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Molecular Diagnostics

Introduction

Molecular diagnostics are the tests that a physician orders from a lab to detect biomarkers that provide information about an individual patient’s health condition. In personalized medicine, physicians and patients use the results of the tests to help decide on therapies and preventive measures.

As indicated by the graphic below, there are more than 60,000 genetic tests on the market today. These tests are just one kind of molecular diagnostic. Click on the graphic for more information about genetic tests.

How Many Genetic Testing Products Are There?


Source: NextGxDx. Published with permission from NextGxDx.

Validity & Utility: The value of molecular diagnostics in accurately helping to determine optimal treatment strategies is based on the validity and utility of a test. Validity and utility provide a framework for interpretation of the evidence regarding the accuracy and usefulness of the information the test provides.

Analytical Validity

Analytical validity refers to how well a diagnostic test measures the characteristics of the particular biological marker that it is intended to measure (i.e. how accurately does it measure the presence of X or Y molecule in a patient).

Analytical validity is governed by sensitivity and specificity.

Sensitivity: The frequency with which a test correctly identifies the presence of a biomarker. When this happens, the test is said to have yielded a "true-positive" result. When the test indicates the absence of a biomarker that is actually present, it is said to have yielded a "false-negative" result. A test with 95 percent sensitivity, for example, correctly identifies people with the biomarker 95 percent of the time, and thus has a low "false-negative" rate.

Specificity: The frequency with which a test correctly identifies the absence of a biomarker. When this happens, the test is said to have yielded a "true-negative" result. When the test indicates the presence of a biomarker that is actually absent, it is said to have yielded a "false-positive" result. A test with 95 percent specificity, for example, correctly identifies people without the biomarker of interest 95 percent of the time, and thus has a low "false-positive" rate.

Clinical Validity

Clinical validity refers to the predictive value of a test for indicating an association between an analytic endpoint and a clinical outcome (e.g., the likelihood that cancer will develop in someone with a positive test).

Clinical Utility

Clinical utility refers to the likelihood that the test will, by prompting an intervention, result in an improved health outcome. The clinical utility of a genetic test is based on the health benefits related to the interventions offered to people with positive test results.

The clinical utility of a test is largely based on its ability to improve safety, efficacy and effectiveness.

Safety: The capacity to reduce adverse treatment effects.

Efficacy: The capacity to produce an improved health outcome.

Effectiveness: The likelihood that the improved outcome will occur, taking into account actual use of the intervention and recommended follow-up.