Variability in snow-urine assays

1995 ◽  
Vol 73 (3) ◽  
pp. 427-432 ◽  
Author(s):  
P. J. White ◽  
R. A. Garrott ◽  
D. M. Heisey
Keyword(s):  
Dietary Intake ◽  
Urinary Metabolites ◽  
Accurate Estimate ◽  
Urine Samples ◽  
Total Variance ◽  
Sample Collection ◽  
Short Term ◽  
Urea Nitrogen ◽  
Measurement Variability ◽  
Dilution Effects

Urea nitrogen: creatinine ratios in snow urine have become popular for assessing the extent of winter nutritional deprivation in ungulates. During winter 1992 – 1993, we collected 10–17 sequential snow-urine samples (402 total) from 27 individually identifiable free-ranging adult female elk. Within-animal variance accounted for 91% of the total variance (351.66 mg2/dL2) in creatinine, 86% of the total variance (637.03 mg2/dL2) in urea nitrogen, and 82% of the total variance (0.56) in urea nitrogen: creatinine ratios. This substantial within-animal variability was unexpected and led to experiments that examined whether the variability was due to sample collection and measurement technique or actually reflected biological variability. Factors examined included dilution effects, measurement (assay) repeatability, and short-term (<24 h) within-animal constancy in metabolite excretion. No dilution effects were detected when the initial concentrations of snow-urine samples were diluted <75% with water. Measurement variability accounted for 0.78, 0.37, and 27.7% of the total variance in creatinine, urea nitrogen, and urea nitrogen: creatinine ratios, respectively. Within-animal metabolite excretion was reasonably constant within 24 h, suggesting that creatinine provides a valid index for comparing urinary metabolites. We conclude that variability in urea nitrogen: creatinine ratios due to dilution, measurement variability, and short-term temporal variability in metabolite excretion was small compared with the total within-animal variance. Urea nitrogen: creatinine ratios should provide an accurate estimate of the true ratios of these metabolites in an elk's bladder urine. However, the interpretation of urea nitrogen: creatinine ratios is often complex, since they reflect the immediate dynamics between fat depletion, protein catabolism, and dietary intake. Differences in ratios between collections may be partially due to variations in recent dietary intake or restriction, in addition to true differences in long-term nutritional status. The best method for statistically analyzing snow-urine data remains unresolved.

Equine Metabolites of Norethandrolone: Synthesis of a Series of 19-Nor-17α-pregnanediols and 19-Nor-17α-pregnanetriols

2003 ◽  
Vol 56 (8) ◽  
pp. 829 ◽  
Author(s):  
Andrew R. McKinney ◽  
Damon D. Ridley ◽  
Peter Turner
Keyword(s):  
Anabolic Steroid ◽  
Metabolic Pathways ◽  
Urinary Metabolites ◽  
Urine Samples ◽  
Ethynyl Group ◽  
Stereoselective Reduction ◽  
Critical Step ◽  
Subsequent Modification

A range of 19-nor-17α-pregnanediols and 19-nor-17α-pregnanetriols have been synthesized and used to confirm the structures of major equine urinary metabolites of the synthetic anabolic steroid norethandrolone (1). 19-Nor-5α,17α-pregnane-3α,17β-diol (2), 19-nor-5α,17α-pregnane-3β,17β-diol (4), 19-nor-5β,17α-pregnane-3α,17β-diol (6), and 19-nor-5β,17α-pregnane-3β,17β-diol (7) were prepared by stereoselective reduction of the 3-ene-4-one of norethandrolone. The 19-nor-5α,17α-pregnane-3β,16α,17β-triol (8) and 19-nor-5α,17α-pregnane-3β,16β,17β-triol (9) were prepared from 19-nortestosterone (11) by multistep processes in which the critical step involved Grignard additions to 16-acetoxy-17-ones. The triols (20R)-19-nor-5α,17α-pregnane-3β,17β,20-triol (22) and (20S)-19-nor-5α,17α-pregnane-3β,17β,20-triol (23) were prepared from norethindrone (24) by initial selective A-ring reduction, then subsequent modification of the 17-ethynyl group. By comparison of these compounds with post-administration equine urine samples it was possible to establish A-ring reduction with 3β,5α stereochemistry as well as non-stereospecific 16-hydroxylation and 20-hydroxylation as significant metabolic pathways affecting norethandrolone in the horse.

