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Christchurch, New Zealand

Fairweather A.A.C.,Science and Technical Group | Eason C.T.,Lincoln University at Christchurch | Eason C.T.,Cawthron Institute | Elder P.A.,Steroid and Immunobiochemistry Unit | And 2 more authors.
New Zealand Journal of Zoology | Year: 2013

Cholecalciferol (vitamin D3) is widely used as a vertebrate pesticide in New Zealand. However, cholecalciferol also occurs naturally in animals. Therefore, when trying to determine whether a non-target animal has been exposed to cholecalciferol baits, knowledge of the baseline cholecalciferol concentrations in the animal's plasma and tissue is required. We analysed cattle, sheep, pig, deer, dog and cat plasma and liver samples for the vitamin D3 metabolite 25-hydroxycholecalciferol (25-OHD), a sensitive biomarker for cholecalciferol. Based on these data and a literature search we present 25-OHD reference ranges. We also examined the literature for 25-OHD concentrations in poisoned animals and compared these to the reference ranges. Where plasma and liver samples have 25-OHD concentrations at least four times higher than our reference ranges it is likely that the animal has been exposed to cholecalciferol baits. 25-OHD concentrations 10 times higher than the reference range indicate ingestion of abnormally high amounts of cholecalciferol. © 2013 The Royal Society of New Zealand.

Binfield A.,Christchurch Hospital | Aird C.,Christchurch Hospital | Murdoch D.R.,University of Otago | Elder P.,Steroid and Immunobiochemistry Unit | Walls T.,Microbiology Unit
Journal of Paediatrics and Child Health | Year: 2014

Aims: Vitamin D deficiency is associated with infectious diseases; however, it is not known whether vitamin D levels are affected by acute infection. Our aim was to establish whether 25-hydroxyvitamin D (25OHD) levels taken during an acute bacterial infection are representative of baseline levels. Methods: Thirty children between 6 months and 15 years of age with proven bacterial infections presenting to a tertiary paediatric referral centre had 25OHD levels taken during their acute infection and again 1 month later provided that they had recovered from their infection, had no subsequent infections and had not been taking vitamin supplements. 25OHD levels were measured by liquid chromatography mass spectrometry. Results: Mean 25OHD at enrolment was 67.5 nmol/L (standard deviation (SD) 22.0), and mean 25OHD at 1 month follow up was 72.7 nmol/L (SD 25.8) (paired t-test P = 0.25). C-reactive protein levels were recorded in 29/30 patients at enrolment (mean 85.1 mg/L, SD 83.5) and 25/30 patients at follow-up (mean 4.0 mg/L, SD 3.3) (paired t-test P = 0.002). The ethnicity of the participants was New Zealand European or European Other, 26; Samoan, 2; Maori, 1; and Chinese, 1. Conclusions: In children, 25OHD levels are not affected by acute bacterial infections; 25OHD levels taken during acute bacterial infection are representative of baseline levels. 25OHD levels collected during acute bacterial infection provide reliable information for case-control studies. © 2014 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

Lankes U.,Steroid and Immunobiochemistry Unit | Brennan S.O.,University of Otago | Walmsley T.A.,Canterbury Health Laboratories | George P.M.,Canterbury Health Laboratories
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2015

The increasing availability of liquid chromatography tandem mass spectrometry (LC-MS/MS) in clinical laboratories provides the opportunity to replace or complement present underperforming immuno- and chemometric assays. Amylase and lipase show limited specificity and sensitivity for pancreatic inflammation and lack the capacity of monitoring the disease due to their short half-lives. Previous findings suggested that cleavage products of the pancreatic enzyme carboxypeptidase A could be a more suitable indicator for defining and classifying pancreatic inflammation. The plasma proteins albumin and β-fibrinogen were digested with trypsin and truncated forms (des-Leu-albumin, and des-Gln-β-fibrinogen) quantified against their non-truncated forms by LC-MS/MS. Four hundred fifty eight samples from 83 patients were used to evaluate the novel method and affirm its suitability for detecting acute pancreatitis. A robust, selective, precise and accurate LC-MS/MS method was set up to measure the proportion of truncated proteins. Reference ranges for the proportion of the truncated albumin and β-fibrinogen were from 2% to 9% and 3% to 25%, respectively. Acute pancreatitis patients had values above these ranges and were distinctly separated from reference control individuals. The longer circulating half-lives of albumin and fibrinogen compared to pancreatic enzymes themselves provide the potential to diagnose pancreatitis more specifically over a longer time period, to monitor the course of the disease, and to track recurrent complications. The wide range of the proportion and the differential half-life of both truncated proteins could also be used for assessing the severity of pancreatitis. © 2015 Elsevier B.V.

Lankes U.,Steroid and Immunobiochemistry Unit | Elder P.A.,Steroid and Immunobiochemistry Unit | Lewis J.G.,Steroid and Immunobiochemistry Unit | George P.,Canterbury Health Laboratories
Annals of Clinical Biochemistry | Year: 2015

Background: Extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis is the method of choice when it comes to the accurate quantification of 25-OH-vitamin D in blood samples. It is generally assumed that the addition of exogenous internal standard allows for the determination of the endogenous analyte concentration. In this study we investigated the extraction properties of endogenous and exogenous 25-OH-vitamin D.Methods: Eight samples were used for the evaluation of the extraction procedure and 59 patients samples for a method comparison. The methanol-to-sample ratio (v/v) and the sample-to-hexane ratio (v/v) were varied and the LC-MS/MS signals of endogenous 25-OH-vitamin D3, spiked 25-OH-vitamin D2 and internal standard of the extracts recorded. The optimized ‘in-house’ LC-MS/MS assay was compared to two automated chemiluminescence immunoassays from DiaSorin and Abbott.Results: Mathematical analysis of the data revealed a differential extraction of endogenous 25-OH-vitamin D3, spiked 25-OH-vitamin D2 and non-equilibrated internal standard. Exogenous 25-OH-vitamin D can be measured accurately if a definite methanol-to-sample ratio is used. Endogenous 25-OH-vitamin D is affected by critical quantification issues due to a differential slope in the extraction profile. The actual 25-OH-vitamin D concentration can be one-third above the measured extractable concentration. Results confirm that the ‘in-house’ LC-MS/MS assay provides reproducible 25-OHvitamin D results.Conclusions: Discordant concentrations of 25-OH-vitamin D from LC-MS/MS assays can be caused by selection of suboptimal extraction conditions. Furthermore, a different sample pretreatment or solvent extraction system may result in a different dissociation and extraction yield of endogenous 25-OH-vitamin D and therefore contribute to variations of LC-MS/MS results. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

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