Clinical performance evaluation of total protein measurement by digital refractometry and characterization of non-protein solute interferences

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• 作者：Joshua J.H. Hunsaker^a ; Sara P. Wyness^a ; Taylor M. Snow^a ; Jonathan R. Genzen^a ; ^b ; ^{jonathan.genzen@path.utah.edu}
• 关键词：ALB ; albumin ; AMR ; analytical measurement range ; ARUP ; Associated Regional & University Pathologists ; BILI ; bilirubin ; CAP ; College of American Pathologists ; CLSI ; Clinical & Laboratory Standards Institute ; CSF ; cerebrospinal fluid ; CV ; coefficient of variation ; ddH2O ; demineralized distilled water ; GLU ; glucose ; Hb ; hemoglobin ; IRB ; Institutional Review Board ; LOQ ; limit of quantitation ; NaCl ; sodium chloride ; PT ; proficiency testing ; QC ; quality control ; RI ; reference interval ; SD ; standard de
• 刊名：Practical Laboratory Medicine
• 出版年：2016
• 出版时间：1 December 2016
• 年：2016
• 卷：6
• 期：Complete
• 页码：14-24
• 全文大小：1154 K
• 卷排序：6

文摘

Refractometric methods to measure total protein (TP) in serum and plasma specimens have been replaced by automated biuret methods in virtually all routine clinical testing. A subset of laboratories, however, still report using refractometry to measure TP in conjunction with serum protein electrophoresis. The objective of this study was therefore to conduct a modern performance evaluation of a digital refractometer for TP measurement.Design and methodsPerformance evaluation of a MISCO Palm Abbe™ digital refractometer was conducted through device familiarization, carryover, precision, accuracy, linearity, analytical sensitivity, analytical specificity, and reference interval verification. Comparison assays included a manual refractometer and an automated biuret assay.ResultsCarryover risk was eliminated using a demineralized distilled water (ddH2O) wash step. Precision studies demonstrated overall imprecision of 2.2% CV (low TP pool) and 0.5% CV (high TP pool). Accuracy studies demonstrated correlation to both manual refractometry and the biuret method. An overall positive bias (+5.0%) was observed versus the biuret method. On average, outlier specimens had an increased triglyceride concentration. Linearity was verified using mixed dilutions of: a) low and high concentration patient pools, or b) albumin-spiked ddH2O and high concentration patient pool. Decreased recovery was observed using ddH2O dilutions at low TP concentrations. Significant interference was detected at high concentrations of glucose (>267 mg/dL) and triglycerides (>580 mg/dL). Current laboratory reference intervals for TP were verified.ConclusionsPerformance characteristics of this digital refractometer were validated in a clinical laboratory setting. Biuret method remains the preferred assay for TP measurement in routine clinical analyses.