Specificity & sensitivity

How reliable is a test result? Concepts such as sensitivity and specificity determine how well a test performs. We explain what they mean and how Homed-IQ handles them.

Sensitivity

Describes how well a test can detect a condition when it is actually present.

A highly sensitive test correctly identifies most people who have the condition (few false-negative results).

In practice: if your result is negative, you can be highly confident that you do not have the condition.

Specificity

Describes how well a test can confirm that a condition is not present.

A highly specific test correctly identifies most people who do not have the condition (few false-positive results).

In practice: if your result is positive, there is a high probability that it is genuinely correct and not a false alarm.

Good to know

Tests with both 100% sensitivity and specificity are extremely rare. Most diagnostic tests, including those used in hospitals, do not achieve these values. Homed-IQ selects tests with high sensitivity and specificity, comparable to the tests used in clinical settings.

Test performance of Homed-IQ STI tests

Sensitivity and specificity can only be calculated for tests that directly diagnose a condition. For tests that measure blood values (such as vitamins or cholesterol), these statistics do not apply, as there is no universal threshold that clearly separates "affected" from "not affected".

Marker	Sensitivity	Specificity
Chlamydia	98.2%	99.8%
Gonorrhoea	97.7%	99.8%
Mycoplasma genitalium	95.8%	98.9%
Syphilis	100%	99.88%
Hepatitis B	99.9%	99.9%
HIV	100%	99.90%

Why both matter together

Sensitivity and specificity should always be considered together. A test that is highly sensitive but less specific will miss few infections but may produce more false-positive results. Conversely, a highly specific but less sensitive test will produce few false positives but may miss some cases.

Screening tests are often highly sensitive, so that as few cases as possible are missed.

Confirmatory tests are often highly specific, so that a positive result is as reliable as possible.

What does this mean for you?

Negative result

With a test that has high sensitivity, this provides a high degree of certainty that you do not have the tested condition.

Positive result

With a test that has high specificity, there is a high probability that the result is genuinely correct and not a false alarm.

With every result

Homed-IQ results always include clear reference values, an interpretation of the result and advice on next steps where needed.

The sensitivity and specificity of a test are determined by the analysis method used, the quality of the laboratory and the validation of the test. The location of sample collection (at home or in a clinic) does not change these properties, provided three conditions are met:

Because Homed-IQ works with ISO 15189 and DAkkS-accredited laboratories, the test performance is comparable to clinical diagnostics. The reliability of your result is equivalent to what you would receive at your GP or in hospital.

Transparency about test performance

Homed-IQ publishes sensitivity and specificity where this is scientifically possible and relevant. This aligns with our commitment to:

Transparency Medical reliability Understandable diagnostics

This way you know exactly what a test can and cannot detect, and you can determine the right next steps together with your GP or healthcare provider.

Frequently asked questions

Which is more important: sensitivity or specificity?

Neither is more important by definition, it depends on what the test is used for. For infections such as HIV or chlamydia, high sensitivity matters most, because missing an infection has bigger consequences than a false alarm. Specificity becomes more important when a positive result leads to invasive follow-up or treatment. Screening tests are therefore usually designed for high sensitivity, with a confirmatory test to catch the rare false positive. Homed-IQ selects tests that score high on both.

Can a test with high sensitivity still be wrong?

Yes. Sensitivity says something about the test itself under ideal conditions, not about the moment you take it. The most common reason for an incorrect result is testing too early: within the window period there is not yet enough antibody or genetic material present to detect. Sample quality plays a role too, for example too little blood or a swab that was not collected according to the instructions. This is why we state a window period for every test and why we advise always discussing a positive result with a doctor.

Does 100% sensitivity mean a test is always correct?

No. 100% sensitivity means that in the validation study the test identified every sample that contained the marker. It says nothing about false positives, that is specificity. Such a study also takes place under controlled laboratory conditions, using samples collected at the right moment. In practice, timing and sample quality affect the outcome as well, so no test is correct in 100% of cases.

Why do not all tests have sensitivity and specificity values?

Because those values only apply to tests with a yes or no outcome, such as an STI test. Tests that measure a level in your blood, like vitamin D, cholesterol or TSH, do not produce a diagnosis but a value that is compared to a reference range. There is no single threshold separating "disease" from "no disease", so sensitivity and specificity cannot be calculated. The quality of these tests is expressed differently, among other things in trueness and precision compared to the laboratory's reference method.

How reliable are home tests compared to hospital tests?

The analysis is identical: your sample is analysed in an ISO-certified laboratory using the same equipment and methods as samples collected by a doctor. The difference is in the collection, which you carry out yourself instead of a healthcare professional. That is why Homed-IQ only uses collection materials validated for self-collection, and why detailed instructions are included with every test. Research into self-collected samples for STI testing shows results comparable to clinically collected samples.