[Validation of a rapid antigenic test in the diagnosis of pharyngitis caused by group a beta-haemolytic Streptococcus]

Knowledge, Attitude, and Practice of House Officers to the Diagnosis and Management of Bacterial Pharyngitis: A Multicenter Cross-Sectional Study

BACKGROUND

Pharyngitis is one of the most common clinical presentations in pediatric clinics. Streptococcal pharyngitis reaches a nadir in the early school years, and it is vital to diagnose it early to avoid the serious complications that can arise from improper treatment, such as acute rheumatic fever and rheumatic heart disease.

MATERIALS AND METHODS

This is a cross-sectional multicenter study of medical house officers conducted from January to February 2018.

RESULTS

This study surveyed 135 house officers at Khartoum's primary health centers and hospitals. Most of the respondents were males (76/135; 56%). Most of the house officers reported seeing patients with throat complaints 1-2 times per week (58/135; 43%). The most common complication was acute rheumatic fever (65/135; 48%). Out of all the criteria of a Group A beta-hemolytic streptococcus (GAS) pharyngitis diagnosis, absence of cough and tender lymph nodes were the least recognized by house officers, i.e. 11.9% (16/135) and 45.2% (61/135), respectively. Only (4/135) 3% knew the full criteria for diagnosing bacterial pharyngitis. Throat culture was the most commonly used lab test to diagnose bacterial pharyngitis (115/135; 85.2%). The majority of participants did not recognize an IM injection of benzathine penicillin G as the first-line management of bacterial pharyngitis (101/135; 74.8%). The participants had moderate knowledge (93/135; 68.9%). Those with poor knowledge also happened to have poor practice (p = 0.009). Those who see more cases per week were also more likely to have good knowledge (p = 0.000). House officers with a moderate attitude constituted about 48.9% (66/135) of the whole sample. The most often prescribed medication was amoxicillin-clavulanic acid for one week (53/135; 39.3%). The practice score was associated with a lower knowledge (p = 0.009). Only 20.7% (28/135) of the participants in our study were adherent to the use of benzathine penicillin G as the first-line management of bacterial pharyngitis.

CONCLUSION

House officers had poor-to-moderate knowledge regarding the diagnosis and management of bacterial pharyngitis, especially in regard to what antibiotic to use. However, their fear of antibiotic resistance was a good behavior.

[Introduction of rapid streptococcal antigen test: can its use improve adherence to antibiotic therapy?]

OBJECTIVE

To evaluate the influence of the result of a rapid streptococcal antigen test in paediatric pharyngotonsillitis infections, in terms of improvement of antibiotic therapy adherence.

DESIGN

Randomized community clinical trial with two study groups.

LOCATION

Primary Care Centers in Central Catalonia.

PARTICIPANTS

Patients aged from 3 to 15 years, who were attended at paediatric consultations on suspicion of pharyngotonsillitis caused by an infection between November 2010 and February 2011 (both included), were included in the study on a consecutive basis. 557 patients met the inclusion criteria and 519 were evaluated.

INTERVENTION

The control group received the usual diagnostic-therapeutic algorithm. Rapid streptococcal antigen test was additionally performed to experimental group participants and it was indicated the more convenient treatment.

MAIN MEASUREMENTS

Antibiotic adherence, non-adherence causes and socio-demographic risk factors were evaluated via telephone survey.

RESULTS

Antibiotics were prescribed to 65.6% and paediatricians of the control group were more likely to prescribe antibiotic than the ones in the intervention group (88.5% vs 45.5%, p< 0.0001). 64.8% followed doctor's treatment orders, being failure following medication scheduling the main cause of non-adherence (25.6%). Medication adherence was higher in the experimental group (68%) than in the control group (62.9%) but no significant differences were found.

CONCLUSION

Rapid strep test, complementing the use of Centor Criteria avoids unnecessary antibiotics prescriptions, but had not been proven to be effective in increasing medication adherence.

Signs and symptoms of Group A versus Non-Group A strep throat: A meta-analysis

INTRODUCTION

Both non-Group A streptococcal (non-GAS) pharyngitis and Group A streptococcal (GAS) pharyngitis are commonly found in patients with sore throat. It is not known whether or not they present with similar signs and symptoms compared to patients with non-streptococcal pharyngitis.

METHODS

MEDLINE was searched for prospective studies that reported throat culture for both GAS and non-GAS as a reference standard, and reported at least one sign, symptom, or the Centor score. Summary estimates of sensitivity, specificity, likelihood ratios (LR+ and LR-), and diagnostic odds ratios (DOR) were calculated using a bivariate random effects model. Summary receiver operating characteristic (ROC) curves were created for key signs and symptoms.

