Positive Rapid Antigen Detection Test Research Articles

A single-center experience on long-term clinical performance of a rapid SARS-CoV-2 Antigen Detection Test, STANDARD Q COVID-19 Ag Test

The COVID-19 pandemic in Korea has dynamically changed with the occurrence of more easily transmissible variants. A rapid and reliable diagnostic tool for detection of SARS-CoV-2 is needed. While RT-PCR is currently the gold standard for detecting SARS-CoV-2, the procedure is time-consuming and requires expert technicians. The rapid antigen detection test (RADT) was approved as a confirmatory test on 14 March 2022 due to rapid dissemination of the Omicron variant. The benefits of the RADT are speed, simplicity, and point-of-care feasibility. The aim of our study was to evaluate the clinical performance of RADT compared to RT-PCR in a single center over 15 months, fully covering the SARS-CoV-2 ‘Variants of Concern (VOC).’ A total of 14,194 cases was simultaneously tested by RT-PCR and RADT from January 2021 to March 2022 in Gangnam Severance Hospital and were retrospectively reviewed. PowerChek SARS-CoV-2, Influenza A&B Multiplex Real-time PCR Kit, and STANDARD Q COVID-19 Ag Test were used. Positive rates, sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) were estimated for five periods (3 months/period). Receiver operator characteristic curve (ROC) analysis was performed, and Spearman’s rank test assessed the correlation between RT-PCR Ct values and semi-quantitative RADT results. The overall positive rate of RT-PCR was 4.64%. The overall sensitivity and specificity were 0.577 [95% confidence interval (CI) 0.539–0.614] and 0.991 [95% CI 0.989–0.993], respectively. ROC analysis resulted in an area under the curve of 0.786 (P < 0.0001, Yuden’s index = 0.568). The PCR positive rates were estimated as 0.11%, 0.71%, 4.51%, 2.02%, and 13.72%, and PPV was estimated as 0.045, 0.421, 0.951, 0.720, and 0.798 in Periods 1, 2, 3, 4, and 5, respectively. A significant and moderate negative correlation between PCR Ct values and semi-quantitative RADT results was observed (Spearman’s ρ = − 0.646, P < 0.0001). The RADT exhibited good performance in specimens with low Ct values (Ct ≤ 25.00) by RT-PCR. The PPV was significantly higher in Periods 3 and 5, which corresponds to rapid dissemination of the Delta and Omicron variants. The high PPV implies that individuals with a positive RADT result are very likely infected with SARS-CoV-2 and would require prompt quarantine rather than additional RT-PCR testing. The sensitivity of 0.577 indicates that RADT should not replace RT-PCR. Nonetheless, given the high PPV and the ability to track infected persons through rapid results, our findings suggest that RADT could play a significant role in control strategies for further SARS-CoV-2 variants.

Prevalence of Positive Rapid Antigen Detection Test for Group A Streptococcus Among Patients With Respiratory Symptoms in Eastern Province, Kingdom of Saudi Arabia

Prevalence of Positive Rapid Antigen Detection Test for Group A Streptococcus Among Patients With Respiratory Symptoms in Eastern Province, Kingdom of Saudi Arabia

The impact of rapid antigen detection test (RADT) for group A streptococcus on the antibiotic prescription: an observational study from a primary care setting in Lisbon

