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Accuracy of rapid strep testing in patients who have had recent streptococcal pharyngitis
Robert D Sheeler1, Margaret S Houston, Sharon Radke
1Department of Family Medicine, Mayo Clinic, Rochester, MN 55905, USA.
Background:
Some clinicians have questioned the accuracy of rapid diagnosis of group A streptococcal pharyngitis by commercial immunochemical antigen test kits in the setting of recent streptococcal pharyngitis, believing that the false-positive rate was increased because of presumed antigen persistence.
Methods:
We studied 443 patients--211 cases--who had clinical pharyngitis diagnosed as group A beta-hemolytic streptococcus infection in the past 28 days and compared them with 232 control patients who had symptoms of pharyngitis but no recent diagnosis of streptococcal pharyngitis. Our aim was narrowly focused to compare the rapid strep test with the culture method we used in our clinical practice.
Results:
We found that the rapid strep test in this setting showed no difference in specificity (0.96 vs 0.98); hence, the assertion that rapid antigen testing had higher false-positive rates in those with recent infection was not confirmed. We also found that in patients who had recent streptococcal pharyngitis, the rapid strep test appears to be more reliable (0.91 vs 0.70, P < .001) than in those patients who had not had recent streptococcal pharyngitis.
Conclusions:
The findings of this study indicate that the rapid strep test is both sensitive and specific in the setting of recent group A beta-hemolytic streptococcal pharyngitis, and its use might allow earlier treatment in this subgroup of patients.
Insights
Rapid strep tests are accurate for diagnosing group A streptococcal pharyngitis, even after a recent infection. These tests show reliable results, supporting earlier treatment for patients with recent streptococcal pharyngitis.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Diagnostics
Background:
- Clinicians question rapid strep test accuracy in patients with recent group A streptococcal pharyngitis due to concerns of antigen persistence.
- Previous beliefs suggested increased false-positive rates for rapid antigen detection tests in such cases.
Purpose of the Study:
- To evaluate the accuracy and reliability of rapid strep tests in diagnosing group A streptococcal pharyngitis in patients with a history of recent infection.
- To compare the performance of rapid antigen testing against culture methods in clinical practice.
Main Methods:
- A study involved 443 patients with clinical pharyngitis; 211 had a recent diagnosis of group A beta-hemolytic streptococcus infection within 28 days.
- 232 control patients with pharyngitis symptoms but no recent streptococcal diagnosis were included for comparison.
- The study focused on comparing rapid strep test results with the established culture method.
Main Results:
- The specificity of the rapid strep test showed no significant difference (0.96 vs 0.98) between groups, refuting claims of higher false-positive rates.
- Rapid strep tests demonstrated higher reliability in patients with recent streptococcal pharyngitis (0.91) compared to those without (0.70), with statistical significance (P < .001).
Conclusions:
- The rapid strep test is confirmed to be sensitive and specific for diagnosing group A beta-hemolytic streptococcal pharyngitis, even in patients with recent infections.
- The findings suggest that utilizing rapid strep tests may facilitate earlier treatment initiation for patients previously treated for streptococcal pharyngitis.