Sexually transmitted infections (STIs) and STDs are continually on the increase as there are more and more reported cases of new infections worldwide. With more and more people being diagnosed, it becomes pertinent to ask: How accurate are the diagnostic tests that spot these diseases?
Here are all you need to know about the diagnostic testing methods of various STDs.
Chlamydia and Gonorrhea
If you go into a hospital or medical laboratory to get tested for chlamydia or gonorrhea (another common bacterial STI), it’ll likely be done via a urine sample or a swab from the rectum or throat.
The test itself is called a nucleic acid amplification test (NAAT). It looks for the unique DNA or RNA of the bacteria or virus, and it amplifies it exponentially. That makes it easy for doctors to spot.
Cultures which is a past technique of testing (but still commonly used) took longer and required that more of the virus be present in order to pick it up. Nucleic acid amplification tests (NAAT) are very good, and they have moved diagnostics forward. These are incredibly accurate compared to most old diagnostic techniques.
Using this testing method, a false positive is incredibly rare (99 percent of the time tests that come back negative are accurate). And if you do have the STI, it’ll pick it up more than 90 percent of the time. As a matter of fact, research confirms these new tests are much better than the old ones as they typically pick up 20 to 50 percent more chlamydia infections than cultures and other earlier tests did.
Trichomoniasis is a parasite that typically infects people without causing any symptoms. The best test to pick it up is, again, a NAAT. Research has shown that the test can be 76 to 100 percent accurate, though the parasite can also be picked up in a culture. Trichomoniasis is difficult to find in a urine sample because urine can be toxic to the parasite.
It is best not to test for herpes in people that show no symptoms. Tests however can be done on people who have symptoms that could be related to herpes, have had sex with a partner who has herpes, or people who have multiple partners.
If you have a sore (or what you suspect to be a sore), the best test is what’s called a polymerase chain reaction (PCR) test. Recent studies have shown that these tests pick up the virus more than 96 percent of the time.
The test requires your medical laboratory scientist to take a sample from the sore, and a lab test would look for genes from the herpes virus. This test is very effective.
Also, a culture can be done to check for the herpes virus. Other highly-accurate blood tests that look for antibodies that fight the herpes virus also exist. If you don’t have a sore but think you may have been exposed to the virus from someone who has it, the blood test could be a good option.
The bacterium that causes syphilis, spirochetes Treponema pallidum, cannot be cultured and this has restricted physicians to imperfect blood tests that try to identify antibodies in the blood. One study published in JAMA found the tests to be at least 85 percent accurate.
Most HPV that causes cancer; strains 16 and 18, for the most part don’t cause symptoms. That means if you notice warts, they’re likely from HPV strains 6 or 11 which—with the exception of rare cases—are not linked to cancer.
There is currently no approved HPV test for men, nor an FDA-approved test to find the virus anywhere besides the cervix. That could be because 85 to 90 percent of people who are sexually active have had HPV and most people tend to fight off the infection on their own.
The main tests for HIV are blood tests. “The tests out there detect HIV earlier than other tests. Research finds blood tests pick up the disease 99.5 percent of the time.
There are three types of tests available; nucleic acid tests which look for the virus in the blood, antigen/antibody tests which look for both HIV antibodies produced by your immune system and antigens that are produced even before antibodies develop, and antibody tests which look for antibodies in your blood or saliva.
Generally, blood tests from a vein detect HIV sooner than those from pricks or fluid swabs.