Medical clinics and doctor’s offices can test for some STDs but most don’t routinely do these tests. The reason why has to do with the tests themselves and the requirements from the insurance companies that approve payment for the tests. Here are some of the most common questions about testing for STDs.
How are STDs Diagnosed?
A sexually transmitted infection (STI) or disease (STD) is diagnosed according to the history of symptoms provided by the patient, by the findings on a physical exam and by the lab test that confirms the infection. In order to make diagnosis and treatment as easy as possible and available to as many people as possible, some rapid-response type tests have been developed that can be used at community screenings and other events without a history or physical exam. These rapid response tests are usually screening tests, not the ones used for an accurate diagnosis. For medical people, a positive screening test means ‘take a closer look.’
Does the Type of Doctor’s Office Matter?
Although almost any doctor’s office or healthcare center can test for STDs, you must ask for it. Often routine blood work along with your annual exam does not include STD testing. Even if certain STDs are included in your annual exam, it will not be the entire panel and the particular STD you are worried may not be included.
As uncomfortable as it may be, you must discuss with your doctor your concerns and which STDs you want to be tested for. Your health care provider will be able to further advise you on the necessity of the test concerning the disease you are worried about and can advise you on whether or not follow-up tests are needed to avoid false negatives.
Your doctor can also make sure you’ve waited long enough after sex to get tested, as different STDs have varying waiting periods before a test will detect the presence of the infection. According to One Medical, you must wait two weeks before a test can detect gonorrhea or chlamydia. The waiting period for syphilis is one week to three months and six weeks to three months for HIV and hepatitis.
What are the types of tests available?
It would be great if, with one tube of blood or mouth swab, we could find out about our cholesterol and chlamydia. Some older tests are still being used, and some new but expensive tests are on the market.
Bacterial culture: In this test, some of the fluid from the cervix or penis is placed on a culture medium to see if anything grows. After 24 and 48 hours, lab techs look at samples of the bacterial growth on the culture plate. This test has an important role in detecting new strains of bacteria that are becoming resistant to commonly used antibiotics, such as what is happening with gonorrhea. Many times, a culture will be taken if an initial treatment seems to be failing.
Sensitivity testing: This test may be included as part of bacterial culture test to identify which antibiotic will be most effective to cure the infection. This culturing and sensitivity testing is called “culture and sensitivity” or shortened to C & S in common medical slang.
Antibody tests: Our immune systems respond to invaders by making little weaponized proteins to fight off the infection. These proteins called antibodies will show up in body fluids such as blood and even more easily accessible body fluids such as urine. The downside is the risk of testing for an infection before the antibody level is high enough to show up which will give a false negative result.
Antigen tests: Some proteins that are part of the cell wall membrane of various viruses and bacteria can be tested directly. These are usually blood tests.
Enzyme-linked immunosorbent assay (ELISA): This test detects both bacterial antigen and the antibody. A positive result to this test will show exposure to the bacteria at some time. It doesn’t identify if the current infection is caused by the bacteria. An ELISA may be used to confirm syphilis (the Treponema pallidum bacteria).
RNA tests: These expensive tests look for the genetic material, or RNA, of the germ itself.
Gram Stain: An old fashioned but effective test called a Gram stain can be done wet or dry. The swab is rubbed across dry skin or wet tissues including mucous membranes. The swab is then rubbed on a slide and a series of dyes (stains) will be applied. The provider looks at the results under the microscope. Gram positive bacteria will show as blue-purple color and gram negative bacteria will appear red. A Gram stain also identifies the bacteria by shape. Gram + cocci are round in shape. Gram – rods are rod-shaped. A gram stain is often accompanied by a sensitivity test (see above).
Viral cultures: These tests can sample a sore that has fluid, such as a herpes lesion, and determine if any of the virus is present by growing it like the bacterial culture. Viral cultures are challenging and can have a high rate of false negatives.
Many of these specialized tests are not available in the typical doctor’s office, but require a trip to a laboratory.
What is the difference between screening tests and diagnostics?
When lab tests are evaluated, they have to pass levels of accuracy. They have to both find the specific germ/virus being looked for and they have to find it every time. Also, they can’t call a positive if there is no infection. Each test is specific for the protein antibody, virus or germ being looked for. There isn’t one test that can check for everything.
The less expensive and easy to use tests, such as the ones that use cheek swabs and are done in twenty minutes, are considered screening tests. A screening test cannot always determine an old infection from a new one, and they usually cannot be trusted to find an infection early. Screening tests have a higher rate of false negatives and false positives. A false negative is a result that shows as negative when the infection is actually there. A false positive is a positive result given by the test when no infection is present. Screening tests are usually used to decide which people need to take the most expensive, more accurate diagnostic tests.
A diagnostic test is used to determine a specific infection, such as with the bacterial or viral culture, and to make sure the screening test didn’t give a false negative or positive. Diagnostic tests can also point to specific treatments.
Why not check for everything?
These bugs (virus and bacteria) tend to travel together but the treatments are not the same. The test for gonorrhea will not tell us anything about chlamydia, though we know these two are commonly seen together. Treatment for one will not treat both. HIV virus and syphilis bacteria travel together, but the diagnostic tests and treatments are different for each.
In the presence of a single positive screening test for any STD, however, many medical providers will recommend checking for everything by using the more expensive, diagnostic tests. This recommendation is made even in the absence of symptoms because some of the trickier germs/viruses will hide and not give enough symptoms to worry about. The exception to this rule is herpes. These lesions will usually only be cultured during an outbreak, though the virus can spread at any time.
Why not just always use the more expensive, diagnostic tests?
That’s probably overkill and the tests get very pricey. This matters because insurance companies decide if they are going to reimburse for the cost of the test. They usually set standard guidelines for approving the test, such as symptoms, physical exam suggestive of infection or a positive screening test. They won’t pay for the diagnostic tests to be used in the absence of symptoms or physical exam results, such as a typical sore. That means the patient, you, end up having to foot the bill. Screening tests are less invasive, less expensive and work well most of the time.
Medical providers do not actually have to get laboratory tests to confirm a diagnosis. A history with symptoms and a physical exam consistent with the disease is standard practice to treat. Many only use lab tests to either confirm the diagnosis or to evaluate if the initial treatment doesn’t seem to be working.
When are STDs part of a normal medical workup?
There are two times when the standard of medical practice is to check for everything. This is during prenatal care and care for those infected with HIV or TB. Medical clinics that specialize in diagnosing and treating STDs will also usually do a comprehensive workup because those who are looking for answers need detailed and specific answers. Specialty clinics are also usually at the forefront of new and emerging STDs, and this field of medicine is changing rapidly with bacteria which are mutating and developing antibiotic resistance.