Wolk, Donna M.

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 Many patients in the emergency department present with signs and symptoms that arouse concern for sepsis; however, other explanations are also possible. There are currently no rapid tests used in clinical practice that reliably distinguish the presence of a bacterial or viral infection vs. a non-infectious etiology and can predict a patient’s likelihood to decompensate. The diagnostic and prognostic uncertainty in “gray zone” patients complicates the decision to begin therapy as clinicians need to balance the risk of withholding therapy vs. the risk of the therapy itself (e.g., overtreatment with antibiotics and hospitalization, which is costly, potentially harmful, and contributes to antibiotic resistance). The TriVerity™ Test uses isothermal amplification and machine-learning algorithms to quantify and interpret mRNA expression levels to determine both likelihood of bacterial infection, viral infection, or no infection, and whether the patient will likely require one or more critical interventions within 7 days. The three scores each fall into one of five interpretation bands ranging from Very high to Very low. Testing takes approximately 30 minutes using the proprietary Myrna™ Instrument with an operator hands-on-time of under one minute. We enrolled 1,222 patients from 22 emergency departments (ED) to validate the performance of the TriVerity Test. Patients were treated as per local standard of care and were followed for 28 days. Bacterial and viral TriVerity results were validated against clinically adjudicated infection status; the illness severity TriVerity result was validated against the need for at least one critical interventions within 7 days. The bacterial TriVerity result had high AUROC for the diagnosis of bacterial infection (0.83; 80% CI 0.81–0.85) and divided bacterial infection likelihood scores into five interpretation bands with increasing likelihood ratios of infection ranging from Very low (LR- 0.08, 80% CI 0.06–0.11) to Very high (LR + 8.04, 80% CI 5.72–11.78). The AUROC for the bacterial TriVerity result was significantly higher compared to AUROCs for C-reactive protein, procalcitonin or white blood cell count. Similarly, the viral TriVerity score showed high AUROC for the diagnosis of viral infection (0.91; 80% CI 0.90–0.93) and likelihood ratios from Very low (LR- 0.09, 80% CI 0.05–0.14) to Very high (LR + 40.93; 80% CI 29.11–79.23). The TriVerity Illness Severity score showed a high AUROC for the prediction of illness severity (0.77; 80% CI 0.77–0.81) with scores divided into five interpretation bands with increasing likelihood ratios ranging from Very low (LR- 0.22; 80% CI 0.14–0.33) to Very high (LR + 11.33; 80% CI 7.31–17.00). TriVerity illness severity results allowed marked re-classification of the risk for “ICU-level care” as compared to clinical assessment (qSOFA scores) alone. In conclusion, TriVerity provides rapid, highly accurate and actionable results for the diagnosis and prognosis of patients with suspected acute infection and/or sepsis, supporting a major unmet medical need. TriVerity may improve personalized management of patients with suspected acute infections and suspected sepsis for improved overall healthcare outcomes.

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.

SUMMARY Within the past decade, clinical microbiology laboratories experienced revolutionary changes in the way in which microorganisms are identified, moving away from slow, traditional microbial identification algorithms toward rapid molecular methods and mass spectrometry (MS). Historically, MS was clinically utilized as a high-complexity method adapted for protein-centered analysis of samples in chemistry and hematology laboratories. Today, matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) MS is adapted for use in microbiology laboratories, where it serves as a paradigm-shifting, rapid, and robust method for accurate microbial identification. Multiple instrument platforms, marketed by well-established manufacturers, are beginning to displace automated phenotypic identification instruments and in some cases genetic sequence-based identification practices. This review summarizes the current position of MALDI-TOF MS in clinical research and in diagnostic clinical microbiology laboratories and serves as a primer to examine the “nuts and bolts” of MALDI-TOF MS, highlighting research associated with sample preparation, spectral analysis, and accuracy. Currently available MALDI-TOF MS hardware and software platforms that support the use of MALDI-TOF with direct and precultured specimens and integration of the technology into the laboratory workflow are also discussed. Finally, this review closes with a prospective view of the future of MALDI-TOF MS in the clinical microbiology laboratory to accelerate diagnosis and microbial identification to improve patient care.

ABSTRACT The prevalence of microsporidiosis is likely underestimated due to the labor-intensive, insensitive, and nonspecific clinical laboratory methods used for the diagnosis of this disease. A real-time PCR assay was designed to assess DNA extraction methods and to detect three Encephalitozoon species in feces. Modifications of the MagNA Pure LC DNA isolation kit protocol (Roche Applied Sciences, Indianapolis, Ind.) were compared by using the automated MagNA Pure LC instrument (Roche) and fecal specimens spiked with Encephalitozoon intestinalis spores. Extracted DNA was amplified by the LightCycler (Roche) PCR assay. Assay sensitivity, reproducibility, and efficiency were assessed by comparing threshold crossover values achieved with different extraction and storage conditions (fresh, refrigerated, frozen, and preserved specimens). Optimal extraction conditions were achieved by using a commercial buffer, tissue lysis buffer (Roche), as the specimen diluent. LightCycler PCR results were compared to those obtained from routine stool microscopy with trichrome blue stain. The lower limit of detection for the LightCycler PCR assay varied by storage conditions from 10 2 to 10 4 spores/ml of feces, a value which represented a significant improvement over that achieved by staining (≥1.0 × 10 6 spores/ml). Melting temperature analysis of the amplicons allowed for the differentiation of three Encephalitozoon species ( E . intestinalis , E . cuniculi , and E . hellem ). The assay is readily adaptable to the clinical laboratory and represents the first real-time PCR assay designed to detect Encephalitozoon species.