Advantages and Accuracy of Rapid STD Tests

Rapid STD tests have been designed to save people time, effort, and stress when diagnosing a sexually transmitted infection. Some are performed in the doctor's office or clinic, while others can be done in the comfort and privacy of your home.

The aim of these tests is to avoid one of the most common problems seen at STD clinics: people who fail to return for their results. Oftentimes, a person will get up the nerve to be tested only to back out when its time to receive the news. As a result, an infection can be left untreated and allowed to spread to others.

A rapid STD test allows you to get your results in minutes rather than days. If the test is positive (meaning that you've been infected), you have the opportunity to get immediate treatment rather than having to come back to fill a prescription. With diseases like HIV, this is important since early treatment translates to a lower risk of illness and a longer lifespan.

The newer tests also aim to overcome another factor that keeps many people away: needles and blood. Depending on the disease, a rapid test may only require a swab of body fluid or a urine sample (in addition to the traditional blood or finger prick tests).

Not all rapid tests are created equal. Some have higher sensitivity and specificity than others. Sensitivity is the ability of a test to correctly identify those with the disease (a true positive rate), while specificity is the ability to correctly identify those without the disease (a true negative rate).

When testing during acute infection, rapid STD tests offer the average sensitivity and specificity:

• Gonorrhea: 86 percent sensitivity and 97 percent specificity
• Syphilis: 85 percent sensitivity and 91 percent specificity
• Chlamydia: 86 percent sensitivity and 97 percent specificity
• Hepatitis B: 97 percent sensitivity and 99 percent specificity
• Human papillomavirus: 86 percent sensitivity and 84 percent specificity
• Herpes simplex: 93 percent sensitivity and 99.9 percent specificity
• HIV (in-office, finger prick): 99 percent sensitivity and 99.9 percent specificity
• HIV (at-home, oral swab): 92 percent sensitivity and 99 percent specificity

Unfortunately, a lower sensitivity rate translates to an increased risk of a false negative result (meaning that a person is given the "all-clear" when he or she is actually infected). With the currently available at-home HIV test, a 92 percent sensitivity translates to one false negative out of every 15 tests.

This is why certain bacterial diseases (like syphilis, gonorrhea, and chlamydia) are more accurately diagnosed with a culture rather than a rapid test.

The failure rate of at-home tests is as much associated with product misuse (including improper swabbing and testing outside of the window period) as the technical limitations of the tests themselves. It is for this reason that any positive, inconclusive, or suspicious negative result from an at-home test be followed up with an in-office test at your local clinic or doctor's office.