RESULTS

Eight studies met our inclusion criteria. Tonsillar exudate had the highest LR+ for both GAS and non-GAS pharyngitis (1.53 versus 1.71). The confidence intervals of sensitivity, LR+, LR-, and DOR for all signs, symptoms, and the Centor score between two groups overlapped, with the relative difference between sensitivities within 15% for arthralgia or myalgia, fever, injected throat, tonsillar enlargement, and tonsillar exudate. Larger differences in sensitivities were observed for sore throat, cervical adenopathy, and lack of a cough, although the difference for lack of a cough largely due to a single outlier.

DISCUSSION

Signs and symptoms of patients with GAS and non-GAS pharyngitis are generally similar. No signs or symptoms clearly distinguish GAS from non-GAS infection. Further work is needed to determine whether Group C streptococcus is a pathogen that should be treated.

Rapid antigen detection test for group A streptococcus in children with pharyngitis

BACKGROUND

Group A streptococcus (GAS) accounts for 20% to 40% of cases of pharyngitis in children; the remaining cases are caused by viruses. Compared with throat culture, rapid antigen detection tests (RADTs) offer diagnosis at the point of care (within five to 10 minutes).

OBJECTIVES

To determine the diagnostic accuracy of RADTs for diagnosing GAS in children with pharyngitis. To assess the relative diagnostic accuracy of the two major types of RADTs (enzyme immunoassays (EIA) and optical immunoassays (OIA)) by indirect and direct comparison.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE, Web of Science, CDSR, DARE, MEDION and TRIP (January 1980 to July 2015). We also conducted related citations tracking via PubMed, handsearched reference lists of included studies and relevant review articles, and screened all articles citing included studies via Google Scholar.

SELECTION CRITERIA

We included studies that compared RADT for GAS pharyngitis with throat culture on a blood agar plate in a microbiology laboratory in children seen in ambulatory care.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts for relevance, assessed full texts for inclusion, and carried out data extraction and quality assessment using the QUADAS-2 tool. We used bivariate meta-analysis to estimate summary sensitivity and specificity, and to investigate heterogeneity across studies. We compared the accuracy of EIA and OIA tests using indirect and direct evidence.

MAIN RESULTS

We included 98 unique studies in the review (116 test evaluations; 101,121 participants). The overall methodological quality of included studies was poor, mainly because many studies were at high risk of bias regarding patient selection and the reference standard used (in 73% and 43% of test evaluations, respectively). In studies in which all participants underwent both RADT and throat culture (105 test evaluations; 58,244 participants; median prevalence of participants with GAS was 29.5%), RADT had a summary sensitivity of 85.6%; 95% confidence interval (CI) 83.3 to 87.6 and a summary specificity of 95.4%; 95% CI 94.5 to 96.2. There was substantial heterogeneity in sensitivity across studies; specificity was more stable. There was no evidence of a trade-off between sensitivity and specificity. Heterogeneity in accuracy was not explained by study-level characteristics such as whether an enrichment broth was used before plating, mean age and clinical severity of participants, and GAS prevalence. The sensitivity of EIA and OIA tests was comparable (summary sensitivity 85.4% versus 86.2%). Sensitivity analyses showed that summary estimates of sensitivity and specificity were stable in low risk of bias studies.

AUTHORS' CONCLUSIONS

In a population of 1000 children with a GAS prevalence of 30%, 43 patients with GAS will be missed. Whether or not RADT can be used as a stand-alone test to rule out GAS will depend mainly on the epidemiological context. The sensitivity of EIA and OIA tests seems comparable. RADT specificity is sufficiently high to ensure against unnecessary use of antibiotics. Based on these results, we would expect that amongst 100 children with strep throat, 86 would be correctly detected with the rapid test while 14 would be missed and not receive antibiotic treatment.

