The impact of a rapid screen for streptococcal pharyngitis on clinical decision making in the emergency department

Efficacy and safety of rapid tests to guide antibiotic prescriptions for sore throat

BACKGROUND

Sore throat is a common condition caused by viruses or bacteria, and is a leading cause of antibiotic prescription in primary care. The most common bacterial species is group A streptococcus ('strep throat'). Between 50% to 70% of pharyngitis cases are treated with antibiotics, despite the majority of cases being viral in origin. One strategy to reduce antibiotics is to use rapid tests for group A streptococcus to guide antibiotic prescriptions. Rapid tests can be used alone or in combination with a clinical scoring system.

OBJECTIVES

To assess the efficacy and safety of strategies based on rapid tests to guide antibiotic prescriptions for sore throat in primary care settings.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, Web of Science, and LILACS, as well as the trial registries ClinicalTrials.gov and the WHO ICTRP on 5 June 2019.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing rapid tests with management based on clinical grounds to guide the prescription of antibiotics for people with a sore throat in ambulatory care settings. We included trials that randomised individuals, as well as cluster-RCTs in which individual practitioners (or practices) or emergency departments were randomised.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on the primary outcomes (number of participants provided with an antibiotic prescription; number of participants with an antibiotic dispensed) and secondary outcomes (duration of sore throat symptoms; duration of other symptoms; quality of life measures; number of participants with a complication attributed to the index infection; number of participants in need of re-consultation by the end of follow-up; number of participants in need of hospital admission by the end of follow-up; number of satisfied participants; number of participants with an adverse event attributed to the rapid test). We assessed the risk of bias of all included trials and used GRADE to assess the certainty of the evidence. We performed meta-analyses and sensitivity analyses when feasible.

MAIN RESULTS

We included five trials (2891 children and adult participants in total; 2545 participants after adjusting for clustering). Management in the intervention group was as follows: in three trials rapid tests were used in combination with a clinical scoring system; in one trial, some physicians were asked to use rapid tests alone, while others were asked to use rapid tests in combination with a clinical scoring system; in one trial, rapid tests were used alone. Based on data from five trials (2545 participants), a large reduction in prescribed antibiotics was found in the rapid test group (481/1197) versus management based on clinical grounds (865/1348), for a summary risk difference (RD) of -25%, 95% confidence interval (CI) -31% to -18%; I² = 62%; moderate-certainty evidence. Estimates of effect on antibiotic prescription rates were stable in various sensitivity analyses. Based on data from two trials (900 people) originating from the same overarching study, the evidence suggests that rapid tests may not reduce dispensed antibiotic treatments: rapid test group (156/445) versus management based on clinical grounds (197/455); summary RD -7%, 95% CI -17% to 2%; I² = 53%; low-certainty evidence. Four trials (2075 participants) reported data on the number of participants with a complication attributed to the index infection; the summary odds ratio (OR) was 0.85, 95% CI 0.03 to 26.65; P = 0.93; I² = 62%; very low-certainty evidence, which means that people in the rapid testing group were less likely to develop complications of the index infection, but the evidence is very uncertain. Two trials (1161 participants) reported on the number of participants in need of re-consultation by the end of follow-up; the summary OR was 1.12, 95% CI 0.57 to 2.21; P = 0.74; I² = 59%; low-certainty evidence, which means that participants in the rapid testing group were more likely to be in need of re-consultation by the end of the study follow-up, but the evidence is uncertain. Lack of data impeded assessment of other secondary outcomes (including safety outcomes) and of sources of heterogeneity.  AUTHORS' CONCLUSIONS: Rapid testing to guide antibiotic treatment for sore throat in primary care probably reduces antibiotic prescription rates by 25% (absolute risk difference), but may have little or no impact on antibiotic dispensing. More studies are needed to assess the efficacy and safety of rapid test-guided antibiotic prescribing, notably to evaluate patient-centred outcomes and variability across subgroups (e.g. adults versus children).

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.

Practice variation in the management of pharyngitis: the importance of variability in patients' clinical characteristics and in physicians' responses to them

The objective of this study was to assess whether geographic differences in antibiotic-prescribing rates for patients with pharyngitis could be explained by intersite differences in patients' clinical characteristics and in how physicians responded to these clinical cues when making decisions. As part of the initial phase of a prospective controlled trial to improve physicians' diagnostic ability, the authors enrolled cohorts of consecutive patients seen at staff-model--HMO student health services in Pennsylvania and Nebraska. Physicians' decisions whether to prescribe antibiotics for 310 consecutive patients presenting with pharyngitis to the former and 214 such patients presenting to the latter at the time of the initial visit were examined. There was a large discrepancy between the antibiotic-prescribing rates at the student health services in Pennsylvania, 106/310, 32.4%, and Nebraska, 156/214, 72.9%. The clinical variables significantly independently associated with treatment at both sites in a logistic regression model were fever, adjusted odds ratio = 2.1 (95% CI = 1.1, 3.8); exudates, 5.4 (2.8, 10); palatine petechiae, 6.5 (1.5, 28); rhinorrhea, 0.46, (0.25, 0.85); and high risk of complications, 3.8 (1.04, 14). There was a significant interaction between site and anterior cervical adenopathy, 5.5 (1.6, 19); and a borderline interaction between site and rhinorrhea, 2.4 (0.89, 6.7). Site was not a significant independent predictor of treatment, 1.8 (0.45, 6.6.). Practice variation was related to geographic differences in patients' clinical characteristics and in how physicians responded to these factors when prescribing antibiotics. How physicians weight patients' clinical characteristics when making decisions may be an important element of their "practice styles."

Proposals for health care reform: how do we evaluate them?

The Society for Academic Emergency Medicine suggests a systematic approach to evaluating proposals for reform of the medical care system. Described are the three components of the problem--access, cost, and quality. Then, goals are proposed for health care reform. With this background, we describe the major questions that reform proposals must address and the potential impact of reform on emergency medicine. Emergency physicians must actively support health reform legislation that is in the over-all best interest or our patients and our specialty, and work with the new federal administration to evaluate proposed changes.

Using treatment-tradeoff preferences to select diagnostic strategies: linking the ROC curve to threshold analysis

Selection of optimal diagnostic strategies depends on the accuracy of diagnostic tests, the prevalence of disease, and the relative benefits and harms resulting from test/treatment choices. One can characterize diagnostic strategies according to their net benefit-to-harm ratios. Within the framework of expected-utility theory, the benefit-to-harm ratio is equivalent to the marginal tradeoff between erroneous and correct treatment choices. Consequently, a physician can identify his or her preferred strategy by asking the question: "How many additional treatment errors am I willing to make in order to treat one additional person correctly?" Family physicians were asked to indicate their lowest and highest acceptable tradeoff ratios in a survey about streptococcal pharyngitis. All 53 respondents indicated uncertainty about their preferred treatment-tradeoff ratios. For 58% of respondents, the midpoints of the acceptable range of tradeoff ratios corresponded to generally accepted diagnostic strategies: 1) test all or 2) treat if classic, test all others. In contrast, previously published patient utilities yield a treatment-tradeoff ratio that corresponds to the strategy of treating all cases. The analysis illustrates the linkage between the optimal operating point on a receiver operating characteristic (ROC) curve and the selection of a preferred diagnostic strategy based on treatment thresholds derived from benefit-to-harm ratios. The survey results indicate that physicians can respond directly to questions assessing their preferences for such treatment thresholds. Differences between patients and physicians have significant impacts on choices of test and treatment strategies.