Aerosol Analysis Using Handheld Raman Spectrometer: On-site Quantification of Trace Crystalline Silica in Workplace Atmospheres

2021 ◽  
Author(s):  
Shijun Wei ◽  
Belinda Johnson ◽  
Michael Breitenstein ◽  
Lina Zheng ◽  
John Snawder ◽  
...  
Keyword(s):  
Crystalline Silica ◽  
Breathing Zone ◽  
Sample Collection ◽  
Short Term ◽  
Limit Of Quantification ◽  
Measurement Capability ◽  
Matrix Interferences ◽  
Raman Spectrometer ◽  
Quantitative Measurements ◽  
Shift Analysis

Abstract A method for aerosol chemical analysis using handheld Raman spectrometer has been developed and its application to measurement of crystalline silica concentration in workplace atmosphere is described. The approach involves collecting aerosol as a spot sample using a wearable optical aerosol monitor, followed by direct-on-filter quantitative analysis of the spot sample for crystalline silica using handheld Raman spectrometer. The filter cassette of a commercially available optical aerosol monitor (designed to collect aerosol for post-shift analysis) was modified to collect 1.5-mm-diameter spot sample, which provided adequate detection limits for short-term measurements over a few tens of minutes or hours. The method was calibrated using aerosolized α-quartz standard reference material in the laboratory. Two Raman spectrometers were evaluated, one a handheld unit (weighing less than 410 g) and the other a larger probe-based field-portable unit (weighing about 5 kg). The lowest limit of quantification for α-quartz of 16.6 μg m−3 was obtained using the handheld Raman unit at a sample collection time of 1 h at 0.4 l min−1. Short-term measurement capability and sensitivity of the Raman method were demonstrated using a transient simulated workplace aerosol. Workplace air and personal breathing zone concentrations of crystalline silica of workers at a hydraulic fracturing worksite were measured using the Raman method. The measurements showed good agreement with the co-located samples analyzed using the standard X-ray powder diffraction (XRD) method, agreeing within 0.15–23.2% of each other. This magnitude of difference was comparable to the inter- and intra-laboratory analytical precision of established XRD and infrared methods. The pilot study shows that for silica-containing materials studied in this work it is possible to obtain quantitative measurements with good analytical figures of merit using handheld or portable Raman spectrometers. Further studies will be needed to assess matrix interferences and measurement uncertainty for several other types of particle matrices to assess the broader applicability of the method.

Short-term variability of bisphenols in spot, morning void and 24-hour urine samples

2021 ◽  
Vol 268 ◽  
pp. 115747 ◽  
Author(s):  
Celine Gys ◽  
Michiel Bastiaensen ◽  
Govindan Malarvannan ◽  
Yu Ait Bamai ◽  
Atsuko Araki ◽  
...  
Keyword(s):  
Urine Samples ◽  
Short Term ◽  
Short Term Variability

scholarly journals Estimating 24-Hour Sodium Excretion from Spot Urine Samples in Chinese Adults: Can Spot Urine Substitute 24-Hour Urine Samples?

Nutrients ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 798
Author(s):  
Jianwei Xu ◽  
Jiyu Zhang ◽  
Min Liu ◽  
Yamin Bai ◽  
Xiaolei Guo ◽  
...  
Keyword(s):  
Sodium Excretion ◽  
Population Level ◽  
Relative Difference ◽  
Urine Samples ◽  
Misclassification Rate ◽  
Absolute Difference ◽  
Sample Collection ◽  
Spot Urine ◽  
Individual Level ◽  
Chinese Populations

Several estimating equations for predicting 24-h urinary sodium (24-hUNa) excretion using spot urine (SU) samples have been developed, but have not been readily available to Chinese populations. We aimed to compare and validate the six existing methods at population level and individual level. We extracted 1671 adults eligible for both 24-h urine and SU sample collection. Mean biases (95% CI) of predicting 24-hUNa excretion using six formulas were 58.6 (54.7, 62.5) mmol for Kawasaki, −2.7 (−6.2, 0.9) mmol for Tanaka, −24.5 (−28.0, −21.0) mmol for the International Cooperative Study on Salt, Other Factors, and Blood Pressure (INTERSALT) with potassium, –26.8 (−30.1, −23.3) mmol for INTERSALT without potassium, 5.9 (2.3, 9.6) mmol for Toft, and −24.2 (−27.7, −20.6) mmol for Whitton. The proportions of relative difference >40% with the six methods were nearly a third, and the proportions of absolute difference >51.3 mmol/24-h (3 g/day salt) were more than 40%. The misclassification rate were all >55% for the six methods at the individual level. Although the Tanaka method could offer a plausible estimation for surveillance of the population sodium excretion in Shandong province, caution remains when using the Tanaka formula for other provincial populations in China. However, these predictive methods were inadequate to evaluate individual sodium excretion.

scholarly journals Evaluation of Saliva Stability for NMR Metabolomics: Collection and Handling Protocols