[Recommendations for management of acute pharyngitis in adults]

La faringoamigdalitis aguda (FAA) en el adulto es una de las enfermedades infecciosas más comunes en la consulta del médico de familia. La etiología más frecuente es viral. Dentro de la etiología bacteriana, el principal agente responsable es Streptococcus pyogenes o estreptococo β-hemolítico del grupo A (EBHGA), causante del 5-30% de los casos. En el manejo diagnóstico, las escalas de valoración clínica para predecir la posible etiología bacteriana, son una buena ayuda para seleccionar a qué pacientes se deben practicar las técnicas de detección rápida de antígeno estreptocócico. Es conocido que, en general, sin estas técnicas se tiende al sobrediagnóstico de FAA estreptocócica, con la consiguiente prescripción innecesaria de antibióticos, muchas veces de amplio espectro. Así, con el manejo de las escalas y la técnica de diagnóstico rápido, elaboramos los algoritmos de manejo de la FAA. Los objetivos del tratamiento son acelerar la resolución de los síntomas, reducir el tiempo de contagio y prevenir las complicaciones supurativas locales y no supurativas. Los antibióticos de elección para el tratamiento de la FAA estreptocócica son penicilina y amoxicilina. La asociación de amoxicilina y clavulánico no está indicada en el tratamiento inicial en la infección aguda. Los macrólidos tampoco son un tratamiento de primera elección; su uso debe reservarse para pacientes con alergia a la penicilina. Es importante en nuestro país adecuar tanto el diagnóstico de la FAA bacteriana y la prescripción de antibióticos a la evidencia científica disponible. La implantación de protocolos de actuación en las farmacias comunitarias puede ser de utilidad para identificar y cribar los casos que no requieran tratamiento antibiótico.

[Recommendations for management of acute pharyngitis in adults]

Acute pharyngitis in adults is one of the most common infectious diseases seen in general practitioners' consultations. Viral aetiology is the most common. Among bacterial causes, the main agent is Streptococcus pyogenes or group A β-haemolytic streptococcus (GABHS), which causes 5%-30% of the episodes. In the diagnostic process, clinical assessment scales can help clinicians to better predict suspected bacterial aetiology by selecting patients who should undergo a rapid antigen detection test. If these techniques are not performed, an overdiagnosis of streptococcal pharyngitis often occurs, resulting in unnecessary prescriptions of antibiotics, most of which are broad spectrum. Consequently, management algorithms that include the use of predictive clinical rules and rapid tests have been set up. The aim of the treatment is speeding up symptom resolution, reducing the contagious time span and preventing local suppurative and non-suppurative complications. Penicillin and amoxicillin are the antibiotics of choice for the treatment of pharyngitis. The association of amoxicillin and clavulanate is not indicated as the initial treatment of acute infection. Neither are macrolides indicated as first-line therapy; they should be reserved for patients allergic to penicillin. The appropriate diagnosis of bacterial pharyngitis and proper use of antibiotics based on the scientific evidence available are crucial. Using management algorithms can be helpful in identifying and screening the cases that do not require antibiotic therapy.

[Recommendations for management of acute pharyngitis in adults]

La faringoamigdalitis aguda (FAA) en el adulto es una de las enfermedades infecciosas más comunes en la consulta del médico de familia. La etiología más frecuente es viral. Dentro de la etiología bacteriana, el principal agente responsable es Streptococcus pyogenes o estreptococo β-hemolítico del grupo A (EBHGA), causante del 5-30% de los casos. En el manejo diagnóstico, las escalas de valoración clínica para predecir la posible etiología bacteriana, son una buena ayuda para seleccionar a qué pacientes se deben practicar las técnicas de detección rápida de antígeno estreptocócico. Es conocido que, en general, sin estas técnicas se tiende al sobrediagnóstico de FAA estreptocócica, con la consiguiente prescripción innecesaria de antibióticos, muchas veces de amplio espectro. Así, con el manejo de las escalas y la técnica de diagnóstico rápido, elaboramos los algoritmos de manejo de la FAA. Los objetivos del tratamiento son acelerar la resolución de los síntomas, reducir el tiempo de contagio y prevenir las complicaciones supurativas locales y no supurativas. Los antibióticos de elección para el tratamiento de la FAA estreptocócica son penicilina y amoxicilina. La asociación de amoxicilina y clavulánico no está indicada en el tratamiento inicial en la infección aguda. Los macrólidos tampoco son un tratamiento de primera elección; su uso debe reservarse para pacientes con alergia a la penicilina. Es importante en nuestro país adecuar tanto el diagnóstico de la FAA bacteriana y la prescripción de antibióticos a la evidencia científica disponible. La implantación de protocolos de actuación en las farmacias comunitarias puede ser de utilidad para identificar y cribar los casos que no requieran tratamiento antibiótico.

