False Positive Vs False Negative Test
01 March 2021
STD tests offer a high degree of accuracy if completed correctly, but there are a number of situations which might lead to an inaccurate result. This is known as either a false negative or a false positive result. In this blog, we take a look at these two outcomes, what might cause them and analyse the difference between the two.
Effects Of Std Window Period On Test Results
If you have a negative STD test, but youre still worried, the cause of your negative result is most likely due to the window period. The STD window period is the amount of time it takes for an STD to register on a test. What does this mean, and how can it affect your STD test results?
If youre exposed to an STD and end up catching it, you wont test positive right away. That can have some significant side effects on your sexual health. For example, if you get tested within the window period and receive a false negative, you could transmit the disease to sexual partners.
Another dangerous effect of getting tested too soon during the window period is delaying treatment. If you dont receive treatment for an STD, it can cause adverse effects on your health and well-being.
Here are thewindow periods for the most common STDs:
- HIV: Between 10 and 90 days
- Chlamydia: one to two weeks
- Syphilis: one to three weeks
- Hepatitis: Between two and six weeks
- Gonorrhea: five to 14 days
- HPV: three weeks to about three months
- Trichomoniasis: one week to 30 days
- Herpes: one to four months
As you can see, its essential to get regular STD tests since the window period can have such significant effects on your results.
My Test Result Is Reactive Whats The Chance That This Is A False Positive
If you tested in a healthcare facility, the staff there should make sure you have the necessary follow-up tests. This sequence of confirmatory tests is carefully planned to prevent inaccurate results from being given. Healthcare professionals call it a testing algorithm. If you have been tested in this way, with a sequence of confirmatory tests, and you have been told that you are HIV positive, you can be confident of the result. The rest of the information on this page does not apply to you.
“An HIV diagnosis is never made on the basis of a single test result.”
On the other hand, you might have been tested with a rapid, point-of-care test at a location where the staff could not do the confirmatory tests immediately. If your initial result was reactive, the staff may have asked you to come back on another day or to go to another healthcare facility for the follow-up testing. Or you might have taken the test yourself, using a device for self-testing or home testing.
If that is the case, the confirmatory testing is essential. There is a possibility that your reactive result is in fact a false positive. The only way to know is to go and have it checked by a qualified healthcare professional.
antibody
A protein substance produced by the immune system in response to a foreign organism. Many diagnostic tests for HIV detect the presence of antibodies to HIV in blood.
To put this in individual terms:
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What Causes False Positive Results
HIV tests are based on the detection of antibodies to HIV. These are proteins produced by the immune system in response to a foreign substance, such as HIV. The main cause of false positive results is that the test has detected antibodies, but they are not antibodies to HIV they are antibodies to another substance or infection. Tests are not meant to react to other types of antibodies, but it sometimes happens.
There are other reasons why a test may give a false positive result. Depending on the testing device, reading the test result may rely on subjective interpretation. When the result is borderline, experienced staff give more consistently accurate results. A false positive result could also be the result of a sample being mislabelled, mixed up with another persons, or some other clerical or technical error.
Less commonly, false positive results may occur in people who have recently had a flu vaccine, are taking part in an HIV vaccine study, or have an autoimmune disease .
Is A Blood Test For Genital Herpes Included When I Ask To Be Tested For Everything Why Does Cdc Recommend Testing For Other Stds But Not Herpes
Herpes blood tests may or may not be included. Your doctor chooses STD tests based on your sexual behaviors , as well as how common the infection is in the area that you live in. This is why you should have an open and honest discussion with your doctor about your sex practices and history. When you go in for STD testing, it is important to ask your doctor which infections you are and are not being tested for, and why.
STD tests are usually done for infections that have serious outcomes if they are not treated. For example, finding and treating curable STDs like chlamydia can stop them from causing serious complications like infertility in women. Genital herpes does not usually result in serious outcomes in healthy, non-pregnant adults. More often, the stigma and shame from a genital herpes infection can be more troubling to someone who is infected than the disease itself. If you are worried about genital herpes, you should talk with your doctor about whether you should be tested.
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What Is A False Negative Test Result
A false negative result suggests that you do not have a particular disease or condition when in fact, you do. Numerous medical tests can produce false negative results, ranging from pregnancy, tuberculosis and Lyme disease to tests for alcohol and drugs in the body.
For STIs like gonorrhoea and chlamydia, getting a false negative result would indicate that the person doing the test hasnt got an infection when actually they do. This can be problematic for numerous reasons. It may mean that someone experiences delays with their treatment, due to not knowing theyre infected. It could also make it more likely that someone would inadvertently infect someone else .
