Dataset Information

Stability of urinary albumin and creatinine after 12 months storage at -20?°C and -80?°C.

ABSTRACT:

Background

Increasing albumin to creatinine ratio (ACR) within the normal range is a risk factor for cardiovascular disease in the general population. Clinical and epidemiological studies often store urine samples for long durations prior to ACR assessment. The stability of ACR at the lowest urinary albumin concentrations during prolonged storage has not been previously studied because routine clinical assays can't quantify very low concentrations of albumin.

Aim

To determine the stability of urinary albumin and creatinine over 12 months in samples stored at -20?°C and -80?°C using an assay which enables assessment of previously undetectable levels of albumin and to investigate if additives can be used to prevent urinary albumin degradation.

Method

ACR was measured in 30 urine samples from healthy subjects on the day of collection. Each sample was divided into 5 portions, each receiving a different treatment; alkalisation, protease inhibiter, boric acid, low protein binding tubes and no treatment (control). Samples were stored at -20?°C and -80?°C and ACR was analysed again after 12 months.

Results

Mean (95% CI) percent change in ACR was -34.3% (-47.2 to -21.4; p?ConclusionThe loss in urinary albumin concentration which occurs during storage at -20?°C for 12 months is not prevented by pre-treating samples prior to storage. For accurate determination of albumin concentration or ACR, samples should be stored at -80?°C on day of collection.

SUBMITTER: Chapman DP

PROVIDER: S-EPMC6451166 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Publications

Stability of urinary albumin and creatinine after 12 months storage at -20 °C and -80 °C.

Chapman Daniel P DP Gooding Kim M KM McDonald Timothy J TJ Shore Angela C AC

Practical laboratory medicine 20190322

<h4>Background</h4>Increasing albumin to creatinine ratio (ACR) within the normal range is a risk factor for cardiovascular disease in the general population. Clinical and epidemiological studies often store urine samples for long durations prior to ACR assessment. The stability of ACR at the lowest urinary albumin concentrations during prolonged storage has not been previously studied because routine clinical assays can't quantify very low concentrations of albumin.<h4>Aim</h4>To determine the ...[more]

PMID: 30997374

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Project description:Background and objectivesBecause there is substantial biologic intraindividual variation in albumin excretion, randomized trials of albuminuria-reducing therapies may need multiple urine samples to estimate daily urinary albumin excretion. Mailing spot urine samples could offer a convenient and cost-effective method to collect multiple samples, but urine albumin-to-creatinine ratio stability in samples stored at ambient temperatures for several days is unknown.Design, setting, participants, & measurementsPatients with kidney disease provided fresh urine samples in two tubes (with and without boric acid preservative). Reference aliquots from each participant were analyzed immediately, whereas remaining aliquots were subject to different handling/storage conditions before analysis, including delayed processing for up to 7 days at three different storage temperatures (4°C, 18°C, and 30°C), multiple freeze-thaw cycles, and long-term frozen storage at -80°C, -40°C, and -20°C. We calculated the mean percentage change in urine albumin-to-creatinine ratio for each condition, and we considered samples stable if the 95% confidence interval was within a ±5% threshold.ResultsNinety-three patients provided samples with detectable albuminuria in the reference aliquot. Median (interquartile range) urine albumin-to-creatinine ratio was 87 (20-499) mg/g. The inclusion of preservative had minimal effect on fresh urine albumin-to-creatinine ratio measurements but reduced the changes in albumin and creatinine in samples subject to processing delay and storage conditions. The urine albumin-to-creatinine ratio was stable for 7 days in samples containing preservative at 4°C and 18°C and 2 days when stored at 30°C. It was also stable in samples with preservative after three freeze-thaw cycles and in frozen storage for 6 months at -80°C or -40°C but not at -20°C.ConclusionsMailed urine samples collected with preservative and received within 7 days if ambient temperature is ≤18°C, or within 2 days if the temperature is higher but does not exceed 30°C, are suitable for the measurement of urine albumin-to-creatinine ratio in randomized trials. Preserved samples frozen to -40°C or -80°C for 6 months before analysis also seem suitable.

Project description:ImportanceAlthough cumulative evidence suggests that elevated urinary albumin-to-creatinine ratio (UACR) in the normal range (<30 mg/g) may be associated with an increased risk of mortality, few studies have investigated whether cardiovascular health (CVH) modifies the harmful outcomes of high-normal UACR.ObjectiveTo investigate associations of traditionally normal UACR and CVH with all-cause mortality.Design, setting, and participantsThis cohort study used National Health and Nutrition Examination Survey data from 2005 through 2018 and linked mortality information until 2019. Data were analyzed from March 1 through October 31, 2023. The study included adult participants aged 20 to 79 years with a normal UACR (<30 mg/g) based on Kidney Disease: Improving Global Outcomes criteria.ExposuresThe UACR was treated as a continuous variable and categorized into tertiles delineated as low (<4.67 mg/g), medium (4.67-7.67 mg/g), and high (7.68 to <30 mg/g). Cardiovascular health was assessed using Life's Essential 8 scores and grouped as poor (0-49 points), moderate (50-79 points), and ideal (80-100 points).Main outcomes and measuresMultivariable Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% CIs for associations of UACR with all-cause mortality in total participants and as stratified by CVH groups.ResultsThe study included 23 697 participants (mean [SD] age, 45.58 [15.44] years; 11 806 women [49.7%] and 11 891 men [50.3%]). During the median 7.8 years (range, 4.5-11.1 years) of follow-up, 1403 deaths were recorded. Near-linear associations were observed for continuous UACR and CVH with all-cause mortality. Compared with the low UACR group, high UACR in the normal range showed an increased mortality risk in the moderate and poor CVH groups (CVH [50-79]: HR, 1.54 [95% CI, 1.26-1.89]; CVH [0-49]: HR, 1.56 [95% CI, 1.10-2.20]), with a significant multiplicative interaction of UACR and CVH (P < .001).Conclusions and relevanceThe findings suggest that high UACR within the normal range is associated with a significantly increased risk of all-cause mortality, with the association more pronounced in adults with poor CVH status. These findings highlight the importance of risk management for early kidney dysfunction, particularly among individuals with poor CVH.

Dataset Information

Stability of urinary albumin and creatinine after 12 months storage at -20?°C and -80?°C.

Background

Aim

Method

Results

Publications

Stability of urinary albumin and creatinine after 12 months storage at -20 °C and -80 °C.

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OmicsDI is part of the ELIXIR infrastructure

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Dataset Information

Stability of urinary albumin and creatinine after 12 months storage at -20?°C and -80?°C.

Background

Aim

Method

Results

Publications

Stability of urinary albumin and creatinine after 12 months storage at -20 °C and -80 °C.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Stability of urinary albumin and creatinine after 12 months storage at -20 °C and -80 °C.