Introduction: Acute pharyngitis is a common diagnosis in primary care. Although viruses are the most common aetiology, antibiotic therapy is frequently prescribed. The inappropriate antibiotic prescription should be avoided to prevent antibiotic resistance. Many national and international guidelines recommend testing for group A streptococcus (GAS) before antibiotic treatment when clinical presentation suggests GAS infection. Aim: This study aims to describe the feasibility of the implementation of the rapid antigen detection test (RADT) in a primary care setting and its impact on antibiotic prescription. Secondary goals include the evaluation of possible associations between symptoms and RADT results. Methods: From October 2019 to March 2020, patients presenting with acute pharyngitis at USF do Parque were eligible. A questionnaire was applied to divide the individuals into four different groups (clearly viral, probably viral, diagnostic doubt, and probably bacterial), and to assess the previous intention to prescribe antibiotics. We applied 136 questionnaires and performed 133 RADT. Nursing staff classified the specimen collection process and result from interpretation according to its difficulty. The proportion of antibiotics avoided was estimated as the number of times physicians changed their intended antibiotic prescription following a negative RADT result. Results: Among the tests performed, 97.7% were easy to interpret. Without RADT, 45 patients were going to be prescribed an antibiotic. After the test result, 27 antibiotic prescriptions were avoided. Tonsil hypertrophy, palatal petechiae, and fever increased the odds of a positive RADT result. Cough was associated with a negative RADT result. Conclusions: This study showed that RADT is easy to implement and contributed to appropriate antibiotic prescription. Tonsil hypertrophy, palatal petechiae, and fever were significantly associated with a positive RADT result, and cough was associated with a negative RADT result. Primary care centers would benefit from having RADT available when there is strong suspicion or doubt of bacterial pharyngitis.

Agreement between rapid antigen detection test and culture for group A streptococcus in patients recently treated for pharyngotonsillitis - a prospective observational study in primary care

Objective The aim was to compare rapid antigen detection test (RADT) and throat culture for group A streptococci (GAS) among patients recently treated with penicillin V for GAS pharyngotonsillitis. Design and setting The study was a secondary analysis within a randomized controlled trial comparing 5 versus 10 days of penicillin V for GAS pharyngotonsillitis. Patients were recruited at 17 primary health care centres in Sweden. Subjects We included 316 patients ≥ 6 years of age, having 3–4 Centor criteria, a positive RADT and a positive throat culture for GAS at inclusion, and also having a RADT and throat culture for GAS taken at a follow-up visit within 21 days. Main outcome measures RADT and conventional throat culture for GAS. Results This prospective study showed 91% agreement between RADT and culture at follow-up within 21 days. Only 3/316 participants had negative RADT with a positive throat culture for GAS at follow-up, and 27/316 patients with positive RADT had a negative culture for GAS. Log rank test did not reveal any difference in the decline over time of positive tests between RADT and throat culture (p = 0.24). Agreement between RADT and throat culture for GAS at the follow-up was not associated with treatment duration, number of days from inclusion until follow-up, throat symptoms at follow-up, gender, or age. Conclusion RADT and culture for GAS agreed to a high extent also after recent penicillin V treatment. RADT for GAS means a low risk for missing the presence of GAS. KEY POINTS Testing for group A streptococci (GAS) before antibiotic treatment can reduce antibiotic prescription for pharyngotonsillitis. It has been proposed that rapid antigen detection tests (RADT) for group A streptococci after recent penicillin V treatment may be falsely positive due to possible persisting antigens from non-viable bacteria. The decline of the presence of GAS was similar between RADT and conventional throat culture in patients who had recently completed penicillin V treatment for GAS pharyngotonsillitis RADT for GAS is useful in identifying the presence of GAS after recent penicillin V treatment

Clinical course of pharyngotonsillitis with group A streptococcus treated with different penicillin V strategies, divided in groups of Centor Score 3 and 4: a prospective study in primary care