Recommendations for management of acute pharyngitis in adults

Acute pharyngitis in adults is one of the most common infectious diseases seen in general practitioners' consultations. Viral aetiology is the most common. Among bacterial causes, the main agent is Streptococcus pyogenes or group A β-haemolytic streptococcus (GABHS), which causes 5%-30% of the episodes. In the diagnostic process, clinical assessment scales can help clinicians to better predict suspected bacterial aetiology by selecting patients who should undergo a rapid antigen detection test. If these techniques are not performed, an overdiagnosis of streptococcal pharyngitis often occurs, resulting in unnecessary prescriptions of antibiotics, most of which are broad spectrum. Consequently, management algorithms that include the use of predictive clinical rules and rapid tests have been set up. The aim of the treatment is speeding up symptom resolution, reducing the contagious time span and preventing local suppurative and non-suppurative complications. Penicillin and amoxicillin are the antibiotics of choice for the treatment of pharyngitis. The association of amoxicillin and clavulanate is not indicated as the initial treatment of acute infection. Neither are macrolides indicated as first-line therapy; they should be reserved for patients allergic to penicillin. The appropriate diagnosis of bacterial pharyngitis and proper use of antibiotics based on the scientific evidence available are crucial. Using management algorithms can be helpful in identifying and screening the cases that do not require antibiotic therapy.

Rapid antigen group A streptococcus test to diagnose pharyngitis: a systematic review and meta-analysis

Background

Pharyngitis management guidelines include estimates of the test characteristics of rapid antigen streptococcus tests (RAST) using a non-systematic approach.

Objective

To examine the sensitivity and specificity, and sources of variability, of RAST for diagnosing group A streptococcal (GAS) pharyngitis.

Data Sources

MEDLINE, Cochrane Reviews, Centre for Reviews and Dissemination, Scopus, SciELO, CINAHL, guidelines, 2000–2012.

Study Selection

Culture as reference standard, all languages.

Data Extraction and Synthesis

Study characteristics, quality.

Main Outcome(s) and Measure(s)

Sensitivity, specificity.

Results

We included 59 studies encompassing 55,766 patients. Forty three studies (18,464 patients) fulfilled the higher quality definition (at least 50 patients, prospective data collection, and no significant biases) and 16 (35,634 patients) did not. For the higher quality immunochromatographic methods in children (10,325 patients), heterogeneity was high for sensitivity (inconsistency [I²] 88%) and specificity (I² 86%). For enzyme immunoassay in children (342 patients), the pooled sensitivity was 86% (95% CI, 79–92%) and the pooled specificity was 92% (95% CI, 88–95%). For the higher quality immunochromatographic methods in the adult population (1,216 patients), the pooled sensitivity was 91% (95% CI, 87 to 94%) and the pooled specificity was 93% (95% CI, 92 to 95%); however, heterogeneity was modest for sensitivity (I² 61%) and specificity (I² 72%). For enzyme immunoassay in the adult population (333 patients), the pooled sensitivity was 86% (95% CI, 81–91%) and the pooled specificity was 97% (95% CI, 96 to 99%); however, heterogeneity was high for sensitivity and specificity (both, I² 88%).

Conclusions

RAST immunochromatographic methods appear to be very sensitive and highly specific to diagnose group A streptococcal pharyngitis among adults but not in children. We could not identify sources of variability among higher quality studies. The present systematic review provides the best evidence for the wide range of sensitivity included in current guidelines.

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

OBJECTIVE

Group 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.

METHODS

Ninety 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.

RESULTS

Positive 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.

CONCLUSIONS

Empiric 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.

[Use of the rapid antigen technique in the diagnosis of Streptococcus pyogenes pharyngotonsillitis]

INTRODUCTION

Streptococcus pyogenes is the most frequent bacterial cause of acute tonsillopharyngitis. The validity of the rapid antigen test was analysed for its diagnosis in a Paediatric Primary Care setting. The clinical profile with better diagnostic yield was also identified. The unnecessary use of antibiotics was quantified when the rapid antigen test or only the clinical diagnosis was used. The sensitivity of the assay to penicillin, erythromycin and clindamycin was also determined.

PATIENTS AND METHODS

Cross-sectional study was conducted on children between 2 to 14 years with acute tonsillitis and/or pharyngitis seen in five Primary Care Centres, from January 2008 to May 2010. After a clinical diagnosis, two swabs were taken for pharyngotonsillar smears: the first was used for a rapid antigen test, and the second one for a culture and a study of antibiotic sensitivity, with its analysis being blind to the rapid test result. A total sample of 546 consecutive was envisaged and with consecutive sampling.

