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What Are Pathologic Diagnostic Techniques?

Pathology is defined as "the science of the causes and effects of diseases, especially the branch of medicine that deals with the laboratory examination of samples of body tissue for diagnostic or forensic purposes." Pathology uses many techniques to examine abnormal tissues or bodily fluids and compares them to normal values. This allows the pathologist to diagnose and treat the disease or symptom present.

  1. Working with DNA

    • PCR, or polymerase chain reaction, is the most common technique used in diagnostic laboratories. This technique makes 30 to 40 copies of selected DNA and tracks the behavior of the DNA using fluorescent dyes and computer programs. A recent innovation called Real Time PCR allows the DNA to be examined as it is copied and created. This allows for more rapid results and effective treatments especially when it comes to cancers and leukemia.

    FISHing

    • FISH, or fluorescent in situ hybridization, is another diagnostic technique using fluorescent dyes and microscopes. This technique uses genes to attach to specific portions of the DNA in a cell. Normal cells have a one-to-one ratio of colors. Abnormal cells fall in the range of two-to-one ratios or greater. This technique is advantageous as it can be used on tissue that is at rest or has been in lengthy transit to the lab. As with PCR, it provides rapid results for diagnosis and treatment of abnormalities.

    Painting Chromosomes

    • Spectral karyotype imaging, or SKI, involves the painting of chromosomes with varying amounts of three different fluorescent dyes. The amount of dye in each chromosome shows up as a different color often undetectable by the human eye. A computer translates this information into a map of chromosome colors. A pathologist can then see numeric abnormalities in the cells or shifting of colors allowing for the diagnosis of specific diseases or conditions.

    Gene Expressions

    • A strand of cellular DNA

      Two other types of DNA microarrays show great potential in diagnostics. They are cDNA microarrays and oligonucleotide/DNA chips. Fluorescence is used to detect the expression or strength of a gene at a DNA location. The color of the florescence tells the pathologist whether the gene is overexpressing (overactive) or underexpressing (not active enough). This can reveal a great deal to him about the sample he is analyzing. This method has the advantage of analyzing a great deal of tissue or genetic material in a single test.

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