Where Can I Get More Information
Health care providers with STD consultation requests can contact the STD Clinical Consultation Network . This service is provided by the National Network of STD Clinical Prevention Training Centers and operates five days a week. STDCCN is convenient, simple, and free to health care providers and clinicians. More information is available at www.stdccn.orgexternal icon.
Division of STD Prevention Centers for Disease Control and Prevention
Research Triangle Park, NC 27709-38271-800-783-987
References
1. OFarrell N, Morison L, Moodley P, et al. Genital ulcers and concomitant complaints in men attending a sexually transmitted infections clinic: implications for sexually transmitted infections management. Sexually transmitted diseases 2008 35:545-9.
2. White JA. Manifestations and management of lymphogranuloma venereum. Current opinion in infectious diseases 2009 22:57-66.
3. Kreisel KM, Spicknall IH, Gargano JW, Lewis FM, Lewis RM, Markowitz LE, Roberts H, Satcher Johnson A, Song R, St. Cyr SB, Weston EJ, Torrone EA, Weinstock HS. Sexually transmitted infections among US women and men: Prevalence and incidence estimates, 2018. Sex Transm Dis 2021 in press.
4. CDC. Sexually Transmitted Disease Surveillance, 2019. Atlanta, GA: Department of Health and Human Services April 2021.
5. Torrone E, Papp J, Weinstock H. Prevalence of Chlamydia trachomatis Genital Infection Among Persons Aged 1439 Years United States, 20072012. MMWR 2014 63:834-8.
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Finding The Cause Of A False
Since there are various reasons for false-positive results, individuals should speak with a doctor about the probable cause. Some may be due to human error, such as a technical or clerical oversight.
However, a false-positive result can also result from another condition, such as an STI or an autoimmune disorder. Autoimmune disorders that may cause false-positive results include lupus and rheumatoid arthritis.
Chlamydia Cdc Fact Sheet
Chlamydia is a common sexually transmitted disease that can be easily cured. If left untreated, chlamydia can make it difficult for a woman to get pregnant.
Basic Fact Sheet | Detailed Version
Basic fact sheets are presented in plain language for individuals with general questions about sexually transmitted diseases. The content here can be syndicated .
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Are People With Genital Herpes At Increased Risk Of Getting Infected With Hiv
Yes, studies show that HSV-2 infection increases the risk of getting HIV infection, even when there are no symptoms of genital herpes. HSV-2 infection can cause tiny breaks in the genital and anal area that allow HIV to enter into the body. Herpes infection also attracts the type of cells that HIV infects to the genital area. This increases the chance of getting HIV, if exposed.
Is Alzheimers Disease Related To Hsv
Alzheimers disease is a progressive brain disease that develops as a result of a complex series of events occurring in the brain over a long period of time. The causes of Alzheimers disease may include genetic, environmental, and other factors. Several different factors have been statistically linked to Alzheimers disease, including HSV-1 infection. However, some investigations suggest that viruses other than HSV-1 may influence Alzheimers disease. More research is needed to determine whether or not there is a causal link between HSV-1 infection and Alzheimers disease.
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How Do People Get Chlamydia
Chlamydia is transmitted through sexual contact with the penis, vagina, mouth, or anus of an infected partner. Ejaculation does not have to occur for chlamydia to be transmitted or acquired. Chlamydia can also be spread perinatally from an untreated mother to her baby during childbirth, resulting in ophthalmia neonatorum or pneumonia in some exposed infants. In published prospective studies, chlamydial conjunctivitis has been identified in 18-44% and chlamydial pneumonia in 3-16% of infants born to women with untreated chlamydial cervical infection at the time of delivery.9-12 While rectal or genital chlamydial infection has been shown to persist one year or longer in infants infected at birth,13 the possibility of sexual abuse should be considered in prepubertal children beyond the neonatal period with vaginal, urethral, or rectal chlamydial infection.
People who have had chlamydia and have been treated may get infected again if they have sexual contact with a person infected with chlamydia.14
Genital Herpes Is Common Why Doesnt Cdc Recommend Testing Everyone For This Std
CDC does not recommend herpes testing for people without symptoms. This is because diagnosing genital herpes in someone without symptoms has not shown any change in their sexual behavior nor has it stopped the virus from spreading. Also, false positive test results are possible. Even if you do not have symptoms, you should talk openly and honestly about your sexual history with your doctor to find out if you should be tested for any STDs, including herpes.
Although CDC does not recommend that everyone get tested for herpes, herpes testing may be useful in some situations. Herpes blood tests might be useful
- If you have genital symptoms that could be related to herpes,
- If you have a sex partner with genital herpes, or
- If you want a complete STD exam, especially if you have multiple sex partners.
Please note that while a herpes blood test can help determine if you have herpes infection, it will not be able to tell you who gave you the infection.
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When Should I Get Tested
Don’t delay getting tested if you think you might have chlamydia. Being diagnosed and treated as soon as possible will reduce your risk of developing any serious complications of chlamydia.