RESULTS

A total 192 patients were included. The prevalence of Streptococcus pyogenes was 38.7% (95% CI: 31.4-45.7). Odynophagia and scarlatiniform rash were most likely with positive cultures, the Streptococcus pyogenes was sensitive to penicillin in 100%, to erythromycin in 97.3% and to clindamycin in 86.3%. The specificity of the rapid antigen test was 91.5% and with a Negative Predictive Value of 91.5%. About half (49.2%) of those who would have receive antibiotics for clinical suspicion would have been treated unnecessarily, with this decreasing to at least in 29.5% when using the rapid antigen test.

CONCLUSIONS

The rapid antigen test can lead to a better use of antibiotics. Its use in Paediatric Primary Health Care could be useful when, as when the result is negative, there would be no need to confirm by a culture, in those Health Centres with difficult access to laboratory.

Diagnosis and management of acute pharyngitis in a paediatric population: a cost-effectiveness analysis

Acute pharyngitis is one of the most frequent causes of primary care physician visits; however, there is no agreement about which is the best strategy to diagnose and manage acute pharyngitis in children. The aim of the current study was to evaluate the cost-effectiveness of the recommended strategies to diagnose and manage acute pharyngitis in a paediatric population. A decision tree analysis was performed to compare the following six strategies: "treat all", "clinical scoring", "rapid test", "culture", "rapid test + culture" and "clinical scoring + rapid test". The cost data came from the Spanish National Health Service sources. Cost-effectiveness was calculated from the payer's perspective. Effectiveness was measured as the proportion of patients cured without complications from the disease and did not have any reaction to penicillin therapy; a sensitivity analysis was performed. The findings revealed that the "clinical scoring + rapid test" strategy is the most cost-effective, with a cost-effectiveness ratio of 50.72 <euro>. This strategy dominated all others except "culture", which was the most effective but also the most costly. The sensitivity analysis showed that "rapid test" became the most cost-effective strategy when the clinical scoring sensitivity was <91% and its specificity was ≤9%. In conclusion, the use of a clinical scoring system to triage the diagnoses and performing a rapid antigen test for those with a high score is the most cost-effective strategy for the diagnosis and management of acute pharyngitis in children. When the clinical scoring system has a low diagnostic accuracy, testing all patients with rapid test becomes the most cost-effective strategy.

Predicting streptococcal pharyngitis in adults in primary care: a systematic review of the diagnostic accuracy of symptoms and signs and validation of the Centor score

BACKGROUND

Stratifying patients with a sore throat into the probability of having an underlying bacterial or viral cause may be helpful in targeting antibiotic treatment. We sought to assess the diagnostic accuracy of signs and symptoms and validate a clinical prediction rule (CPR), the Centor score, for predicting group A β-haemolytic streptococcal (GABHS) pharyngitis in adults (> 14 years of age) presenting with sore throat symptoms.

METHODS

A systematic literature search was performed up to July 2010. Studies that assessed the diagnostic accuracy of signs and symptoms and/or validated the Centor score were included. For the analysis of the diagnostic accuracy of signs and symptoms and the Centor score, studies were combined using a bivariate random effects model, while for the calibration analysis of the Centor score, a random effects model was used.

RESULTS

A total of 21 studies incorporating 4,839 patients were included in the meta-analysis on diagnostic accuracy of signs and symptoms. The results were heterogeneous and suggest that individual signs and symptoms generate only small shifts in post-test probability (range positive likelihood ratio (+LR) 1.45-2.33, -LR 0.54-0.72). As a decision rule for considering antibiotic prescribing (score ≥ 3), the Centor score has reasonable specificity (0.82, 95% CI 0.72 to 0.88) and a post-test probability of 12% to 40% based on a prior prevalence of 5% to 20%. Pooled calibration shows no significant difference between the numbers of patients predicted and observed to have GABHS pharyngitis across strata of Centor score (0-1 risk ratio (RR) 0.72, 95% CI 0.49 to 1.06; 2-3 RR 0.93, 95% CI 0.73 to 1.17; 4 RR 1.14, 95% CI 0.95 to 1.37).

CONCLUSIONS

Individual signs and symptoms are not powerful enough to discriminate GABHS pharyngitis from other types of sore throat. The Centor score is a well calibrated CPR for estimating the probability of GABHS pharyngitis. The Centor score can enhance appropriate prescribing of antibiotics, but should be used with caution in low prevalence settings of GABHS pharyngitis such as primary care.

[Early diagnosis of streptococcal pharyngitis in paediatric practice: Validity of a rapid antigen detection test]

OBJECTIVE

To determine the validity of the rapid antigen test for the diagnoses of acute pharyngitis caused by group A beta-haemolytic Streptococcus (GABHS) compared with culture.

