 # What Does It Mean If A Test Is Sensitive But Not Specific?

## What does sensitivity and specificity of a test mean?

In medical diagnosis, test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate)..

## Why is the sensitivity and specificity of a test important in relation to diagnosis?

The advantages of using sensitivity and specificity in the evaluation of diagnostic tests. Statistically, the advantages of using sensitivity and specificity are: They do not alter if the prevalence changes between populations (see predictive values) They can be applied in different populations.

## Is specificity more important than sensitivity?

A highly sensitive test means that there are few false negative results, and thus fewer cases of disease are missed. The specificity of a test is its ability to designate an individual who does not have a disease as negative. A highly specific test means that there are few false positive results.

## How do you read sensitivity and specificity results?

The sensitivity of the test reflects the probability that the screening test will be positive among those who are diseased. In contrast, the specificity of the test reflects the probability that the screening test will be negative among those who, in fact, do not have the disease.

## Why diagnostic tests are not perfect?

However, as very few tests are perfect, often an imperfect reference is used. Furthermore, due to several biases and sources of variation, such as differences in case mix, and disease severity, the measures of accuracy cannot be considered as fixed properties of a diagnostic test.

## What is sensitivity of a test?

What do sensitivity values tell you? The sensitivity of a test is also called the true positive rate (TPR) and is the proportion of samples that are genuinely positive that give a positive result using the test in question. For example, a test that correctly identifies all positive samples in a panel is very sensitive.

## What is positive predictive power?

Definition. Positive predictive value (PPV) represents the probability that a person has a disease or condition given a positive test result. … PPV is related to the sensitivity and specificity of the test. Sensitivity refers to the true positive rate for people with a disease or condition having a positive test result.

## What is the difference between specificity and sensitivity in an immunoassay?

SENSITIVITY is the proportion of true-positives which actually test positive, and how well a test is able to detect positive individuals in a population. … SPECIFICITY is the proportion of true-negatives which actually test negative, and reflects how well an assay performs in a group of disease negative individuals.

## What is true positive and true negative?

A true positive is an outcome where the model correctly predicts the positive class. Similarly, a true negative is an outcome where the model correctly predicts the negative class. … And a false negative is an outcome where the model incorrectly predicts the negative class.

## What is specificity of a diagnostic test?

The specificity of a test is defined in a variety of ways, typically such as specificity being the ability of a screening test to detect a true negative, being based on the true negative rate, correctly identifying people who do not have a condition, or, if 100%, identifying all patients who do not have the condition …

## What effect will increasing sensitivity have on specificity?

Specificity (negative in health) = Probability of being test negative when disease absent. 85 / 100 = 85%. Sensitivity and specificity are inversely proportional, meaning that as the sensitivity increases, the specificity decreases and vice versa.

## How is sensitivity calculated?

Sensitivity=[a/(a+c)]×100Specificity=[d/(b+d)]×100Positive predictive value(PPV)=[a/(a+b)]×100Negative predictive value(NPV)=[d/(c+d)]×100.

## How do you calculate a false positive?

The false positive rate is calculated as FP/FP+TN, where FP is the number of false positives and TN is the number of true negatives (FP+TN being the total number of negatives). It’s the probability that a false alarm will be raised: that a positive result will be given when the true value is negative.

## Should a screening test be sensitive or specific?

Test Validity. Test validity is the ability of a screening test to accurately identify diseased and non-disease individuals. An ideal screening test is exquisitely sensitive (high probability of detecting disease) and extremely specific (high probability that those without the disease will screen negative).

## When would you prefer a diagnostic test with high sensitivity?

A test with 80% sensitivity detects 80% of patients with the disease (true positives) but 20% with the disease go undetected (false negatives). A high sensitivity is clearly important where the test is used to identify a serious but treatable disease (e.g. cervical cancer).

## What sensitivity and specificity is acceptable?

Generally speaking, “a test with a sensitivity and specificity of around 90% would be considered to have good diagnostic performance—nuclear cardiac stress tests can perform at this level,” Hoffman said. But just as important as the numbers, it’s crucial to consider what kind of patients the test is being applied to.

## Is positive predictive value the same as sensitivity?

The Positive Predictive Value definition is similar to the sensitivity of a test and the two are often confused. However, PPV is useful for the patient, while sensitivity is more useful for the physician. Positive predictive value will tell you the odds of you having a disease if you have a positive result.

## How is screen sensitivity test calculated?

Sensitivity is the probability that a test will indicate ‘disease’ among those with the disease:Sensitivity: A/(A+C) × 100.Specificity: D/(D+B) × 100.Positive Predictive Value: A/(A+B) × 100.Negative Predictive Value: D/(D+C) × 100.