Refrigeration of blood samples prior to separation is essential for the accurate determination of plasma or serum zinc concentrations

Tamura, Tsunenobu; Johnston, Kelley E.; Freeberg, L. E.; Perkins, Laura; Goldenberg, Robert L.

doi:10.1007/bf02917226

Cited by 42 publications

(29 citation statements)

References 22 publications

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“…It is also acknowledged that hemolysis could lead to spurious increases in PZC and SZC (6, 15–19), although there is little information as to what level of hemolysis creates a concern. Most studies that reported PZC or SZC have limited or no detailed description of how hemolysis was categorized.…”

Section: Introductionmentioning

confidence: 99%

Identification of a Hemolysis Threshold That Increases Plasma and Serum Zinc Concentration

Killilea¹,

Rohner²,

Ghosh

et al. 2017

The Journal of Nutrition

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Background: Plasma or serum zinc concentration (PZC or SZC) is the primary measure of zinc status, but accurate sampling requires controlling for hemolysis to prevent leakage of zinc from erythrocytes. It is not established how much hemolysis can occur without changing PZC/SZC concentrations.Objective: This study determines a guideline for the level of hemolysis that can significantly elevate PZC/SZC.Methods: The effect of hemolysis on PZC/SZC was estimated by using standard hematologic variables and mineral content. The calculated hemolysis threshold was then compared with results from an in vitro study and a population survey. Hemolysis was assessed by hemoglobin and iron concentrations, direct spectrophotometry, and visual assessment of the plasma or serum. Zinc and iron concentrations were determined by inductively coupled plasma spectrometry.Results: A 5% increase in PZC/SZC was calculated to result from the lysis of 1.15% of the erythrocytes in whole blood, corresponding to ∼1 g hemoglobin/L added into the plasma or serum. Similarly, the addition of simulated hemolysate to control plasma in vitro caused a 5% increase in PZC when hemoglobin concentrations reached 1.18 ± 0.10 g/L. In addition, serum samples from a population nutritional survey were scored for hemolysis and analyzed for changes in SZC; samples with hemolysis in the range of 1–2.5 g hemoglobin/L showed an estimated increase in SZC of 6% compared with nonhemolyzed samples. Each approach indicated that a 5% increase in PZC/SZC occurs at ∼1 g hemoglobin/L in plasma or serum. This concentration of hemoglobin can be readily identified directly by chemical hemoglobin assays or indirectly by direct spectrophotometry or matching to a color scale.Conclusions: A threshold of 1 g hemoglobin/L is recommended for PZC/SZC measurements to avoid increases in zinc caused by hemolysis. The use of this threshold may improve zinc assessment for monitoring zinc status and nutritional interventions.

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Section: Introductionmentioning

confidence: 99%

Identification of a Hemolysis Threshold That Increases Plasma and Serum Zinc Concentration

Killilea¹,

Rohner²,

Ghosh

et al. 2017

The Journal of Nutrition

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“…During this period, they were allowed to drink no more than 250 ml of water, sugar-free carbonated drink, coffee, or tea and they refrained from any food. Blood samples were kept at 4°C, and a portion of the sample was separated for baseline erythrocyte zinc and hematocrit measurements before centrifugation [5]. Plasma and whole blood were stored at )80°C until assayed.…”

Section: Materials and Methods Control Subjects And Loading Testmentioning

confidence: 99%

“…The coefficients of variation of copper and zinc analyses using control samples (unassayed chemistry control serum for zinc and copper, Bio-Rad, Richmond, CA) were less than 4% in our laboratory [5], and the differences in the estimated values of copper and zinc in the standard reference material (#1598: National Institute of Standard and Technology, Gaithersburg, MD) were 8% and 6%, respectively. Plasma ceruloplasmin concentration was measured using a radial immunodiffusion kit (Binding Site, San Diego, CA).…”

Section: Laboratory Analyses and Statisticsmentioning

confidence: 96%

“…Plasma copper and plasma and erythrocyte zinc concentrations were assayed by flame atomic-absorption spectrophotometric method [5]. The coefficients of variation of copper and zinc analyses using control samples (unassayed chemistry control serum for zinc and copper, Bio-Rad, Richmond, CA) were less than 4% in our laboratory [5], and the differences in the estimated values of copper and zinc in the standard reference material (#1598: National Institute of Standard and Technology, Gaithersburg, MD) were 8% and 6%, respectively.…”

