The evidence based practice for optimal sample quality for ammonia measurement

Nikolac, Nora; Omazić, Jelena; Šimundić, Ana Maria

doi:10.1016/j.clinbiochem.2014.05.068

Cited by 41 publications

(29 citation statements)

References 17 publications

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“…In terms of ammonium concentration, sample storage at 0 to −80 °C will reduce, but not halt, spontaneous ammonia generation (Howanitz et al, 1984; Da Fonseca-Wolheim, 1990; Da Fonseca-Wolhelm, 1990). Both rapid increases in temperature and intracellular formation of ice crystals can increase red cell fragility, which can result in hemolysis and increased plasma ammonium concentrations (Nikolac, Omazic & Simundic, 2014; Maranda et al, 2007; El-Khoury, Bunch & Wang, 2012; Patterson et al, 2011). In one study, rate of ammonia increase in whole blood significantly correlated with erythrocyte count and plasma alanine aminotransferase and gamma glutamyltransferase concentrations when blood was stored at 20 °C but not when stored at 0 °C (Da Fonseca-Wolhelm, 1990).…”

Section: Discussionmentioning

confidence: 99%

“…Heparinized whole blood samples stored in ice water for 30 min before centrifugation have significantly less increases in plasma ammonium than those stored at room temperature for 30 min before centrifugation (13 vs. 31%, respectively) (Nikolac, Omazic & Simundic, 2014). Recommendations for handling samples for ammonium measurement include collecting the blood in a stoppered ammonia-free vacuum tube, placing the tube immediately in an ice or ice water bath, and separating the plasma from the sample within 15 min of collection to prevent spontaneous ammonium generation (Barsotti, 2001; Nikolac, Omazic & Simundic, 2014; Association for Clinical Biochemistry, 2012; Dukic & Simundic, 2015; Maranda et al, 2007). Some authors also recommend using a precooled vacuum sample tube to speed the specimen cooling process (Barsotti, 2001; Maranda et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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The effectiveness of cooling conditions on temperature of canine EDTA whole blood samples

Tobias

Serrano

Sun

et al. 2016

PeerJ

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BackgroundPreanalytic factors such as time and temperature can have significant effects on laboratory test results. For example, ammonium concentration will increase 31% in blood samples stored at room temperature for 30 min before centrifugation. To reduce preanalytic error, blood samples may be placed in precooled tubes and chilled on ice or in ice water baths; however, the effectiveness of these modalities in cooling blood samples has not been formally evaluated. The purpose of this study was to evaluate the effectiveness of various cooling modalities on reducing temperature of EDTA whole blood samples.MethodsPooled samples of canine EDTA whole blood were divided into two aliquots. Saline was added to one aliquot to produce a packed cell volume (PCV) of 40% and to the second aliquot to produce a PCV of 20% (simulated anemia). Thirty samples from each aliquot were warmed to 37.7 °C and cooled in 2 ml allotments under one of three conditions: in ice, in ice after transfer to a precooled tube, or in an ice water bath. Temperature of each sample was recorded at one minute intervals for 15 min.ResultsWithin treatment conditions, sample PCV had no significant effect on cooling. Cooling in ice water was significantly faster than cooling in ice only or transferring the sample to a precooled tube and cooling it on ice. Mean temperature of samples cooled in ice water was significantly lower at 15 min than mean temperatures of those cooled in ice, whether or not the tube was precooled. By 4 min, samples cooled in an ice water bath had reached mean temperatures less than 4 °C (refrigeration temperature), while samples cooled in other conditions remained above 4.0 °C for at least 11 min. For samples with a PCV of 40%, precooling the tube had no significant effect on rate of cooling on ice. For samples with a PCV of 20%, transfer to a precooled tube resulted in a significantly faster rate of cooling than direct placement of the warmed tube onto ice.DiscussionCanine EDTA whole blood samples cool most rapidly and to a greater degree when placed in an ice-water bath rather than in ice. Samples stored on ice water can rapidly drop below normal refrigeration temperatures; this should be taken into consideration when using this cooling modality.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effectiveness of cooling conditions on temperature of canine EDTA whole blood samples

Tobias

Serrano

Sun

et al. 2016

PeerJ

View full text Add to dashboard Cite

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“…Delays in blood centrifugation and room temperature storage can lead to increased ammonia due to in vitro generation by ␥-glutamyltransferase (GGT) activity (4,5 ). Traumatic blood collection and hemolysis can increase ammonia, as red blood cells contain a high concentration of ammonia compared to plasma (6 ).…”

Section: Discussionmentioning

confidence: 99%

Critically High Plasma Ammonia in an Adolescent Girl

et al. 2016

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A 12-year-old female patient presented with nonspecific symptoms including fatigue, fever, and headache persisting for approximately 4 months. Plasma ammonia was 230 g/dL (135 mol/L) (critical value Ͼ187 g/dL or 110 mol/L). The patient was referred to a pediatric emergency center for urgent evaluation of hyperammonemia. Plasma and urine amino acid testing was performed to investigate the possibility of a urea cycle disorder; however, all results were normal. Over the following 2 weeks, the patient was treated with intravenous sodium benzoate/sodium phenylacetate and L-arginine to reduce the blood ammonia concentration. However, the patient's ammonia concentration never dropped below 94 g/dL (55 mol/L) (upper limit of reference interval, 80 g/dL or 47 mol/L), with concentrations as high as 296 g/dL (174 mol/L) with inconsistent associations between ammonia concentrations and headaches. During the course of treatment, the patient suffered substantial side effects of intravenous therapy and underwent numerous costly clinical and laboratory investigations. Amino acid investigations were repeated but results remained normal. Given the large fluctuations in blood ammonia concentrations with inconsistent response to intravenous medications, the metabolic service contacted the laboratory to inquire about a possible preanalytical or analytical cause. One week before this query, a community physician also contacted the laboratory regarding hyperammonemia in several patients. However, no obvious preanalytical or analytical errors were discovered despite numerous audits of preanalytical conditions and review of quality control data.

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“…It has been recommended that heparinised or EDTA plasma samples be kept in an ice bath after sampling, centrifuged immediately on arrival at the laboratory, aliquoted and analysed within 15–30 min, for accurate analysis of ammonia 4. Guidelines for the investigation of hyperammonaemia even recommend repeated ammonia sampling to exclude possible artefactual cause of high ammonia values 3.…”

Section: Introductionmentioning

confidence: 99%