BackgroundSore throat is a common reason for prescribing antibiotics in primary care, and 10 days of treatment is recommended for patients with pharyngotonsillitis with group A streptococcus (GAS). Our group recently showed that penicillin V (PcV) four times daily for 5 days was non-inferior in clinical outcome to PcV three times daily for 10 days. This study compares duration, intensity of symptoms, and side effects in patients with a Centor Score (CS) of 3 or 4 respectively, after treatment with PcV for 5 or 10 days and evaluates whether all patients with pharyngotonsillitis with a CS of 3 or 4 should be treated for 5 days or if severity of symptoms or CS suggest a longer treatment period.MethodData on symptoms and recovery from patient diaries from 433 patients included in a RCT comparing PcV 800 mg × 4 for 5 days or PcV 1 g × 3 for 10 days was used. Patients six years and older with CS-3 or CS-4 and positive rapid antigen detection test for GAS-infection were grouped based on CS and randomized treatment. Comparisons for categorical variables were made with Pearson’s chi-squared test or Fisher’s exact test. Continuous variables were compared with the Mann–Whitney U test.ResultsPatients with CS-3 as well as patients with CS-4 who received PcV 800 mg × 4 for 5 days self-reported that they recovered earlier compared to patients with CS-3 or CS-4 who received treatment with PcV 1 g × 3 for 10 days. In addition, the throat pain as single symptom was relieved 1 day earlier in patients with CS-4 and 5 days of treatment compared to patients with CS-4 and 10 days of treatment. No differences in side effects between the groups were found.ConclusionIntense treatment with PcV four times a day for 5 days seems clinically beneficial and strengthens the suggestion that the 4-dose regimen with 800 mg PcV for 5 days may be the future treatment strategy for GAS positive pharyngotonsillitis irrespectively of CS-3 or CS-4.Trail registration ClinicalTrials.gov ID: NCT02712307 (3 April 2016).

Assessment of Pharyngitis Management at a University Student Health Services Clinic

Objective: The objective of this study was to assess the management of students presenting with pharyngitis to a university health clinic. Methods: This was a retrospective cohort study. Electronic medical records of undergraduate students presenting to a university health clinic from January 1, 2012, through December 31, 2014, with complaints of sore throat and a diagnosis code for pharyngitis, tonsillitis, or sore throat were reviewed. Results: Records of 241 patients were screened and 197 patients were included. A rapid antigen detection test (RADT) was obtained in 145 (73.6%) patients. The incidence of group A streptococci (GAS) and non-GAS were 15.2% (30/197) and 10.1% (21/197), respectively. All patients with a positive RADT were prescribed antibiotics, with 13 (46.4%) receiving amoxicillin. Overall, 129 (65%) patients received an antibiotic prescription. Conclusion: Management of pharyngitis at the clinic appears inconsistent with current guidelines. Approximately 2 of every 3 students were prescribed an antibiotic with no clear indication.

Rapid strep testing in children with recently treated streptococcal pharyngitis.

ImportanceThe use of the rapid antigen‐detection test (RADT) has become the standard of care in the early diagnosis of group A beta‐hemolytic Streptococcus (GAS) pharyngitis. Concern has been expressed over increased false positives when the child had been treated recently for GAS pharyngitis, resulting in over use of antibiotics.ObjectiveTo determine if the false positive rate for RADT is increased in children recently treated for GAS pharyngitis.MethodsWe conducted a prospective study to evaluate 300 children from a private practice with acute pharyngitis who were treated for GAS pharyngitis within the preceding 28 days (study group) compared to 306 children of comparable age who had not been previously treated (control group). RADT and throat culture were performed on all children presenting with signs and symptoms of acute pharyngitis. The false positive and false negative rates were determined and compared in both groups.ResultsThe false positive rate of 11.5% (23/200) in the study group was significantly higher than the false positive rate of 0 in the control group. False positives were more likely to occur in younger children.InterpretationThese data would indicate that while RADT is reliable in most children, it can lead to over treatment in children who have been recently treated for GAS. In children treated in the preceding 28 days for GAS pharyngitis, the presence of infection should be determined with a throat culture only. Treatment based on a positive RADT should be reserved for children not recently treated for GAS pharyngitis.

A Reappraisal of the Minimum Duration of Antibiotic Treatment Before Approval of Return to School for Children With Streptococcal Pharyngitis.

