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Diagnostic Testing

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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  1. Diagnostic Testing Noelle Lewis Molecular Biology

  2. 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

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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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