What STIs are "testable" — and who is infected, anyway?

Originally Published: September 21, 2007 - Last Updated / Reviewed On: July 2, 2012
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Dear Alice,

I recently became sexually active at 21, and my partner is a bit older and has had multiple partners. At this point, we are exclusive, and have used a condom on the few occasions we have had intercourse. I went to the local Planned Parenthood recently, and am now on a birth control pill (I am absolutely sure I don't want or need to be pregnant at this point or ever in my life, personal choice...). I realize that although the pills are great for preventing conception, they are not effective at preventing STI's, where as the condom has at least pretty good effectiveness for many of them.

I asked my partner to be tested for STI's before I went to PP, and had assumed that if he was tested and came back with negative results (as in no infections) it would be fairly safe to have intercourse with out the condom on the STI issue, if neither of us were active outside of the relationship. While visiting the clinic, I learned that apparently, many of the STIs are not tested for, and some of them in theory can't be tested for. I have tried to sort out which ones can and can't be tested for and get further info on the web about this, but I have failed to find it. I got close with an archive article here, but I am still trying to find out the "truth"... I would love to see something like a chart of what STI's are "testable", routinely tested for, and possibly the infection rate in the general public so I could make a more informed decision on the further use of the condom.

Thanks,

Trying to make a more informed decision

Dear Trying to make a more informed decision,

You’re doing an excellent job of looking out for your health and being a responsible sexual partner. Many people have run up against the frustration of fuzzy answers regarding sexually transmitted infections (STIs), testing and safer sex. Unfortunately, there are few “truths,” significant complexity, and lots of gray area. It sounds like you are off to a great start: talking with your partner about sexual histories, birth control, and STI testing. Limiting your number of lifetime partners, using condoms and other barrier methods, and getting tested for STIs with new sexual partners will also help you reduce your risk. But, in the end, sex involves some risk, so you and your partner have to figure out what you’re comfortable with.

Testing for STIs involves weighing risks, probabilities, and costs, because testing everyone for everything would be very expensive and is much more likely to result in “false positives” (where you test positive, but you don’t have the infection) and “false negatives,” where you test negative but do have the infection. For viral infections like herpes and HPV that come and go on their own, it’s difficult to test when symptoms aren’t present because the most accurate tests use samples from the lesions the virus causes. And for bacterial infections like chlamydia and gonorrhea, the tests are not always as accurate as one would like, generating many false negatives, so many clinics routinely treat for them if there has been exposure, and don’t even bother with the tests. Thus, it makes more sense for medical providers to make diagnoses based on a combination of information including your sexual history, symptoms, and testing (where indicated).

You asked about the number of infections among the general public. It’s difficult to measure prevalence (how many people have the infection), because many times infections are asymptomatic so people don’t get tested. Also, different infections have different reporting requirements. For example, information is gathered much more systematically for chlamydia and gonorrhea than for herpes. Because information is reported in different ways, it can be difficult to compare one statistic to another. Also, prevalence differs significantly among subpopulations (based on age, ethnicity, gender, sexual orientation, geography, etc.) For example, even though in any given year only .3% of people in the U.S. might have a chlamydia infection, it’s one of the most common STIs among young people. In 2005, the CDC reported that of women screened in selected family planning clinics, the proportion of positive tests was 6.3% among 15-24 year olds. To think about it another way, according to one study, Trichomoniasis, HPV, and Chlamydia accounted for 9 out of 10 new STI infections among 15-24 year olds in 2000.

Thus, knowing the prevalence in the general population may not be your best guide, either for judging what to test for or what to watch out for. This may explain why it’s hard to find clear guidelines about testing or overall population statistics — good medical providers make informed judgments based on each person’s situation, and data about different subpopulations. In any case, here are some general prevalence numbers for common STIs and information about testing. The following data are from 2010, from the Centers for Disease Control and Prevention.

Trichomoniasis — This is the most common curable infection in the U.S., with about 3.7 million people infected. Out of that 3.7 million, only about 30% will actually develop symptoms. The infection is more common in women than in men and more common in older people than younger people. Diagnosis is made through visual examination and laboratory test.

Bacterial Vaginosis (BV) — This is the most common bacterial infection among women of childbearing age. Overall prevalence is unknown, but as many as 16% of pregnant women have BV. BV is diagnosed by a lab test with a sample of vaginal fluid.

Human Papillomavirus (HPV) — Some strains of HPV cause genital warts and some strains are associated with cervical cancer. Cervical cancer affects about 12,000 women in the U.S. every year. Genital HPV is thought to be the most common STI in the U.S. — 50-75% of sexually active people will acquire it at some point in their lives. Although there is no cure, it appears the body often clears the virus on its own. Medical providers mainly diagnose HPV based on the presence of warts or, for women, an “abnormal” Pap test. If a Pap test has an abnormal or unclear reading, it will be followed up with a colposcopy and/or an HPV test. Pap tests look for cell changes caused by HPV infection, the HPV tests looks for the virus itself. There is currently no test for HPV in asymptomatic men. For the most recent recommendations for HPV screening, you can check out Cervical cancer info on the net. An HPV vaccine was introduced in 2006 that protects men and women against the strains of HPV than cause genital warts and cancer.

