Rapid Antigen Detection Test Results 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.

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.

Diagnostic Impact of Clinical Manifestations of Group A Streptococcal Pharyngitis.

This study aims to identify the clinical characteristics for diagnosing streptococcal pharyngitis. The correlation between eighteen clinical manifestations and rapid antigen detection test results was analyzed. Among 205 patients, five clinical manifestations, pharyngeal hemorrhage (odds ratio [OR] = 11.85), palatal hemorrhage (OR = 9.32), tonsillar swelling (OR = 4.37), rash (OR = 3.02), and enlarged cervical nodes (OR = 1.91), were significantly correlated with group A Streptococcus (GAS) pharyngitis. Traditional indicators such as fever, pharyngeal redness, acute onset, headache, rhinorrhea, cough, tonsillar exudate, and cervical tenderness were not statistically related to GAS pharyngitis. Therefore, physicians should be cautious in using these traditional indicators.

Diagnosis and antibiotic treatment of group a streptococcal pharyngitis in children in a primary care setting: impact of point-of-care polymerase chain reaction

BackgroundTo compare the sensitivity and specificity of the recommended 2-step rapid antigen detection test (RADT) with confirmatory culture vs the point-of-care (POC) polymerase chain reaction (PCR) Roche cobas® Liat® Strep A test for detection of group A Streptococcus (GAS) in pediatric patients with pharyngitis, and to investigate the impact of these tests on antibiotic use in a large pediatric clinic.MethodsThis prospective, open-label study was conducted at a single site during fall/winter 2016–2017. A total of 275 patients aged 3 to 18 years with symptoms of pharyngitis had a throat-swab specimen analyzed using RADT, POC PCR, and culture. The sensitivity, specificity, and percentage agreement (95% CI) between assays and a laboratory-based nucleic acid amplification test were calculated. DNA sequencing was used to adjudicate discrepancies. The RADT or POC PCR result was provided to clinicians on alternating weeks to compare the impact on antibiotic use.ResultsA total of 255 samples were evaluated; 110 (43.1%) were GAS positive. Sensitivities (95% CI) for POC PCR, RADT, and culture were 95.5% (89.7–98.5%), 85.5% (77.5–1.5%), and 71.8% (62.4–80.0%), respectively. Specificities (95% CI) for POC PCR, RADT, and culture were 99.3% (96.2–99.98%), 93.7% (88.5–97.1%), and 100% (97.5–100%), respectively. Compared with RADT, POC PCR resulted in significantly greater appropriate antibiotic use (97.1% vs 87.5%; P = .0065).ConclusionUnder real-world conditions, RADT results were less specific and culture results were less sensitive than found in established literature and led to increased rates of inappropriate antibiotic use. POC PCR had high sensitivity and specificity and rapid turnaround times, and led to more appropriate antibiotic use.Trial registrationID number ISRCTN84562679. Registered October 162,018, retrospectively registered.

Caution Needed: Molecular Diagnosis of Pediatric Group A Streptococcal Pharyngitis.

Among throat swabs processed in the microbiology laboratory as back-up for negative rapid antigen detection test results, we found a significant increase in the proportion that tested positive for group A streptococci after changing from throat culture to a molecular test.For group A streptococcus testing, our hospital laboratory replaced throat cultures with a stand-alone molecular diagnostic test that takes no more than 1 hour to perform. The prevalence of positive laboratory test results increased significantly (P < .0001) after the change to molecular testing, probably because of the extreme sensitivity of the molecular test.

Usefulness of Centor Score to Diagnosis of Group a Streptococcal Pharyngitis and Decision Making of Antibiotics Use

Background and Objectives This study aims to verify the usefulness of Centor scores to diagnose the Group A Streptococcal pharyngitis. Subjects and Method The subjects of this study were 379 patients who had been examined by the rapid antigen detection test (RADT) for Group A Streptococcus. We analyzed their medical records and laboratory test results retrospectively and compared the results of Centor symptom scores with those of RADT. Then we analyzed the association of RADT, the Centor score and the laboratory test results statistically. Results There were no correlation between the RADT results and fever, cough, tonsillar enlargement, nasal symptoms, myalgia or chilling (p＞0.05). In the RADT positive group, there were more patients with tonsillar exudate, neck lymph node enlargement, tenderness and pharyngeal abscess formation significantly (p＜0.05). The Centor score and C-reactive protein were significantly higher in the RADT positive group (p＜0.05). Conclusion The results of this study suggest that Centor symptom scores can be used to determine which antibiotics to use. The Centor score system can help reduce medical costs and detect the problematic Group A Streptococcal pharyngitis. Key words: Centor score ㆍ Pharyngitis ㆍ Rapid antigen detection test ㆍ Streptococcus pyogenes

The Effect of Rapid Antigen Detection Test on Antibiotic Prescription Decision of Clinicians and Reducing Antibiotic Costs in Children with Acute Pharyngitis.

