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This study determined the performance characteristics of a quantitative glucose-6-phosphate dehydrogenase (G6PD) assay with automated lysis and evaluated the robustness of the operational workflow following implementation in a hospital laboratory. The G6PD activity was measured in whole blood using an enzymatic quantitative test on a Roche cobas c501 analyzer with onboard lysis configuration and normalized to hemoglobin (Hb). The performance characteristics of the method and stability of G6PD in whole blood collected in EDTA-containing tubes were evaluated, and the reference interval was established on a population of healthy individuals (n = 279). The robustness of this automated workflow for sample lysis was evaluated during validation and after implementation for routine clinical use for 18 months and in 2,181 patients. The G6PD assay was linear from 0.7 to 16.5 U/g Hb. Inter- and intra-assay precision using control and patient samples was below 12%. The G6PD results correlated well with a reference laboratory method (r = 0.96, y = 0.9615x - 1.222). The reference interval in our population was 9.8 to 15.5 U/g Hb. There were no interferences by lipemia and icteria, although grossly hemolyzed specimens may be affected. The testing workflow requires analyzing samples within minutes from mixing and loading into the instrument to avoid sample sedimentation. Measures to repeat samples with Hb 8.0 g/dL or less identified sedimented samples. In our patient population, 10.6% and 5.8% of the total males and females tested were G6PD deficient, respectively. The G6PD assay with automated lysis is acceptable for patient testing. Several measures ensured the robustness of this workflow in a hospital laboratory.

ContextThe normal cortisol response 30 or 60 minutes after cosyntropin (ACTH[1–24]) is considered to be ≥18 μg/dL (500 nmol/L). This threshold is based on older serum cortisol assays. Specific monoclonal antibody immunoassays or LC-MS/MS may have lower thresholds for a normal response. ObjectiveTo calculate serum cortisol cutoff values for adrenocorticotropic hormone (ACTH) stimulation testing with newer specific cortisol assays. MethodsRetrospective analysis of ACTH stimulation tests performed in ambulatory and hospitalized patients suspected of adrenal insufficiency (AI). Serum samples were assayed for cortisol in parallel using Elecsys I and Elecsys II immunoassays, and when volume was available, by Access immunoassay and LC-MS/MS. ResultsA total of 110 patients were evaluated. Using 18 μg/dL as the cortisol cutoff after ACTH stimulation, 14.5%, 29%, 22.4%, and 32% of patients had a biochemical diagnosis of AI using the Elecsys I, Elecsys II, Access, and LC-MS/MS assays, respectively. Deming regressions of serum cortisol were used to calculate new cortisol cutoffs based on the Elecsys I cutoff of 18 μg/dL. For 30-minute values, new cutoffs were 14.6 μg/dL for Elecsys II, 14.8 μg/dL for Access, and 14.5 μg/dL for LC-MS/MS. Baseline cortisol <2 μg/dL was predictive of subnormal stimulated cortisol values. ConclusionTo reduce false positive ACTH stimulation testing, we recommend a new serum cortisol cutoff of 14 to 15 μg/dL depending on the assay used (instead of the historical value of 18 μg/dL with older polyclonal antibody assays). Clinicians should be aware of the new cutoffs for the assays available to them when evaluating patients for AI.

[...]plasmapheresis was used to reduce the serum triglyceride concentrations on day 3 posthospital presentation, but triglycerides persisted at >4425 mg/dL (Table 1). [...]we explored whether increased triglycerides and discrepantly low L could be used to investigate pseudohypertriglyceridemia in our laboratory. Patients with GKD rarely have such high triglyceride concentrations. [...]the method used to derive these cutoffs lacked validation, and these institutional observations may not be adequate for universal use. Triglyceride concentrations in this patient were much higher than reported for GKD (usually <1000 mg/dL). [...]triglyceride concentrations decreased during her hospital stay without further intervention (Table 1), suggesting an exogenous glycerol source.

(1) Biomarkers are vital for drug development, with potential safety (e.g., early identification of drug toxicity) and efficacy (e.g., response to therapy, end-point measures) benefits. [...]stakeholders are committed to developing pathways for effective biomarker qualification. Recently, the Center for Drug Evaluation and Research put forth biomarker qualification guidelines aiming at expediting and clarifying this process. Since the beginning of the Biomarker Qualification Program in 2007, only 6 biomarkers have been qualified though the program (1). Author Contributions: All authors confirmed they have contributed to the intellectual content ofthispaper and have met the following3 requirements: (a) significant contribution to the conception and design, acquisition of data, or analysis and interpretation ofdata; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Abstract Background Procalcitonin (PCT), a peptide precursor of the hormone calcitonin, is a biomarker whose serum concentrations are elevated in response to systemic inflammation caused by bacterial infection and sepsis. Clinical adoption of PCT in the United States has only recently gained traction with an increasing number of Food and Drug Administration–approved assays and expanded indications for use. There is interest in the use of PCT as an outcomes predictor as well as an antibiotic stewardship tool. However, PCT has limitations in specificity, and conclusions surrounding its utility have been mixed. Further, there is a lack of consensus regarding appropriate timing of measurements and interpretation of results. There is also a lack of method harmonization for PCT assays, and questions remain regarding whether the same clinical decision points may be used across different methods. Content This guidance document aims to address key questions related to the use of PCT to manage adult, pediatric, and neonatal patients with suspected sepsis and/or bacterial infections, particularly respiratory infections. The document explores the evidence for PCT utility for antimicrobial therapy decisions and outcomes prediction. Additionally, the document discusses analytical and preanalytical considerations for PCT analysis and confounding factors that may affect the interpretation of PCT results. Summary While PCT has been studied widely in various clinical settings, there is considerable variability in study designs and study populations. Evidence to support the use of PCT to guide antibiotic cessation is compelling in the critically ill and in some lower respiratory tract infections but is lacking in other clinical scenarios, and evidence is also limited in the pediatric and neonatal populations. Interpretation of PCT results requires guidance from multidisciplinary care teams of clinicians, pharmacists, and clinical laboratorians.