You can get a chlamydia test at any time although you might be advised to repeat the test later on if you have it less than 2 weeks since you had sex because the infection might not always be found in the early stages.
You should consider getting tested for chlamydia if:
- you think you could have a sexually transmitted infection
- a sexual partner tells you they have an STI
- you’re pregnant or planning a pregnancy
- you’re offered a chlamydia test as part of the NCSP
If you live in England, you’re a woman under 25 and sexually active, it’s recommended that you have a chlamydia test once a year, and when you have sex with new or casual partners.
If you live in England, you’re a man under 25 and sexually active, it’s recommended that you have a chlamydia test once a year if you are not using condoms with new or casual partners.
If you have chlamydia, you may be offered another test 3 to 6 months after being treated. This is because young adults who test positive for chlamydia are at increased risk of catching it again.
Description Of The Study Cohort
Figure depicts the process by which index events were selected for inclusion in outcome analyses. During the two-and-a-half-year period, a total of 94,426 tests were performed in primary care and sexual health clinics with 6817 testing positive overall . There were clear differences in rates of positivity by gender, age and ethnicity for the cohort tested. Males made up only 19.3% of those tested, but were more likely than females to test positive for chlamydia and gonorrhoea . The majority of those testing positive were aged under 25 years . In this age group , 16.1% of males and 9.5% of females were diagnosed with chlamydia, and 5.7% of males and 0.6% of females diagnosed with gonorrhoea. Individuals of Pacific ethnicities had the highest proportion of positive results , followed by Maori , European and Asian . Following application of test-retest criteria , 6530 positive index events were included in the dataset for further analysis .
Fig. 1
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How Can I Reduce My Risk Of Getting Chlamydia
The only way to avoid STDs is to not have vaginal, anal, or oral sex.
If you are sexually active, you can do the following things to lower your chances of getting chlamydia:
- Be in a long-term mutually monogamous relationship with a partner who has been tested and has negative STD test results
- Use latex condoms the right way every time you have sex.
What To Think About
- If a chlamydia infection is suspected, do not have sexual intercourse until the test results have come back. If you have a chlamydia infection, do not have sexual intercourse for 7 days after the start of treatment. Your sex partner should also be treated for a chlamydia infection so that you don’t get reinfected and so that others don’t get infected.
- Only one laboratory test is needed to diagnose chlamydia. Your doctor can choose which test to use.
- Screening for and treating chlamydia can help prevent pelvic inflammatory disease . To learn more about the treatment of a chlamydia infection, see the topic Chlamydia.
- Other sexually transmitted infections may be present at the same time as chlamydia. So it is important to be tested and treated for all STIs. Chlamydia as well as other STIs can also increase the chance of getting human immunodeficiency virus . An HIV test may be offered at the same time as a test for chlamydia or other STIs.
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Testing Before The Recommended Incubation Period
One reason that false negatives occur is due to testing prior to the recommended window period for testing. No STD test is accurate immediately after sex as it takes time for the bacteria or virus to reach a detectable state or for the body to present an immune response.
The length of time that you are required to wait depends on the particular test that you take and can be anywhere from 7 28 days after exposure. You will see this on the STD tests on Your Sexual Health, displayed as the Accuracy From period.
Each test carries an Accuracy From date which is the time period when the results reach the required level of accuracy. You should always test after this date to avoid false negative results.
I Was Treated For Chlamydia When Can I Have Sex Again
You should not have sex again until you and your sex partner have completed treatment. If your doctor prescribes a single dose of medication, you should wait seven days after taking the medicine before having sex. If your doctor prescribes a medicine for you to take for seven days, you should wait until you have taken all of the doses before having sex.
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What Is A False Positive
A false positive is when a test result comes back positive, but the patient does not have an STD. This outcome is much rarer than a false negative, because it is a lot harder to detect something that is not there. It would usually be caused by an issue with the test itself.
If you take a test that offers a positive result, but you are highly uncertain of the accuracy, you should take a retest. There are a number of different kinds of STD tests that work in slightly different ways, whether its a different sample type or a different manufacturer. Retesting with a different type of test should offer you increased confidence in the results.
Dr Bani
Is There Anything Else I Need To Know About A Chlamydia Test
Chlamydia testing enables diagnosis and treatment of the infection before it can cause serious health problems. If you are at risk for chlamydia due to your age and/or lifestyle, talk to your health care provider about getting tested.
You can also take steps to prevent getting infected with chlamydia The best way to prevent chlamydia or any sexually transmitted disease is to not have vaginal, anal or oral sex. If you are sexually active, you can reduce your risk of infection by:
- Being in a long-term relationship with one partner who has tested negative for STDs
- Using condoms correctly every time you have sex
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