Section: Laboratory Analyses and Statisticsmentioning

confidence: 99%

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Oral copper loading test in humans

Rahmaniyan

Johnston

Tamura

2003

J Trace Elements Exper Med

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There has been no report of normal responses of plasma copper and/or ceruloplasmin concentrations after an oral loading dose of unlabeled copper in humans. To establish a normal plasma response curve following an oral dose, we performed a copper‐loading test (10 mg elemental copper as copper sulfate) in six healthy adult subjects and monitored plasma copper and ceruloplasmin concentrations for 3.5 h. We found that there were no significant changes in plasma copper and ceruloplasmin concentrations following the oral dose in the subjects. The test was originally intended to evaluate whether there was copper malabsorption in a female patient who developed signs of copper deficiency with her plasma copper levels below 3.0 μmol/l after multiple gastrointestinal surgeries. She did not respond to oral copper sulfate administration but responded to a sublingual application of copper glycinate. These findings suggest that she does not have adequate intestinal copper absorption. In conclusion, the use of unlabeled copper, such as copper sulfate, for an oral loading test, seemingly simple and economical, does not appear to be a suitable means to evaluate copper absorption in humans and is discouraged. In case of copper malabsorption, sublingual administration of copper may be worth trying. J. Trace Elem. Exp. Med. 16: 61–66, 2003. © 2003 Wiley‐Liss, Inc.

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“…15 What all methods of zinc measurement have in common is, that they are prone to influences from preanalytic factors like time elapsed between blood collecting and analysis or zinc contaminations during the process of blood collecting. [16][17][18][19][20][21][22] In this study, we describe the validation of the LT-SYS colometric zinc in vitro diagnostic assay on a Roche cobas c502 analyzer, which is part of a Roche cobas 8000 automated modular platform in the University Clinic Halle (UKH). To date Roche has no zinc assay in its analytic portfolio, rendering it necessary to use third party zinc assays, which are often provided by small to medium scale companies.…”

Section: Introductionmentioning

confidence: 99%

Measuring zinc on the Roche cobas c502 analyzer—Validation, comparison, and pre‐analytic aspects

Kraus

Ludwig-Kraus

2017

Clinical Laboratory Analysis

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Objectives: Characterization of an in vitro diagnostic zinc assay (LT-SYS) on a Roche cobas c502 analyzer and evaluation of the influence of pre-analytic factors on zinc concentration measurements.Design and methods: Imprecision, bias, linearity, limit of blank (LoB), and limit of detection (LoD) were established and method comparisons were performed based on the respective CLSI guidelines. The influence of time elapsed until analysis, the usage of a pneumatic tube delivery system (PTDS) and of special trace element sample tubes was evaluated as well. Results:Estimates of imprecision ranged from 0.9% to 5.0% and bias was low with 1.3% and 1.5% deviation from target value. Linearity was met for the measuring range of 1.15-34.7 μmol/L (7.51-226.9 μg/dL), LoB and LoD were 0.17 μmol/L (1.11 μg/dL) and 0.73 μmol/L (4.77 μg/dL) respectively. The method comparison revealed an average deviation of 8.44% (y=0.542+1.036x). Plasma samples had 7.3% higher zinc values than serum samples on the average. Zinc values of uncentrifuged serum and plasma samples increased 20% in 8 hours, while after centrifugation no significant increase could be detected. Usage of PTDS increased zinc values by 17% and usage of trace element sample tubes showed no advantage over normal ones. Conclusions:The LT-SYS zinc assay showed a fully acceptable performance with good degrees of imprecision and bias, no deviation from linearity and both a very low LoB and LoD. Samples for zinc analysis should be centrifuged timely and transport over PTDS should be avoided. K E Y W O R D Sclinical chemistry, method comparison, method validation, Roche cobas c502, zinc

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Refrigeration of blood samples prior to separation is essential for the accurate determination of plasma or serum zinc concentrations

Cited by 42 publications

References 22 publications

Identification of a Hemolysis Threshold That Increases Plasma and Serum Zinc Concentration

Identification of a Hemolysis Threshold That Increases Plasma and Serum Zinc Concentration

Oral copper loading test in humans

Measuring zinc on the Roche cobas c502 analyzer—Validation, comparison, and pre‐analytic aspects

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