DESIGN

Observational study of a consecutive sample of paediatric patients.

SETTING

Two primary care centres (PCC) from the metropolitan area of Barcelona.

PARTICIPANTS

Children aged 1-14 years with sore throat of no more than 5 days duration were chosen at PCC.

PRINCIPAL MEASUREMENTS

Oropharyngeal samples were collected from tonsillar bed and posterior pharynx. A rapid diagnostic test was performed, as well as a throat culture.

RESULTS

A total of 211 patients were studied. The overall prevalence of pharyngitis due to Streptococcus was 34.1%. Compared with the throat culture, the sensitivity of the rapid test was 90.3% (95% CI: 81.0-96.0), the specificity was 78.4% (95% CI: 70.6-84.9). The percentage of false negatives was 9.7% and the false positives was 21.6%. Spectrum bias was present, inasmuch as the rapid test sensitivity increased with Centor scores.

CONCLUSIONS

The diagnostic value of a rapid antigen test for the diagnosis of streptococcal pharyngitis in paediatric patients at PCC is high. However, the percentage of false positives and negatives is too high, and also the sensitivity is too low in patients with fewer symptoms to support the use of rapid antigenic test without culture confirmation and bacterial sensitivity test.

[Evaluation of rapid methods for detecting Streptococcus pyogenes. Systematic review and meta-analysis]

INTRODUCTION

Streptococcal pharyngitis is one of the most frequent reasons for consultations in primary and paediatric care. An inadequate treatment could cause adverse effects and bacterial resistance. The rapid antigen tests are an important advance, enabling the diagnosis of infection by Streptococcus pyogenes to be diagnosed in a few minutes. The aim of this review is to assess the rapid antigen-detection test in the diagnosis of S. pyogenes from throat samples.

MATERIAL AND METHODS

Systematic review and meta-analysis (2000-09). Source database: MedLine, Embase, Cochrane Library, Cinahl, CRD, ECRI, Hayes and HTA's agencies. The quality of included studies was measured according to Quadas's criteria. The diagnostic validity indices have been calculated. A meta-analysis was performed in order to synthesize the results of the different evaluated studies.

RESULTS

Twenty four studies were included. The quality was moderate. The sensitivity ranged between 65.6% and 96.4%; specificity from 68.7%-99.3%; the positive predictive value was between 59.4%-97.4%; and the negative predictive value from 87.8%-98%. The meta-analysis determined an overall sensitivity of 0.85 [95% CI, 0.84-0.87], specificity was 0.96 [95% CI, 0.96-0.97], likelihood ratio (+) 22.21 [95% CI, 15.12-32.63], and likelihood ratio (-) 0.15 [95% CI, 0.13-0.18]. The rapid antigen-detection test demonstrated a good diagnostic performance.

CONCLUSIONS

Rapid tests offer good accuracy for use as diagnostic method, however, these devices have to be complemented with the microbiological culture, because there are false positive and negative results.

Repetition of the rapid antigen test in initially negative supposed streptococcal pharyngitis is not necessary in adults

AIMS

To determine whether the repetition of the rapid antigen detection test (RADT) in patients, with a high suspicion of presenting pharyngitis by group A beta-haemolytic streptococci (GABHS), with a previously negative test improves the validity of the test.

METHODS

Two hundred and twenty-two patients aged 14 years or more with acute pharyngitis and two or more Centor criteria--tonsillar exudates, fever, tenderness in the lymph glands and/or absence of cough--were consecutively recruited. In all patients, a pharyngotonsillar sample was obtained with two swabs, one for the RADT (OSOM Strep A Genzyme test, Genzyme Diagnostics, Cambridge, MA, USA) and the other was sent to the Department of Microbiology for culture. In patients with a negative RADT, the determination was repeated. The sensitivity, specificity and predictive values were determined.

RESULTS

Cultures were positive for GABHS in 55 patients (24.8%). Three false-negatives and 14 false-positives were observed by comparing the rapid test with throat culture, achieving a sensitivity of 94.5% and a specificity of 91.6%. Positive and negative predictive values were 78.8% and 98.1% respectively. Taking the second determination in the negative cases into account, the results were 96.4%, 91.6%, 79.1% and 98.7% respectively.

CONCLUSIONS

The negative predictive value achieved with the RADT determination was very high. Repetition of the test only slightly improved this percentage, making repetition of this test unnecessary.