Metabolites ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 515
Author(s):  
Daniela Duarte ◽  
Beatriz Castro ◽  
Joana Leonor Pereira ◽  
Joana Faria Marques ◽  
Ana Luísa Costa ◽  
...  
Keyword(s):  
Metabolic Profile ◽  
Room Temperature ◽  
Clinical Laboratory ◽  
Sample Collection ◽  
Short Term ◽  
General Stability ◽  
Sample Stability ◽  
Choline Esters ◽  
Different Temperatures ◽  
Term Storage

Maintaining a salivary metabolic profile upon sample collection and preparation is determinant in metabolomics. Nuclear magnetic resonance (NMR) spectroscopy was used to identify metabolite changes during short-term storage, at room temperature (RT)/4 °C/−20 °C, and after sample preparation, at RT/4 °C (mimicking typical clinical/laboratory settings). Interestingly, significant metabolic inter-individual and inter-day variability were noted, probably determining sample stability to some extent. After collection, no changes were noted at −20 °C (at least for 4 weeks). RT storage induced decreases in methylated macromolecules (6 h); lactate (8 h); alanine (12 h); galactose, hypoxanthine, pyruvate (24 h); sarcosine, betaine, choline, N-acetyl-glycoproteins (48 h), while acetate increased (48 h). Less, but different, changes were observed at 4 °C, suggesting different oral and microbial status at different temperatures (with a possible contribution from inter-individual and inter-day variability), and identifying galactose, hypoxanthine, and possibly, choline esters, as potential general stability indicators. After preparation, addition of NaN3 did not impact significantly on saliva stabilization, neither at RT nor at 4 °C, although its absence was accompanied by slight increases in fucose (6.5 h) and proline (8 h) at RT, and in xylose (24 h) at 4 °C. The putative metabolic origins of the above variations are discussed, with basis on the salivary microbiome. In summary, after collection, saliva can be stored at RT/4 °C for up to 6 h and at −20 °C for at least 4 weeks. Upon preparation for NMR analysis, samples are highly stable at 25 °C up to 8 h and at 4 °C up to 48 h, with NaN3 addition preventing possible early changes in fucose, proline (6–8 h), and xylose (24 h) levels.

Twelve-Hour Urine Collection Can Be Utilized to Estimate 24-Hour Total Urinary Nitrogen in Critically Trauma Patients

2019 ◽  
Vol 152 (Supplement_1) ◽  
pp. S1-S1
Author(s):  
Hsuan-Chieh Liao ◽  
Grant O’Keefe ◽  
Fred Woo ◽  
Lisa Lawrence ◽  
Geoffrey Baird
Keyword(s):  
Correlation Coefficients ◽  
Urine Samples ◽  
Trauma Patients ◽  
Urine Collection ◽  
Sample Collection ◽  
Icu Patients ◽  
Nitrogen Levels ◽  
Significant Difference ◽  
Regression Slopes ◽  
Urinary Nitrogen

Abstract Patients suffering from trauma, burns, and sepsis are frequently in a hypermetabolic state, and as the majority of urinary nitrogen comes from amino acid metabolism, the determination of total urinary nitrogen (TUN) provides an accurate measurement of all nitrogen excreted in urine and can be used as an indicator of catabolic stress. To evaluate whether time of collection influences the performance of TUN test, 12-hour urine specimens were collected from ICU trauma patients and the 12-hour results were correlated with results from 24-hour collections. Two consecutive 12-hour urine samples were collected (06:00-18:00 hours and 18:00-06:00 hours) from surgical ICU patients. Total urinary nitrogen levels were measured in each 12-hour sample, as well as in a pooled sample (24 hours). Pyrochemiluminescence was used to determine TUN level on an Antek 9000N elemental analyzer. In this approach, the urine sample is completely oxidized at high temperature in a quartz pyrotube. Nitrogen is converted to nitric oxide (·NO), then mixed with O3 (ozone) to form nitrogen dioxide (NO2). Light is emitted and specific wavelengths between 650 and 900 nm were measured in a photomultiplier tube. The measured chemiluminescent emission is specific and proportional to the amount of nitrogen in the sample. Fifty 12-hour urine samples from 16 patients were collected. One patient was excluded from the study due to acute renal injury during the collection period. There was no significant observed circadian effect on measured TUN. The 12-hour TUN (g/total volume) was multiplied by 2 to compare to 24-hour TUN for statistical analysis. There was strong correlation between either day or night 12-hour TUN and corresponding pooled 24-hour TUN, with correlation coefficients ranging from 0.93 to 0.98 and regression slopes ranging from 0.98 to 1.01. No statistically significant difference was found between the 12-hour TUN and 24-hour TUN approaches. A 12-hour TUN collection was overall highly predictive of 24-hour TUN collection and has the advantage of convenience of sample collection and improved clinical efficiency. Serial 12-hour urine collection is therefore preferred for monitoring nitrogen balance and adjusting protein intake for critically ill ICU patients.

