Three laboratory techniques used when diagnosing gonorrhea include: a Gram stain, gene detection, and a lab culture. The staining sample test tends to work better when diagnosing the condition in men than in women, and the gene test is more accurate than culturing the bacteria. Only 1 in 2 women will have a positive Gram stain when this method of diagnosing gonorrhea is used.
Healthcare providers usually use three laboratory techniques when diagnosing gonorrhea, which include:
- Staining samples directly for the bacterium
- Detecting bacterial genes or DNA in urine
- Growing the bacteria in laboratory cultures.
Many healthcare providers prefer to use more than one test in order to increase the chance of an accurate diagnosis.
The staining test involves placing a smear of the discharge from the penis or cervix on a slide and staining the smear with a dye. Then the healthcare provider will use a microscope to look for bacteria on the slide. Results from this test are usually available right away. Although this test is quite accurate for men, it is not usually accurate in women. Only 1 in 2 women with gonorrhea will have a positive Gram stain.
In most cases, healthcare providers will use urine or cervical swabs for a new test that detects the genes of the bacteria. These tests are more accurate than culturing the bacteria.
The laboratory culture test involves placing a sample of the discharge onto a culture plate and incubating it for up to 2 days to allow the bacteria to grow. The sensitivity of this test will depend on the site from which the sample is taken. Cultures can be used to:
- Detect gonorrhea in the cervix with a 90 percent chance of accuracy
- Detect gonorrhea in the throat
- Test for drug-resistant forms of the bacteria.