Herpes — One out of six adults and adolescents has had Herpes Simplex Virus 2 (genital herpes). Like HPV, herpes is difficult to diagnose without visible sores, and many people have no symptoms. The infection is slightly more common in women than men. In heterosexual penetrative intercourse, a man is more likely to pass it on to his female partner than a woman is to give it to her male partner. Although there is no cure, a person with active herpes can use daily medication to reduce the likelihood of transmission to a sexual partner. A blood test is available but it isn’t always conclusive, so it is not usually done unless someone has symptoms or suspects an exposure.

Chlamydia — In 2009, 1.2 million cases of chlamydia were reported to the CDC, but it is estimated that 3 million cases occur annually in the U.S. Chlamydia infections are under-reported because people are so frequently asymptomatic. Approximately 75% of infected women and 50% of infected men have no symptoms. Testing can be done with a swab test in the penis, vagina, cervix, anus and/or throat. Some clinicians use a urine test rather than a penis or cervical swab.

HIV — A 2006 study from the Centers for Disease Control estimates an overall prevalence of HIV in the United States at about .2% - that is, 2 out of every 1000 people, or around 900,000 people all together. Again, prevalence numbers are significantly different depending on factors such as your ethnicity, where you live, and age. HIV testing can be done with a blood test or a mouth swab. It may take up to 3 months after exposure to HIV (this is often called the “window period”) for your body to develop the antibodies that are measured by the test. Therefore, even if you have HIV, you might not test positive right away.

Hepatitis B — There are between 800,000 and 1.4 million people in the U.S. with chronic Hepatitis B. Hepatitis B is incurable, but there is a vaccine to prevent it. It is diagnosed with a blood test, but health care providers will not automatically test you for it if you have received the vaccine.

Gonorrhea — Each year, approximately 650,000 or .2% of the population is infected with gonorrhea. In 1999, 77% of all reported gonorrhea cases occurred among African Americans, and 75% of all reported gonorrhea cases were found in people ages 15-29. Testing for gonorrhea and chlamydia are most often done simultaneously, with either a urine test or a swab test in the penis, vagina, anus or throat.

Syphilis — Over 36,000 cases of syphilis were reported in the U.S. in 2006, including 9,756 cases of primary and secondary (P&S) syphilis. Most P&S syphilis cases occur in people ranging from 20 to 39 years of age. Between 2005 and 2006, the number of reported syphilis cases increased 11.8 percent. Some health care providers can diagnose syphilis by examining material from sores using a special microscope called a dark-field microscope. If syphilis bacteria are present in the sore, they will show up when observed through the microscope. Another way to test for syphilis is through a blood test.

Pelvic Inflammatory Disease (PID) — Approximately 750,000 to 800,000 women in the U.S. experience an episode of acute PID. A large proportion of the ectopic pregnancies occurring every year are due to the consequences of PID and up to 10 — 15% of these women may become infertile as a result of infection. STIs are only one cause of PID. It can also be caused by regular vagina flora. Diagnosis of PID can be very difficult. There is no testing for Pelvic Inflammatory decease. Instead, diagnosis is based off of clinical findings and sometimes laparoscopy.

Lymphogranuloma Venereum (LGV) — LGV is a type of rectal infection that is often mistakenly thought to be caused by ulcerative colitis. The frequency of LGV infection is thought to be rare in industrialized countries, but it’s identification is not always obvious. As a result, so the number of cases of LGV in the United States is unknown. Outbreaks in the Netherlands and other European countries among men who have sex with men have raised concerns about cases of LGV in the U.S. LGV is diagnosed by a health care practitioner evaluating symptoms and lesions.

Numbers, numbers, numbers, and all you probably want is a straightforward answer: “Should I use this condom, or not???” If only the answer were so simple. As you probably realize, the only way to be 100% certain you don’t get any infections is to not have any oral, vaginal, or anal sex. Clearly, most people eventually decide to take the plunge and explore the joys of sex. At that point, communication and cooperation between you, your partner(s), and your medical provider becomes crucial for keeping things as safe as possible. If you would like to get tested for any or all of the above testable STIs, you should see your health care provider. Columbia students can make an appointment with Medical Services through Open Communicator or by calling x4-2284. Free and confidential HIV tests are also available to Columbia students through GHAP.

It’s also important to realize that certain STIs aren’t the end of the world, and as the prevalence numbers show, most people don’t have them. However, it’s good to always be careful and also relax and enjoy your sexuality — hopefully the two can go hand in hand!

Alice