[Is streptococcal pharyngitis diagnosis possible?]

[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.

Comparison of Centor and McIsaac scores in primary care: a meta-analysis over multiple thresholds

Background

Centor and McIsaac scores are both used to diagnose group A beta-haemolytic streptococcus (GABHS) infection, but have not been compared through meta-analysis.

Aim

To compare the performance of Centor and McIsaac scores at diagnosing patients with GABHS presenting to primary care with pharyngitis.

Design and setting

A meta-analysis of diagnostic test accuracy studies conducted in primary care was performed using a novel model that incorporates data at multiple thresholds.

Method

MEDLINE, EMBASE, and PsycINFO were searched for studies published between January 1980 and February 2019. Included studies were: cross-sectional; recruited patients with sore throats from primary care; used the Centor or McIsaac score; had GABHS infection as the target diagnosis; used throat swab culture as the reference standard; and reported 2 × 2 tables across multiple thresholds. Selection and data extraction were conducted by two independent reviewers. QUADAS-2 was used to assess study quality. Summary receiver operating characteristic (SROC) curves were synthesised. Calibration curves were used to assess the transferability of results into practice.

Results

Ten studies using the Centor score and eight using the McIsaac score were included. The prevalence of GABHS ranged between 4% and 44%. The areas under the SROC curves for McIsaac and Centor scores were 0.7052 and 0.6888, respectively. The P-value for the difference (0.0164) was 0.419, suggesting the SROC curves for the tests are equivalent. Both scores demonstrated poor calibration.

Conclusion

Both Centor and McIsaac scores provide only fair discrimination of those with and without GABHS, and appear broadly equivalent in performance. The poor calibration for a positive test result suggests other point-of-care tests are required to rule in GABHS; however, with both Centor and McIsaac scores, a score of ≤0 may be sufficient to rule out infection.

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.

The patient with sore throat

Sore throat is a common medical complaint seen by the emergency practitioner, internist, pediatrician, and otolaryngologist. The differential for sore throat is vast. However, with a directed history this can often be narrowed down to 2 to 3 possible diagnoses. By paying particular attention to the associated symptoms and duration of symptoms, common self-limited etiologies like viral pharyngitis and nonstreptococcal tonsillitis can be distinguished from those that require more investigation, such as supraglottitis and tonsillar cancer. A sore throat is most commonly caused by an infectious, inflammatory, or neoplastic etiologic factor.

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

OBJECTIVE

To determine the validity of the rapid antigen test (RAT) OSOM StrepA Genzyme for the diagnosis of acute pharyngitis caused by group A beta-haemolytic strep (GABHS).

DESIGN

Diagnostic techniques survey.

SETTING

Urban primary care centre, Spain.

PARTICIPANTS

All patients over 14 years old seen in 6 surgeries with sore throat and 2 or more Centor criteria: pharyngotonsillar exudate, tender laterocervical nodes, absence of coughing, and/or history or presence of fever.

PRINCIPAL MEASUREMENTS

Pharyngeal swabs were taken from all the patients, one for RAT and another to send for culture in the microbiology department.

RESULTS

A total of 182 patients were evaluable, with a mean age of 30.6 (12.1) years of which 116 were women (63.7%); 63 patients had 2 Centor criteria; 83 had 3 and 36, the 4 criteria. The culture was positive in 102 patients (56%), with GABHS showing infection in forty (22%; 95% confidence interval [CI], 21.2-22.8). Group C Streptococcus was isolated in 26 patients (14.3%). GABHS was higher among patients with four Centor criteria (38.9% vs 25.3% observed among those with 3 criteria and 7.9% with 2 criteria; P<.001). Sensitivity of RAT was 95%, with a specificity of 93%, a positive predictive value of 79.2% and a negative predictive value of 98.5%.

CONCLUSIONS

These results show the usefulness of RAT for diagnosing streptococcal pharyngitis. Its use should be spread to all primary care practices.