To determine whether a single dose of amoxicillin administered to a symptomatic child with confirmed strep throat might allow the child to return to school as little as 12 hours later. We enrolled 111 evaluable children with sore throat plus a positive streptococcal rapid antigen detection test (RADT) as well as a positive result for group A Streptococci (GAS). After throat swab specimens were obtained, all participants received a single dose of amoxicillin (50 mg/kg). Twelve to 23 hours after the first dose of amoxicillin, all participants returned in the morning of day 2 for a second throat swab specimen. At the day 2 visit, a nurse or medical assistant obtained an interval history, tympanic membrane temperature, and a pediatrician or nurse practitioner examined the oropharynx. On the morning of day 2, only 10 of 111 participants continued to have a positive RADT result, confirmed by overnight throat culture. GAS were not detectable on the day 2 throat specimen by RADT and also by culture in 91% of the study participants (confidence interval: 86-96%). Seven of 10 failures had a marked decrease in number of β-hemolytic colonies, which were 3+ to 4+ on the initial overnight culture plate and decreased to 1+ on the follow-up (obtained on day 2) throat culture plate. Two participants continued to have 3+ or 4+ GAS after incubation of the second throat culture specimen. Even in the late afternoon, a full dose of amoxicillin (50 mg/kg) administered after notification of positive RADT results for GAS resulted in nondetection of GAS in 91% of children the next morning. All children treated with amoxicillin for "strep throat" by 5 PM of day 1 may, if afebrile and improved, attend school on day 2.

Clinical Evaluation of Macrolide-resistant Mycoplasma pneumoniae Infections in Pediatric Japanese Patients

Background: In recent years, an increase in Mycoplasma pneumonia e infections among children has become a social issue in Japan. Methods: During a 2-year collection period (2011-2012), we evaluated trends during the first and second halves of both years. Only patients with positive rapid antigen detection test results (ImmunoCard Mycoplasma : Meridian Bioscience, Inc Cincinnati, OH, USA) were included. The evaluation items included the patient number, sex, radiography findings, white blood cell (WBC) count, C-reactive protein (CRP) level, and clinical macrolide-resistance rate. Results: The patient number increased significantly during the latter halves of the years. The macrolide-resistance rate also increased during the same periods. A similar trend was observed with respect to radiography findings but not with respect to the WBC count and CRP level. Conclusions: It is important to monitor the macrolide-resistance trends in case of Mycoplasma pneumoniae infections in children.

Rapid antigen detection testing in diagnosing group A β-hemolytic streptococcal pharyngitis

Group A β-hemolytic streptococcus (GABHS) is the most common bacterial cause of acute pharyngitis. Clinical criteria alone are not reliable enough to diagnose GABHS pharyngitis. Microbiological-testing is required for correct diagnosis. Although a throat swab culture remains the gold standard for documenting the presence of GABHS, a significant disadvantage of the culture is the delayed time of 1–2 days to obtain results. Most rapid antigen detection tests can provide results in less than 15 min. Rapid identification and treatment of patients with GABHS pharyngitis can reduce the risk of the spread of disease, may shorten the duration of symptoms, decrease the incidence of suppurative complications, decrease the amount of time lost from school/work, decrease the inappropriate use of antibiotics, reduce patient/parent dissatisfaction and alleviate the need for costly follow-up visits. All rapid antigen detection tests involve extraction of the group-specific carbohydrate antigen from the GABHS cell wall and identification of the antigen by an immunological reaction. There are numerous rapid antigen detection testing methods, namely latex agglutination, enzyme immunoassay, optical immunoassay, chemiluminescent DNA probes and PCR methods. Most of the rapid antigen detection tests that are currently in use have an excellent specificity of greater than 95% and a sensitivity of greater than or equal to 90%. Owing to the high specificity of the rapid antigen detection tests, a positive rapid antigen detection test is accepted as adequate for the diagnosis of GABHS pharyngitis. Conversely, confirmation of a negative antigen detection test with a throat culture result is necessary, unless the physician has ascertained in his/her practice that the sensitivity of the rapid antigen test used is comparable with that of a throat culture.

