Analytical Validity: Does the Test Measure What It Says?

What the term means

MedlinePlus Genetics, a U.S. National Library of Medicine resource, describes analytical validity for genetic tests as how well a test predicts the presence or absence of a particular gene or genetic change. [1] In plain words: if a variant is really there, does the test find it, and if it is not there, does the test stay quiet? The same idea applies to blood, urine and other laboratory tests. Does a cholesterol test report the amount of cholesterol actually in the sample?

One older framework for imaging describes a ladder of questions. Level 1 is the technical quality of the images, and level 2 is diagnostic accuracy. Proving the lower levels is necessary but not enough to show benefit at the higher levels. [2] Analytical validity sits near the bottom of that kind of ladder. A test can pass it and still be useless for a given purpose.

What can go wrong in the laboratory

• Method differences. MedlinePlus notes that labs often use different testing methods and reference ranges, so results from different labs cannot be compared directly. [3]
• Preparation and timing. Foods and drinks, medicines or supplements, hard exercise, a menstrual period and whether preparation instructions such as fasting were followed can all affect some results. [3]
• Mistakes. Incorrect results are uncommon but more likely with certain test types or if testing was not done correctly. [3]
• Sample handling. A large hospital study of about 9.8 million results found that being fasted for under 8 hours was linked to higher glucose, triglycerides, gamma-glutamyl transferase and lipase. Across 372 test items, fasting differences exceeded accepted performance limits for only a few, and the authors concluded that fasting needs differ by test. [4] This was one hospital in Korea, and it was an observational study.

How tests are checked, and by whom

In the United States, laboratories doing health-related testing fall under federal standards called the Clinical Laboratory Improvement Amendments (CLIA). Those standards cover how tests are performed, staff qualifications and quality control. They are designed to support analytical validity but do not address clinical validity or clinical utility. [1]

The FDA separately reviews many test kits as medical devices. Laboratory-developed tests, made and used inside a single lab, have a more changeable history. According to the FDA's page, a May 2024 final rule that would have brought them under device rules was vacated by a federal court on March 31, 2025, and on September 19, 2025 the FDA reverted the regulation's text to its earlier form. [5] Rules may have changed since this was read on 2026-10-22, and this is not legal advice.

Direct-to-consumer genetic tests can be harder to judge. MedlinePlus says some providers are not CLIA-certified and many such tests are not FDA-regulated, so it can be difficult to tell whether they are valid. [1] See direct-to-consumer genetic tests.

How a new test is compared with an old one

When a test is evaluated against a method that is not a true reference standard, the FDA's statistical guidance says it is not possible to calculate unbiased estimates of sensitivity and specificity. [6] The guidance also stresses that "agreement" does not mean "correct", because two tests can agree and both be wrong. [6] A claim that a test "matches the lab standard" therefore needs a look at what it was matched against.

Questions worth asking about any test

• What exactly does it measure, and in what sample (blood, saliva, stool, hair)?
• Which laboratory ran it, and is that lab subject to quality standards where you live?
• Was it checked against a reference method, and was that published?
• Were instructions for preparation followed?

Good answers to these only show the test is technically sound. For what a result means, see sensitivity, specificity and predictive values and the practical guide to biomarker tracking and at-home tests.