Chlamydia trachomatis nucleic acid hybridization test
What is this test?
This test checks for gene sequences in bacterial DNA. It is used to help diagnose infections caused by the Chlamydia trachomatis bacteria.
Why do I need this test?
Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:
When and how often should I have this test?
When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.
Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.
The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.
How should I get ready for the test?
Written consent may be required for a Pap smear or colposcopy with cervical biopsy. Review the consent form with the healthcare worker and ask any questions that you have before signing the consent form.
Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. If possible, schedule the procedure one week after your menstrual period, because this is when the cervix is the least prone to bleeding. Do not douche or have sexual intercourse for 24 hours before the procedure.
You may be asked to urinate prior to your Pap smear or biopsy procedure. This will make it easier for the healthcare worker to see your cervix during the procedure, and may make the procedure more comfortable for you.
Before collection of urethral cells and/or urethral discharge for this test, you should not urinate during the hour prior to the test. This is because urine may minimize or clear your urethra (the tube that drains urine) of any organisms (germs), thus affecting the results of this test.
Urinate an hour or more before a sample is collected..
How is the test done?
An endocervical or urethral sample may be collected for this test.
For both a Pap smear and colposcopy with cervical biopsy, you will be asked to lie on your back with your legs spread and feet placed in stirrups. A speculum will be inserted into your vagina. This tool is used to gently spread apart your vagina. For a Pap smear, a small brush is used to collect surface cells off the cervix. The sample off the brush is then sent for testing.
If a colposcopy is done, a special magnifying instrument called a colposcope is used to inspect your cervix. After the cervix is cleaned, a small piece of tissue will be removed. Tissue samples may be collected from different areas of the cervix. After the biopsy, a solution may be applied to help stop bleeding. Less commonly, stitches or a special heating tool may be used to stop bleeding. A tampon may be placed to help prevent further bleeding.
A urethral culture procedure is used to collect cells samples and/or urethral discharge. This test is usually done on males only. For this procedure, you will be asked to lie on your back. The tip of the penis will be cleaned. A special thin swab will be inserted into the urethra. The swab will gently be twisted side to side and then remain still for a few seconds before it is removed. This is to allow the swab to absorb enough fluid to be cultured. It may be possible to get a sample by “milking” the urethra for discharge. Ask the healthcare worker if this is an appropriate option.
How will the test feel?
The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.
You may feel mild discomfort, cramping or pain during a Pap smear. During and after a colposcopy, you may feel discomfort, cramping, or pain. Generally, a colposcopy may be more uncomfortable than a pap smear.
A urethral culture generally takes less than a minute. However, you may feel discomfort when the swab moves in the urethra.
What should I do after the test?
After a Pap smear, you may experience some light spotting (mild, occasional bleeding from the vagina). Generally, there are no activity restrictions after a Pap smear.
After a colposcopy, avoid heavy exercise for 24 hours. Some light bleeding or spotting is normal, but report heavy bleeding to your healthcare worker. It is normal after this procedure to have a gray-green, foul-smelling vaginal discharge for a few days. Contact your healthcare worker if this continues beyond three weeks.
After a colposcopy, avoid vaginal sex, douching, and tampon use for at least one week. Follow the instructions given by your healthcare worker. If a tampon was placed during the procedure, your healthcare worker will tell you when it may be removed, which is usually after 8 to 24 hours.
After a sample has been collected, avoid all sexual activities until you receive your results and speak to your healthcare worker.
What are the risks?
Cervical cells/tissue: A cervical cell sample is collected by a Pap smear. If a larger tissue sample is needed, a colposcopy with cervical biopsy may be performed. Both procedures may cause light bleeding from the vagina. The risk of bleeding is greater with a biopsy because more tissue is removed. If you have a medical condition, or are using a medication or supplement that causes excessive bleeding, you are at a higher risk of bleeding during or after this procedure. The person doing this procedure may need to perform it more than once. Talk to your healthcare worker if you have any concerns about the risks of a Pap smear, colposcopy, or cervical biopsy.
Ask the healthcare worker to explain the risks of this test or procedure to you before it is performed.
What are normal results for this test?
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following is considered to be a normal result for this test:
What follow up should I do after this test?
Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.
If you have a positive urethral culture, you may need to have the test repeated to monitor the treatment of your diagnosed condition. Additionally, all of your sexual partners may need to be treated. Follow the instructions given to you by your healthcare worker regarding sexual activities.
Where can I get more information?
 Johnson RE, Newhall WJ, Papp JR, et al: Screening tests to detect Chlamydia trachomatis and Neisseria gonorrhoeae infections--2002. MMWR Recomm Rep 2002; 51(RR-15):1-38.
 Koumans EH, Johnson RE, Knapp JS, et al: Laboratory testing for Neisseria gonorrhoeae by recently introduced nonculture tests: a performance review with clinical and public health considerations.. Clin Infect Dis 1998; 27:1171-1180.
Last Updated: 4/4/2014
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