We aimed to investigate the effect of rapid antigen detection test (RADT) in the diagnosis of streptococcal pharyngitis, its impact on antibiotic prescription decision of pediatricians and influence on reduction of antibiotic treatment costs in children with pharyngitis. The study group consisted of 223 patients who were diagnosed with pharyngitis by pediatricians. The sensitivity and specificity of RADT were 92.1% (95% Cl: 78.6-98.3%) and 97.3% (95% Cl: 93.8-99.1%), respectively. In the first assessment, before performing RADT, pediatricians decided to prescribe antibiotics for 178 (79.8%) patients with pharyngitis. After learning RADT results, pediatricians finally decided to prescribe antibiotics for 83 (37.2%) patients with pharyngitis, and antibiotic prescription decreased by 42.6%. Antibiotic costs in non-Group A streptococcus pharyngitis, Group A streptococcus pharyngitis and all subjects groups decreased by 80.8%, 48%, and 76.4%, respectively. Performing RADT in children with pharyngitis has an important impact on treatment decision of clinicians, reduction of unnecessary antibiotic prescriptions and antibiotic costs.

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.

Empirical validation of Polish guidelines for the management of acute streptococcal pharyngitis in children

ObjectiveGroup A Streptococcus (GAS) pharyngitis is currently the only commonly occurring form of acute pharyngitis for which antibiotic therapy is definitely indicated. Polish guidelines advocate the use of modified Centor score (MCS) to assess the probability of GAS pharyngitis. They advise performing throat culture or rapid antigen detection test (RADT) in children with score 2–3 in MCS and treating with antibiotic only those in whom GAS was detected. Negative RADT results should be confirmed by culture. In children with score 4, the guidelines allow to introduce empiric antibiotic therapy. Phenoxymethyl penicillin is recommended as a drug of choice to treat GAS pharyngitis. The aim of our study was to evaluate the accuracy of strategy recommended by Polish guidelines in identifying those children with acute pharyngitis who require antibiotic treatment. Hence, diagnostic values of score 4 in MCS and RADT were assessed using throat culture as a reference standard. Phenoxymethyl penicillin efficacy in GAS eradication and prevention of post-streptococcal complications were estimated as well. MethodsNinety children between 2 and 15 years of age with acute pharyngitis symptoms suggesting GAS etiology (MCS≥2), participated in our study. At the initial visit MCS was evaluated and two throat swabs were collected to perform RADT and culture. In children with GAS pharyngitis treated with penicillin, microbiological cure was assessed by performing two control throat cultures. Next, children were under observation for 3 months. ResultsPositive predictive value of score 4 in MCS turned out to be 48.05% (95% CI: 36.5–59.7%). RADT sensitivity, specificity and diagnostic accuracy proved to be 100%, 96%, and 98%, respectively. GAS eradication rate in children treated with penicillin turned out to be 92.5%. No post-streptococcal sequelae occurred in any child in 3-month observation. ConclusionsEmpiric antibiotic therapy in children with score 4 in MCS will result in significant overtreatment of those with nonstreptococcal pharyngitis. New generation RADT diagnostic value in GAS detection proved to be equivalent to that of culture, which obviates the need of backup culture in children with negative RADT results. Phenoxymethyl penicillin revealed high eradication efficacy and proved to prevent post-streptococcal sequelae in children with acute GAS pharyngitis.

Pragmatic Scoring System for Pharyngitis in Low-Resource Settings

Our objective was to develop an easy, safe, pragmatic, clinical scoring system that would allow decreases in unnecessary treatment with antimicrobial agents in low-resource settings. Children with pharyngitis were enrolled prospectively from 2 public hospitals and 1 medical unit in Brasilia, Brazil, over 17 months. Attending clinicians completed a questionnaire and a previously published scoring system for pharyngitis before performing throat swabs and group A streptococcus (GAS) rapid antigen-detection tests. Data from this study were added to those collected in 2004, to assess the performance of each item of the scoring system. The performance of the new clinical decision rule was determined with a receiver operating characteristic curve. The final outcome of the model was assessed on the basis of sensitivity, specificity, and positive likelihood ratio for non-GAS infections with the clinical approach, compared with throat culture or rapid antigen-detection test results. A total of 576 children were included, among whom 400 had non-GAS pharyngitis. The use of our new clinical decision rule would allow for 35% to 55% antibiotic reduction, with 88% specificity. This clinical decision rule could reduce unnecessary antibiotic treatment significantly in low-resource settings.