Short-term biological variation of plasma analytes in renal disease.

1983 ◽  
Vol 29 (3) ◽  
pp. 508-510 ◽  
Author(s):  
C G Fraser ◽  
P Williams
Keyword(s):  
Creatine Kinase ◽  
Renal Function ◽  
Renal Disease ◽  
Potassium Chloride ◽  
Alanine Aminotransferase ◽  
Impaired Renal Function ◽  
Biological Variation ◽  
Total Variance ◽  
Healthy Individuals ◽  
Short Term

Abstract Analytical, intra-individual, and inter-individual components of variation were estimated from duplicate analyses of 11 plasma analytes in an average of 13 specimens obtained, over a two-day period, from nine patients with impaired renal function. Analytical variance was 17.3% of the total variance for sodium; less than 5% of the total variance for potassium, chloride, bicarbonate, albumin, and calcium; and less than 1% for urea, creatinine, glucose, creatine kinase (EC 2.7.3.2), and alanine aminotransferase (EC 2.6.1.2). Average intra-individual variances were of the same order as those found in healthy individuals. All analytes except glucose showed strong individuality. We postulate that, in nonacute pathological processes where new homeostatic steady states are reached, biological variations around the new set points are of the same order as those found in healthy individuals.

THC and CBD concentrations in blood, oral fluid and urine following a single and repeated administration of “light cannabis”

2020 ◽  
Vol 58 (5) ◽  
pp. 682-689 ◽  
Author(s):  
Roberta Pacifici ◽  
Simona Pichini ◽  
Manuela Pellegrini ◽  
Maria Concetta Rotolo ◽  
Raffaele Giorgetti ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Oral Fluid ◽  
Repeated Administration ◽  
Urine Samples ◽  
Gas Chromatography Mass Spectrometry ◽  
Sample Collection ◽  
Valuable Alternative ◽  
The Mean ◽  
Single And Repeated Administration

AbstractBackground“Light cannabis” is a product legally sold in Europe with Δ9-tetrahydrocannabinol (THC) concentration lower than 0.2% and variable cannabidiol (CBD) content. We studied THC and CBD excretion profiles in blood, oral fluid (OF) and urine after smoking one or four light cannabis cigarettes.MethodsBlood, OF and urine samples were obtained from six healthy light cannabis consumers after smoking one 1 g cigarette containing 0.16% THC and 5.8% CBD and from six others after smoking four 1 g cigarettes within 4 h. Sample collection began 0.5 and 4.5 h after smoking one or four cigarettes, respectively. Cannabinoid concentrations were quantified by gas chromatography-mass spectrometry (GC-MS).ResultsAt the first collection, the highest THC and CBD concentrations occurred in blood (THC 7.0–10.8 ng/mL; CBD 30.2–56.1 ng/mL) and OF (THC 5.1–15.5 ng/mL; CBD 14.2–28.1 ng/mL); similar results occurred 0.5 h after the last of four cigarettes in blood (THC 14.1–18.2 ng/mL, and CBD 25.6–45.4 ng/mL) and OF (THC 11.2–24.3 ng/mL; CBD 14.4–37.0 ng/mL). The mean OF to blood ratio ranged from 0.6 to 1.2 after one and 0.6 to 1.9 after four light cannabis cigarettes. THC/CBD ratios in blood and OF were never greater than 2. Urinary 11-nor-9-carboxy-THC concentrations peaked 8 h after one and four cigarettes.ConclusionsOF was a valuable alternative to blood in monitoring consumption of light cannabis. Blood and OF THC/CBD concentration ratios, never exceeded 2, possibly providing a useful biomarker to identify light cannabis vs illegal higher THC cannabis use, where THC/CBD ratios are generally greater than 10.

Measurement of urinary constituents with the Astra-8 Multichannel Analyzer.

1980 ◽  
Vol 26 (13) ◽  
pp. 1883-1886 ◽  
Author(s):  
T A Blumenfeld ◽  
B Griffith
Keyword(s):  
Clinical Chemistry ◽  
Urine Samples ◽  
Serum Samples ◽  
Urea Nitrogen ◽  
Multiple Test ◽  
Multichannel Analyzer ◽  
Urine And Serum

Abstract The Beckman Astra-8 is a computerized, discrete-microsample, multiple-test clinical chemistry analyzer. We have examined its capability to measure urine Na+, K+, Cl-, urea nitrogen, glucose, and creatinine and found that (a) the Astra measurements are linear, accurate, and precise in concentration ranges of urine analytes; (b) urine analyte concentrations measured with the Astra correlate well with those by comparison micromethods (p &lt; 0.001); and (c) the Astra has no significant carryover from adjacent urine samples or from adjacent urine and serum samples.

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