Strep throat is a common bacterial infection caused by Group A Streptococcus, which affects the tonsils and pharynx. An accurate diagnosis allows for prompt antibiotic treatment, which is important because untreated strep throat carries the risk of serious complications, such as acute rheumatic fever. The diagnostic timeline involves several steps, beginning with the healthcare provider’s initial evaluation to determine if testing is necessary.
Clinical Assessment Before Testing
The clinical assessment involves the healthcare provider evaluating a patient’s symptoms to gauge the likelihood of a strep infection. This initial consultation typically takes only a few minutes and focuses on signs pointing toward a bacterial cause rather than a viral one. Providers often use scoring systems, such as the modified Centor criteria, to guide their decision-making.
These criteria assign points for symptoms like fever, white patches or pus on the tonsils (exudates), and swollen lymph nodes in the neck. Points are also given for the absence of a cough, which is usually associated with viral illness. A higher score suggests a greater probability of strep throat, indicating that a diagnostic test should be performed. If the assessment suggests a very low probability of strep, testing may not be warranted.
Rapid Strep Testing
If the clinical assessment suggests a moderate or high probability of strep throat, the next step is typically the Rapid Antigen Detection Test (RADT). The RADT detects specific proteins, or antigens, on the surface of the Group A strep bacteria. Sample collection is fast, involving a sterile swab brushed across the back of the throat and tonsils, a process that takes only a few seconds.
The primary advantage of the RADT is the immediate turnaround time for results. Results are typically available within 5 to 10 minutes, though some tests may require up to 20 minutes to process. If the rapid test is positive, the diagnosis is confirmed immediately, allowing the healthcare provider to prescribe antibiotics right away.
Confirmatory Throat Culture
Despite the speed of the RADT, it has a lower sensitivity compared to traditional laboratory methods and can sometimes produce a false negative result. If the RADT is negative but the provider still suspects strep, especially in children and adolescents, a confirmatory throat culture is often performed. The sample for the culture is collected using the same throat swab technique.
The throat culture is a much longer process because the swab is sent to a laboratory and incubated. This incubation allows any bacteria present to multiply sufficiently for identification. Final results typically take between 24 and 48 hours to become available. This delay means the patient must wait one to two full days for a definitive diagnosis if the initial rapid test was negative.
Starting Treatment After Diagnosis
Once a positive diagnosis is confirmed, the final step is the initiation of antibiotic treatment. A prescription is usually provided immediately to begin the 10-day course of medication. Starting treatment promptly helps shorten the duration of symptoms, prevents the spread of infection, and reduces the risk of serious complications.
Most patients notice significant improvement in their sore throat and fever within 24 to 48 hours of taking the first dose. Although symptoms improve quickly, it is important to complete the entire course of medication as prescribed. Completing the full course ensures all bacteria are eliminated, preventing a relapse and minimizing the chance of developing long-term health issues.