Prevalence of Group A b-Hemolytic Streptococcus Among Children with Tonsillopharyngitis in Kyrgyzstan: The Difficulty of Diagnostics and Therapy

Objective: Rheumatic fever (RF) is well known disease as a result of frequent complication of the group A b-hemolytic streptococcal (GABHS) tonsillopharyngitis, have noticeably grown for the last 15 years among young generation in the Kyrgyz Republic. It is important to hold a study about the prevalence of RF and GABHS and their susceptibility to antibiotics in the Kyrgyz Republic.Materials and Methods: We have studied 200 children with chronic tonsillopharyngitis at the National Center of Pediatrics and Child Surgery in Bishkek (the Kyrgyz Republic) from August till September 2008. 188 (48 out of them are with RF) out of total 200 children are Kyrgyz and 12 are Russian (2 out of them are with RF). 111 out of total are female (34 out of them are with RF) and 89 are male (17 out of them are with RF). The average age of the subjects is 10.9±6.0 (from 3 to 17 years old). The presence of GABHS was assessed using two ways: by the rapid antigen detection test (RADT) for outcrop of streptococcus antigen in smear from mucosal surface of tonsils, and by bacterial culture analysis (BA). RADT was used to determine its specificity and sensitivity in order to recommend practitioners its further wide use. Furthermore, the discovered culture of GABHS have been investigated on susceptibility to antibiotics by disc-diffusion method.Research Results: GABHS antigen was positive in 72 (36.0 %) subjects from RADT and in 80 (40.0%) subjects from BA out of 200 total subjects. In the patients with RF (n=51), GABHS was positive in 18 (35.2%) subjects by RADT and in 24 (47.0%) subjects by BA. In the subjects without RF (n=149), GABHS was positive in 54 (36.2%) subjects by RADT and in 56 (37.5%) by BA. Among 80 GABHS positive results sensitive to antibiotics were: to penicillin only 10 (12.5%), to ampicillin-29 (36.2%), to amoxicillin-36 (45.0%), to ceftriaxon - 31 (38.7%), to roxithromycin - 21 (26.2%), to erythromycin- 19 (23.7%). It is noted that 21 (26.2%) GABHS positive results were absolutely resistant for all these tested antibiotics. RADT showed that its specificity is 85% as well as its sensitivity is equal to 67.5%.Conclusion: In this study the sensitivity of RADT was low; therefore, the negative results of RADT don’t exclude presence of GABHS. High prevalence of GABHS antigen demonstrates not only in patients with RF, but also among healthy children (without RF) of the Kyrgyz Republic. The high prevalence of GABHS at children with RF (47.0%), probably, presents a low sensitivity to antibiotics and irregular secondary prophylaxis. Significant presence of GABHS among healthy children (37.5%) requires improvement of primary prevention to prevent further spread of RF and Rheumatic Heart Disease (RHD) in the country.

Antibiotic use in children is not influenced by the result of rapid antigen detection test for the respiratory syncytial virus

Background Rapid antigen detection test (RADT) for respiratory syncytial virus (RSV) is widely used in children hospitalized with acute respiratory tract infection (ARTI), but its influence on antibiotic (AB) use is uncertain. Objective To evaluate if confirmation of RSV infection by RADT modified AB use and elucidate others factors associated with the continuation of antibiotics. Study design Charts of children hospitalized with viral ARTI aged 0–35 months were reviewed. Modification of antibiotics according to RSV RADT results was compared using Kaplan–Meier estimates and multivariate Cox regression. Results Of children receiving antibiotics when the RSV RADT result was available, RSV RADT was positive in 144 and negative in 54. Positive RSV RADT results did not lead to modification of antibiotic use. Factors independently associated with cessation of intravenous antibiotics were age ≥ 3 months (HR 2.44 [1.41–4.21]) and absence of pneumonia (HR 1.50 [1.03–2.19]). Absence of otitis was associated with cessation of oral antibiotics (HR 9.16 [95% CI, 2.35–35.76]). Conclusion Confirmed presence of RSV by RADT did not influence antibiotic use in young children with ARTI. Except with pneumonia, the risk of bacterial superinfection of RSV infected children is minimal and confirmation of RSV infection should prompt treating physicians to interrupt antibiotics.

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.