Everyone knows the relief that comes with a negative test result, and those same people can imagine the fear and dread that comes with a positive one.
But some people will have an effect that doesn’t cause fear or relief – it just leaves them scratching their heads.
Inconclusive results are unusual, but they do happen. Keep reading to find out what it is, why it happens, and what to do if you get it.
It is important to know the state of your sexual health.
How do STD tests work?
To understand what unclear test results can mean, we need to understand how STD tests work.
Like many medical tests, STD tests use samples—a representative piece of a problem area—to determine if an infection is present. These samples usually have the form blood, urineor swabs.
- Blood samples are collected from your vein using a needle. This can be done in a clinic by a nurse or at home using a finger lancet.
- Urine samples collected in containers, either at the clinic or at home. They are usually collected by the patient in both cases.
- Smear samples collected using a swab to collect a small amount of material from the affected area – usually the genitals, mouth or rectum.
These samples are then processed using a variety of test methods such as polymerase chain reaction (PCR), antibody test and antigen, depending on the infection being tested.
- PCR tests detects the DNA of specific pathogens in a sample.
- Antibody tests identify the antibodies your body makes to fight certain infections. Antibody tests are usually done for viral infections such as HIV and Hepatitis B.
- Antigen tests detection of antigens produced by viruses. Antigen tests can help detect some infections in the early stages.
There are four possible outcomes in a test: positive, negative, inconclusiveand ambiguous. You probably know what positive and negative mean. But what about the other two?
What does an unclear test result mean?
“Inconclusive” means that the test in question was performed correctly – there is no problem with the equipment – but the laboratory was unable to make a reliable determination, either positive or negative. In other words, the sample did not give a definitive result one way or the other.
What does an ambiguous test result mean?
A “questionable” test result is similar to an unclear test result. However, it means something a little more specific: that the results fall within a marginal range – too low to be considered positive, but too high to be considered negative. This type of result is more common with antibody tests.
Why would you get these results?
An unclear or ambiguous test result can be caused by a number of factors.
Sample issues
Sometimes, a sample is not optimal. If the sample provided is not viable, the test will not be able to detect infection.
Some common sampling issues include:
- Insufficient sampling: The amount of blood or urine supplied did not meet the required limit.
- Relegation: Too much time has passed since the sample was taken. This is usually caused by late transfer.
- Contamination: Foreign substances have contaminated the sample, making it unfit for testing.
- Inappropriate collection: Issues during collection may compromise sample viability.
Incorrect sample timing or early stage of a condition
For an infection to reach a detectable level in your body, samples must be taken at the right time.
For most STD tests, 14 days after the worrying event should be enough. However, a longer period (a few more days to several weeks) could provide a more robust and reliable sample.
For example, it is quite common for people infected with HIV to be tested too early. The urgent need for clarity about their condition may force some people to undergo testing before the appropriate amount of antigens or antibodies have developed. Someone who is tested too early may have a negative result but still be infected.
If you are having a test, pay attention to the clinical guidance on the timing of the test.
Biological variation
In the antibody test, some people naturally produce marginal or fluctuating levels of antibodies, and the immune response may vary from patient to patient. In other words, some people may produce more antibodies than others in response to the same infection. This can make determining the critical levels of said antibodies a bit difficult in some cases.
Medicines and supplements
While most tests are not affected by drugs or supplements, excessive consumption of biotins (vitamin B7 or B8, vitamin H or coenzyme R) should be avoided in the days before the test.
Other immunoassays for hormone testing can also be affected by substances such as dopamine, fluorescein, and prednisone.
Consult your doctor before having a test if you are taking any medications or supplements.
Technical factors
These are laboratory- and instrument-related factors that can confound accurate detection.
- Low level signal interference: Interference refers to substances or conditions that disrupt the test’s ability to accurately detect the pathogen signal. These may include sample contamination from powders or detergents, as well as matrix effects, where the physical composition of a sample affects signal production.
- Marginal analysis performance: Tests are designed with defined limits. Marginal performance can occur when small fluctuations push results into a “grey area”
- Instrument Variability: Faulty equipment, unstable temperature control, or inconsistent reagent quality can all make a result unreliable.
- Procedural errors: Sometimes, errors occur that result from sample handling and testing – pipetting errors, mislabeling, and deviations from protocols can affect assay performance.
Diet and lifestyle
Certain diet and lifestyle factors can affect test results.
- Non-fasting: Eating before a test that requires fasting can change your blood sugar and lipid levels.
- Physical activity: Vigorous exercise before an exam can elevate certain muscle enzymes.
- Time of day: Levels of certain hormones, such as cortisol, fluctuate throughout the day based on your circadian rhythm. The timing of the test can be critical.
- Menstrual cycle: When you are tested during your cycle, the results can be skewed into uncertain territory.
Other conditions
Cross-reactivity between antibodies and a different, related virus (eg, a common cold) can cause an ambiguous result in an antibody test.
Individual biological variability
Some people have natural levels of certain biomarkers that are outside of the “normal” range, but are normal for them, which may be flagged as a spurious result.
What should you do if you get these results?
Getting one of these results can be confusing. Here’s what we recommend to all our patients who have an unclear or ambiguous result.
Repeat the test
Re-examination is the first step. This can provide clarity, especially if there were problems with the sample collected.
Following clinical guidelines
When you get an inconclusive result, subsequent tests should be conducted using the correct procedures and methods. Patients undergoing screening should follow clinical guidelines, especially when collecting samples after the appropriate incubation period.
Consider the clinical context
Symptoms, exposure history, or other relevant information may guide next steps along with retesting.
Final thoughts
Getting any test result other than negative can be very stressful. But it is important not to panic. Remember that most STDs are curable and most others can be managed with proper care and medication.
Book an STD test near you by clicking the button below. You can also speak to a member of our friendly Patient Services team. They can talk to you about your condition and even book a test for you.
Don’t leave your sexual health to chance.
