True Negative Tn
- A True Negative (TN) is a negative diagnostic test result that correctly reflects that the individual does not have the condition.
- TN contrasts with a False Negative (FN), where the test incorrectly reports absence despite the condition being present.
- TN results support accurate diagnosis and appropriate care; False Negatives can delay diagnosis and treatment.
Definition
Section titled “Definition”True Negative (TN) is a term used in medical testing and diagnosis to describe a test result that accurately indicates the absence of a particular condition or disease.
Explanation
Section titled “Explanation”A TN result is a negative test outcome that matches the individual’s true health status — the condition being tested for is not present. TN results are important because they contribute to correct diagnosis and appropriate follow-up care. By contrast, False Negative (FN) results occur when a test reports a negative outcome even though the condition is present; such FN results can be harmful by delaying diagnosis and treatment.
Examples
Section titled “Examples”Example 1: HIV testing
Section titled “Example 1: HIV testing”Imagine a person undergoes an HIV test to determine if they are infected with the HIV virus. If the test result is negative, it means that the person does not have HIV. However, this result can either be a TN or a False Negative (FN). A TN result would mean that the person truly does not have HIV, whereas an FN result would mean that the person does have HIV but the test wrongly indicated a negative result.
To understand the difference between TN and FN, consider the following scenarios:
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A person gets tested for HIV after engaging in risky behavior (such as unprotected sex or sharing needles). The test result comes back negative. In this case, the result is a TN because the person truly does not have HIV and the test correctly reflected that.
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Another person gets tested for HIV after engaging in risky behavior but this time the test result comes back positive. If further testing (such as a Western Blot test) confirms that the person is indeed HIV positive, then the initial test result was a TN because it accurately indicated the presence of HIV.
Example 2: Breast cancer screening
Section titled “Example 2: Breast cancer screening”Breast cancer screening detects breast cancer at an early stage, often before symptoms appear. Mammography is a common screening method that uses x-rays to image breast tissue.
If a person undergoes mammography and the test result is negative, it means that the person does not have breast cancer. That negative result can be either a TN or a False Negative (FN). A TN result indicates the person truly does not have breast cancer; an FN indicates the person does have breast cancer but the test missed it.
To illustrate:
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A woman undergoes mammography as part of her regular breast cancer screening. The test result comes back negative. In this case, the result is a TN because the woman truly does not have breast cancer and the test correctly reflected that.
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Another woman undergoes mammography as part of her regular screening and the test result comes back positive. If further testing (such as a biopsy) confirms that the woman does indeed have breast cancer, then the initial mammography result was a TN because it accurately indicated the presence of breast cancer.
Notes or pitfalls
Section titled “Notes or pitfalls”- False Negative (FN) results can be harmful because they may lead to a delay in diagnosis and treatment.
Related terms
Section titled “Related terms”- False Negative (FN)
- Western Blot
- Biopsy