Mochon, A. Brian

Abstract This publication represents the first part of an update to the clinical practice guideline on the diagnosis and management of group A streptococcal (GAS) pharyngitis, developed by the Infectious Diseases Society of America (IDSA). Diagnosis of GAS pharyngitis by clinician judgment alone is unreliable, and universal testing incurs cost and inconvenience for individuals at low risk of having GAS infection. Clinical scoring systems have been used to quantify the probability of a positive GAS throat culture based on standardized criteria such as the presence of fever, tonsillar enlargement or exudate, tender and enlarged anterior cervical lymph nodes, and the absence of cough. The goal of this manuscript is to review the evidence and provide a recommendation as to whether a scoring system should be used to decide which patients should have a GAS diagnostic test (ie, rapid antigen test [RADT], molecular method, and/or throat culture) performed. We performed a systematic review of randomized and nonrandomized studies that compared the use of a clinical scoring system to clinician judgment alone in predicting the result of a throat culture. Evidence from studies in children and adults suggests the diagnostic accuracy is comparable or slightly higher using a scoring system compared to clinician judgment alone. Although the studies are limited due to small size, lack of uniformity in outcome measures, and incomplete data, the consensus of the panel is that the balance of benefits and harms favors incorporation of a clinical scoring system as part of the evaluation of patients with sore throat and suspected GAS pharyngitis.

Abstract This publication represents the first part of an update to the clinical practice guideline on the diagnosis and management of group A streptococcal (Streptococcus pyogenes or GAS) pharyngitis, developed by the Infectious Diseases Society of America (IDSA). Diagnosis of GAS pharyngitis by clinician judgment alone is unreliable, and unselective testing incurs cost and inconvenience for individuals at low risk of having GAS infection. Clinical scoring systems have been used to quantify the probability of a positive GAS throat culture based on standardized criteria such as the presence of fever; tonsillar enlargement or exudate; tender and enlarged anterior cervical lymph nodes; and the absence of cough. The goal of this article is to determine whether a scoring system should be used to decide which patients should have a diagnostic test performed by rapid antigen detection test, molecular methods, and/or throat culture. We performed a systematic review of randomized and nonrandomized studies that compared the use of a clinical scoring system to clinician judgment alone in predicting the outcome of a throat culture. Evidence from studies in children and adults suggests the diagnostic accuracy of a clinical scoring system is comparable to or slightly higher than clinician judgment alone. However, the studies are limited due to small size, lack of uniformity in outcome measures, and incomplete data. The consensus of the panel is that the balance of benefits and harms favors use of a clinical scoring system as part of the evaluation of patients with sore throat. The principal utility of using a scoring system is to identify patients with low probability of GAS pharyngitis and to reduce unnecessary testing.

SUMMARY Bloodstream infections (BSIs) are a significant cause of mortality and morbidity. Rapid identification of pathogens and detection of a few resistance markers from positive blood cultures are now possible through the increased availability of commercial rapid diagnostic tests, including nucleic acid amplification tests and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This document describes the clinical utility of rapid diagnostics performed on positive blood cultures and provides evidence-based laboratory medicine guidelines for using rapid tests to diagnose BSIs in hospitalized adult and pediatric patients. This guideline was developed for use by medical (a.k.a. clinical) microbiologists, medical laboratory professionals, infectious disease clinicians, pharmacists, hospital administrators, healthcare providers, and other stakeholders associated with BSIs. A panel of experts, including medical microbiologists and experts in systematic literature review, was assembled to formulate the Population–Intervention–Comparison–Outcome (PICO) question, review the literature, and provide recommendations for using rapid tests to diagnose BSI and improve patient outcomes. A comprehensive literature search of four electronic bibliographic databases (MEDLINE, Embase, CINAHL, and Cochrane) was conducted to identify studies with measurable outcomes. The panel followed a systematic process, which included a standardized methodology for rating the certainty of the evidence and strength of recommendations using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. The panel evaluated the literature to answer the question: Does using rapid diagnostic tests improve clinical outcomes in adult and pediatric patients hospitalized with a BSI? Peer-reviewed literature was available to address three outcomes, including time to targeted therapy, mortality, and length of hospital stay. In general, the quality of the evidence was low to moderate due to the paucity of controlled, randomized clinical trial studies. However, eight recommendations were made based on evidence derived from the systematic review of the published literature. To answer the PICO question, the expert committee recommended using rapid diagnostic tests combined with active communication to decrease the time to targeted therapy and length of stay (strong recommendation). While the strength of the evidence for the impact on mortality is low, the panel supports using rapid tests to impact these outcomes. A summary of the recommendations is listed in the Executive Summary, which includes a detailed description of the background, methods, evidence summary, and rationale that supports each recommendation in the full text.

ABSTRACT We describe results from a multicenter study evaluating the Accelerate Pheno system, a first of its kind diagnostic system that rapidly identifies common bloodstream pathogens from positive blood cultures within 90 min and determines bacterial phenotypic antimicrobial susceptibility testing (AST) results within ∼7 h. A combination of fresh clinical and seeded blood cultures were tested, and results from the Accelerate Pheno system were compared to Vitek 2 results for identification (ID) and broth microdilution or disk diffusion for AST. The Accelerate Pheno system accurately identified 14 common bacterial pathogens and two Candida spp. with sensitivities ranging from 94.6 to 100%. Of fresh positive blood cultures, 89% received a monomicrobial call with a positive predictive value of 97.3%. Six common Gram-positive cocci were evaluated for ID. Five were tested against eight antibiotics, two resistance phenotypes (methicillin-resistant Staphylococcus aureus and Staphylococcus spp. [MRSA/MRS]), and inducible clindamycin resistance (MLSb). From the 4,142 AST results, the overall essential agreement (EA) and categorical agreement (CA) were 97.6% and 97.9%, respectively. Overall very major error (VME), major error (ME), and minor error (mE) rates were 1.0%, 0.7%, and 1.3%, respectively. Eight species of Gram-negative rods were evaluated against 15 antibiotics. From the 6,331 AST results, overall EA and CA were 95.4% and 94.3%, respectively. Overall VME, ME, and mE rates were 0.5%, 0.9%, and 4.8%, respectively. The Accelerate Pheno system has the unique ability to identify and provide phenotypic MIC and categorical AST results in a few hours directly from positive blood culture bottles and support accurate antimicrobial adjustment.