The time it takes to get results from a strep test varies depending on the specific type of diagnostic test used to detect Group A Streptococcus (GAS) bacteria. A quick, in-office result is possible, but a more definitive laboratory analysis requires a longer waiting period. This difference in turnaround time is due to the varying scientific methods employed. Understanding the timeline for each test helps manage expectations for diagnosis and treatment.
Duration of the Rapid Strep Test
The Rapid Strep Test (RST) provides the most immediate answer, designed to deliver results during a single patient visit. Sample collection is fast, requiring only a few seconds for a healthcare provider to swab the back of the throat and tonsils. This collection method is used for both rapid and traditional testing.
The RST is an antigen detection test, looking for specific antigens on the surface of the GAS bacteria. Results are typically available within 5 to 15 minutes, allowing for quick diagnosis and immediate treatment if positive. The test involves mixing the throat swab sample with a reagent that causes a visible reaction if GAS antigens are present.
A positive RST result is highly reliable due to the test’s high specificity (95% or greater). However, the RST has lower sensitivity (averaging about 85%). This means a positive result is almost certainly correct, but a negative result may be inaccurate, as the test can miss true infections. This limitation often necessitates a second, more accurate test.
The Timeline for Strep Culture Results
When the RST is negative, a throat culture is often performed as a follow-up, especially for children and adolescents. The culture is considered the gold standard for accuracy because it involves growing any bacteria present in the sample in a laboratory environment. This method ensures that even low concentrations of bacteria are detected, compensating for the RST’s lower sensitivity.
The primary limitation of the throat culture is the time required for the bacteria to multiply sufficiently to be identified. The swab is streaked onto a specialized growth medium and then incubated. This necessary growth time means definitive results are not available for 24 to 48 hours.
This extended timeline is a trade-off for the culture’s superior accuracy, allowing it to catch false negative results from the rapid test. The culture is important in pediatric cases because untreated strep throat carries a risk of developing serious complications, such as rheumatic fever.
Time to Contagion Relief and Recovery
Once a positive diagnosis is made and antibiotic treatment begins, antibiotics quickly kill the Group A Streptococcus bacteria, significantly reducing transmission risk. A patient is typically no longer considered contagious after being on antibiotics for a full 24 hours.
Symptom improvement usually follows shortly after treatment initiation, with most patients beginning to feel better within one to two days. Throat pain, fever, and discomfort should start to noticeably lessen within 24 to 48 hours of taking the medication. If symptoms do not improve after 48 hours, a re-evaluation by a healthcare provider may be necessary.
It is important to complete the full 10-day course of antibiotics, even with rapid symptom relief. Stopping the medication early, even if feeling well, can lead to the infection returning and increases the risk of developing complications. The full regimen ensures all the bacteria are eradicated from the system.