Serum zinc concentrations: contamination from laboratory equipment

Toxicology and Analytical Chemistry

Knowing how to effectively use veterinary diagnostic toxicology laboratories is key when navigating suspect toxicoses in ruminants. This begins with establishing a causal relationship between clinical signs and potential sources of exposure, followed by collecting the appropriate samples for toxicology testing. There are times in which a successful diagnosis is hindered by not obtaining a thorough case history and not knowing what specimens to collect, or how much specimen to submit, for toxicology testing. This article is intended to offer some guidance with respect to the effective use of veterinary toxicology/analytical chemistry laboratories when navigating suspect toxicology cases in ruminants.

Preanalytical errors on zinc concentrations caused by single-use gloves

Preanalytical errors causing specimen contamination with zinc (Zn) are disastrous for routine medical diagnostics or scientific studies. The aim of the study presented here is to simulate contamination possibilities when using single-use gloves. The ability to release Zn into the specimen was tested using nitril (A), vinyl (B) and latex (C) gloves with 15 (14) replications. In our first approach, a 1 × 1 cm piece of the glove's fingertip was incubated for 10 min with serum. Our second approach imitated a very short contact of serum to the glove's material by letting serum run over the glove from a pipette for 3 cm distance into a tube. The effect of gloves' contact to liver tissue was examined using glove C only: a block of liver tissue was touched once at one side producing an experimental fingerprint. Zn was analyzed in serum and liver wet weight (ww) using ICP-MS; the basal serum/liver Zn concentration was set as zero for calculation. The calculated addition of Zn is given as median (p25 - p75). The first approach led to distinct contamination with Zn (in μg/L) being evident from all three types of gloves, but depended markedly from the type of material: A: 176.5 (129.7-204); B: 975.1 (663.6-1164.3); C: 2112 (1685-2516). Imitating a very short contact of serum to the glove's surface resulted in an additional Zn concentration of 105.7 (70.4-168.8), 56.2 (-13.5-121.4) and 955.7 (746-1159) μg/L using gloves A, B and C, respectively. A single fingerprint on liver tissue using glove C resulted an addition of 3995 (861-6435) μg Zn/kg liver ww. The data underline that the dimension of preanalytical contamination of blood and tissue samples for Zn analysis via single-use gloves is relevant for routine diagnostics and scientific studies. Critical steps and possibilities to minimize these effects should be considered seriously for specimen handling in routine laboratory diagnostics as well as in scientific studies to avoid preanalytical errors and, finally, misinterpretation of the data.

Random-effects linear model application to herd-level assessment of bovine hepatic trace mineral concentrations

To evaluate the utility of random-effects linear modeling for herd-level evaluation of trace mineral status, we performed a retrospective analysis of the results for trace mineral testing of bovine liver samples submitted to the Michigan State University Veterinary Diagnostic Laboratory between 2011 and 2017. Our aim was to examine random-effects models for their potential utility in improving interpretation with minimal sample numbers. The database consisted of 1,658 animals distributed among 121 herds. Minerals were assayed by inductively coupled plasma-mass spectroscopy, and included cobalt, copper, iron, molybdenum, manganese, selenium, and zinc. Intraclass correlation coefficients for each mineral were significantly different (p < 0.001) from zero and ranged from 0.38 for manganese to 0.82 for selenium, indicating that the strength of herd effects, which are presumably related to diet, vary greatly by mineral. Analysis of the distribution and standard errors of best linear unbiased predictor (BLUP) values suggested that testing 5-10 animals per herd could place herds within 10 percentile units across the population of herds with 70-95% confidence, the confidence level varying among minerals. Herd means were generally similar to BLUPs, suggesting that means could be reasonably compared to BLUPs with respect to the distributions reported here. However, caution in interpreting means relative to BLUPs should be exercised when animal numbers are small, the standard errors of the means are large, and/or the values are near the extremes of the distribution.

Storage and preservation of blood and urine for trace element analysis. A review

In any well-defined study, a sample preservation and storage scheme compatible with the information or analyte sought should be incorporated. This article emphasizes the need for preservation and storage of biological fluids collected for trace element determination; cites the major factors, such as container material, container pretreatment, storage time, storage temperature, and contamination of the laboratory environment affecting preservation; presents a historical account of the available literature studies on the preservation and storage of trace metals in whole blood, plasma, serum, and urine; and makes recommendations on the most effective storage and preservation methods.

Principles of nutrition therapy for short-bowel syndrome

Short-bowel syndrome is characterized by maldigestion, malabsorption, dehydration, electrolyte abnormalities, and both macronutrient and micronutrient deficiencies. Nutritional and hydration status are difficult to maintain without the provision of specialized nutrition support when more than 75% of the small intestine has been resected. Each patient's response to small-bowel resection is unique; therefore, the type of therapy must be tailored to each individual's bowel resection, complications that ensue, and specific nutrient needs. Clinical management should be guided by principles of nutrition assessment and treatment of nutrient deficiencies as well as routine monitoring of the patient's clinical course and response to therapy.

Parenteral administration of trace elements to critically ill patients

Studies of zinc, copper, manganese, chromium, selenium and molybdenum balance were carried out in eight patients in an intensive care unit. In six of these, nickel balance was also measured. The amount of each element in fluid administered to the patients, and the amount lost in urine and gastrointestinal fluid on each of seven days, was measured by atomic absorption spectrometry and cumulative balances calculated. Satisfactory balances of zinc, copper and manganese were obtained when the amounts administered approximated those currently recommended. Chromium balances were variable, while those of molybdenum, selenium and nickel were negative in most patients. Interpretation of balance studies of this type in critically ill patients is made difficult by abnormal renal and gastrointestinal function.