Relationship Between the Clinical Likelihood of Group A Streptococcal Pharyngitis and the Sensitivity of a Rapid Antigen-Detection Test in a Pediatric Practice

The sensitivity of a rapid antigen-detection test (RADT) for group A streptococcal (GAS) pharyngitis is critical to whether the test is cost-effective and to whether a confirmatory throat culture is needed. We evaluated a second-generation RADT to determine if its sensitivity varies across the broad clinical spectrum of patients tested for GAS in pediatric outpatient practice. We used laboratory logbooks from a single pediatric clinic to identify 1184 consecutive patient visits at which an RADT was performed. In a blinded chart review, we calculated McIsaac scores to separately estimate the pretest clinical likelihood of GAS pharyngitis for visits at which the RADT result was positive (n = 384) and for visits at which the result proved to be false-negative (n = 65). Positive RADT results were assumed to be true positives, and test sensitivity was estimated by dividing the number of positive results by the sum of positives and false-negatives. As the clinical likelihood of GAS increased, there were stepwise increases in RADT sensitivity (from 0.67 to 0.88). Sensitivity was low (0.73; 95% confidence interval [CI]: 0.62-0.86) in patients clinically unlikely to have GAS (McIsaac score < or =2) and high (0.94; 95% CI: 0.89-0.99) in patients <15 years old who had tonsillar exudate and no cough. False-negative RADT results were associated with lighter growth of GAS than found on specimens obtained from a random sample of clinic patients who had only primary throat cultures ordered. For pediatric patients who are clinically unlikely to have GAS pharyngitis, as indicated by a McIsaac score < or =2, the sensitivity of a second-generation RADT may drop below thresholds reported for cost-effectiveness. For children who have tonsillar exudate and no cough, the test may be sensitive enough to meet current pediatric practice guidelines for stand-alone testing.

Recurrent group A streptococcal tonsillopharyngitis.

To examine the epidemiology and treatment of group A beta-hemolytic streptococcal (GABHS) recurrent tonsillopharyngitis in private pediatric practice. This was a retrospective chart review study covering the time span 1975 to 1996 involving 2140 GABHS episodes. Diagnosis was based on acute clinical symptoms and laboratory confirmation (throat culture or positive rapid antigen detection test) of GABHS. Eighty percent (n=1721) of the episodes evaluated were treated with penicillin or amoxicillin; 352 (20.5%) of these were followed by a recurrence within 30 days and 519 (30.2%) within 60 days. GABHS recurrences within 30 days after penicillin/amoxicillin treatment rose from 9% in 1975 to 1979 to 25.9% in 1980 to 1984, 24.2% in 1985 to 1989, 22.4% in 1990 to 1994 and 25.9% in 1995 to 1996 (P < 0.02); 53.4% of the recurrences were associated with symptoms and signs of GABHS tonsillopharyngitis, 9.9% were asymptomatic and 36.7% could not be classified. Recurrences within 60 days after penicillin/ amoxicillin treatment rose from 10.7% in 1975 to 1979 to 38.7% in 1980 to 1984, 39.0% in 1985 to 1989, 31.7% in 1990 to 1994 and 37.5% in 1995 to 1996 (P < 0.001). Recurrent GABHS infections occurred more frequently in younger children (1 to 8 years of age, 21.3% recurrence rate) than in adolescents (13 to 19 years, 5% recurrence rate; P=0.002). Recurrences within 30 days occurred more often after therapy with penicillin (21.8% of 1581 episodes) than with cephalosporins (8.6% of 254 episodes) (P < 0.0001) or with macrolides (14.0% of 143 episodes, P=0.04). Recurrence rates were unaffected by patient gender or season of the year. Recurrent GABHS infections occur more frequently in the 1990s than the 1970s, occur more frequently in children younger than 8 years of age than in adolescents and occur more frequently after penicillin treatment than with alternative antibiotic therapy.