isolation of smallpox (variola) virus from a clinical specimen (Level D laboratory only confirmed by variola PCR). 

Short tandem repeat (STR) or microsatellite loci consist of DNA sequence motifs that have core repeats of two to seven base pairs. Examples include the dinucleotide 5 CACACACA 3 and the tetranucleotide 5 TTTATTTATTTA 3". Thousands of STRs are scattered throughout the genome. Because they are flanked by unique sequences, each can be specifically amplified with the polymerase chain reaction (PGR) for analysis. In populations of individuals, multiple alleles may be present based on differences in the number of repeated motifs at the locus. STRs have many characteristics that make them ideal for identity testing (1) They can be analyzed in fluorescent automated systems (2) alleles can be assigned in a definitive manner following analysis (3) STR loci are almost always transmitted in families in a Mendelian fashion (4) the loci may have 10 or more alleles, often with... 

The polymerase chain reaction can increase the amount of a desired DNA sample by a considerable factor, making possible definite identification of DNA samples that were too small to be characterized by other means. It can be used on hair and blood samples found at the scene of a crime to establish the presence of a suspect. This method can also be used to identify remains of possible murder victims. 

Even these brief comments on causality clearly indicate that one agent one disease is far too simplistic and pathogen identification is definitely not the same as diagnosis. However, there are many examples of people still proposing techniques such as polymerase chain reaction (PCR) for initial diagnosis. Although such pathogen identification techniques have a role in research and surveillance (and other areas), they very rarely, if ever, confirm the infectious cause of a disease and never provide any information on the rest of the causal web. 

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