Diagnostic testing
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Diagnostic Testing. Noelle Lewis Molecular Biology. Principles of Genetic testing. A genetic diagnostic test identifies a specific indicator that shows whether a person will have or develop a disorder Positive test results indicate a person has the indicator

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Diagnostic Testing

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Diagnostic testing

Diagnostic Testing

Noelle Lewis

Molecular Biology


Principles of genetic testing

Principles of Genetic testing

  • A genetic diagnostic test identifies a specific indicator that shows whether a person will have or develop a disorder

  • Positive test results indicate a person has the indicator

  • Negative test results indicate the indicator is absent


Principles of genetic testing1

Principles of Genetic testing

  • False positives and negatives are common

  • A false positive could result in a person having unnecessary anxiety and often unnecessary treatment

  • A false negative could result in the person thinking they do not have the disease when they actually do

  • Clinical tests are adjusted to minimize the occurrence of false results


Principles of genetic testing2

Principles of Genetic testing

  • Sensitivity and specificity are used to judge the clinical validity of a test

  • Sensitivity is the fraction of correctly identified people who truly have the indicator- TP

    TP+FN

    Specificity is the fraction of people who do not have the indicator- TN

    TN+FP

    A condition is likely present when a test is positive and specificity is high.


Testing for genetic disorders

Testing for genetic disorders

  • A test used to identify an inherited disorder

  • The indicator may be a chromosome, protein, metabolite, or nucleic acid sequence

  • Chromosome abnormalities are detected by karyotype staining or fluorescent in situ hybridization (FISH).

  • Biochemical and immunological assays of blood and urine test amino acids, organic acids, and metabolites or proteins

    -The Guthrie test-Phenylketonuria in infants


Genetic testing

Genetic testing

  • Accumulation or deficiency of a metabolit can be detected by tandem mass spectromery

    • The m/z pofile is compared to known standards to identify and quantify the indicator

    • Tandem MS is efficient and can detect and measure the amounts of many different indicators


Genetic testing1

Genetic testing

  • Other methods include assays that use the known human genetic sequence to identify mutations, single-strand conformation polymorphism, denaturing gradient gel electrophoresis, and denaturing high-performance liquid chromatography


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