Storage temperature and differing methods of sample preparation in the measurement of urinary albumin

Collins, A.C.; Sethi, Mieran; Macdonald, Francis A.; Brown, David M.; Gc, Viberti

doi:10.1007/bf02374489

Cited by 52 publications

(25 citation statements)

References 27 publications

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“…Results of the present study are in agreement with previous studies that describe no significant change in uALB concentration after storage at 220uC for up to 6 months. 3,7 However, others detected a decrease of 20% in uALB concentration after 6 months at 220uC. 26 In the present study, uRBP was significantly lower at T 4 months compared with T 0 .…”

Section: Discussioncontrasting

confidence: 51%

Effect of Sampling Method and Storage Conditions on Albumin, Retinol-Binding Protein, And N-Acetyl-β-D-Glucosaminidase Concentrations in Canine Urine Samples

et al. 2010

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Abstract. Urinary markers for renal dysfunction are gaining interest, but effects of sampling method, storage conditions, and urinary tract inflammation or infection on these markers are unclear. Therefore, the objectives of the current study were to determine the difference in urinary albumin (uALB), urinary retinolbinding protein (uRBP), and urinary N-acetyl-b-D-glucosaminidase (uNAG) concentrations in cystocentesis and voided samples and to investigate concentration changes after storage at 220uC and at 280uC. Effects of a protease inhibitor were also assessed in samples stored at 280uC for 12 months. In a pilot experiment, influence of in vitro hematuria, pyuria, and bacteriuria on the urinary markers was evaluated. A mixed model was used to calculate mean differences and 95% confidence intervals. Urinary ALB, uNAG, and uRBP concentrations were similar in voided and cystocentesis samples. After storage for 4 months at 220uC, uALB concentration was not affected, and uRBP concentration showed a mild and clinically irrelevant decrease, whereas uNAG activity was significantly lower compared with fresh samples. After storage for 12 months at 280uC, uALB and uRBP concentrations did not differ from fresh samples, but uNAG activity was severely decreased. Protease inhibitor addition did not preserve uNAG activity. Experimental hematuria, pyuria, and bacteriuria did not seem to affect urinary markers, although further research is needed.

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Section: Discussioncontrasting

confidence: 51%

Effect of Sampling Method and Storage Conditions on Albumin, Retinol-Binding Protein, And N-Acetyl-β-D-Glucosaminidase Concentrations in Canine Urine Samples

et al. 2010

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“…Innanen et al (21 ) and Collins et al (22 ) found no substantial difference after 6 months. Two authors reported no substantial change in UAC after 24 (29 ) and 26 months (30 ); the UACs in those studies, however, were considerably higher than in ours.…”

Section: Clinical Chemistry 51 No 11 2005mentioning

confidence: 91%

“…Moreover, storage tube materials might play a role in preventing albumin loss after freezing. Collins et al (22 ), however, found no difference in concentration when they studied the effect of different tube materials on UAC after freezing. Conformational changes that occur during freezing may lead to loss of the antibody recognition site that is needed to measure albumin with immunochemical methods (22,32 ).…”

Section: Clinical Chemistry 51 No 11 2005mentioning

confidence: 97%

Falsely Low Urinary Albumin Concentrations after Prolonged Frozen Storage of Urine Samples

Brinkman¹,

Zeeuw²,

Duker³

et al. 2005

Clinical Chemistry

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Microalbuminuria, defined as a urinary albumin concentration (UAC) of 20 -200 mg/L, is an early predictor of diabetic nephropathy (1)(2)(3)(4)(5)(6). In addition, microalbuminuria is a marker of cardiovascular morbidity and mortality, both in patients with diabetes mellitus and in the general population (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Consequently, there is great interest in screening for microalbuminuria in these groups. In cohort studies, urine samples are often kept frozen at Ϫ20°C before analysis. Although some study results have indicated no effect of freezing on , other studies have found erroneously low values when samples were frozen at Ϫ20°C (24 -27 ). Only a few studies have investigated the effect of longer storage periods, but these studies were small, and samples were in the macroalbuminuric range (Ͼ200 mg/L).We investigated the effects of storage at Ϫ20°C for up to 24 months, mixing methods, and baseline UAC on samples in the normo-and microalbuminuric ranges.Urine samples were collected during the prospective PREVEND study in the general population initiated to investigate urinary albumin excretion as a predictor of renal and cardiovascular disease (28 ). The participants were asked to collect urine for two 24-h periods and to store it in two 3-L plastic containers at 7°C and deliver it within 2 days to the clinic. Immediately after delivery, the urine sample volume was determined, and a portion of each of the 24-h samples was stored in 2-mL polypropylene aliquots at Ϫ20°C for albumin assessment after freezing. For measurement of UAC in fresh samples, portions were kept at 7°C in 10-mL polystyrene tubes until the UAC was measured.All participants gave written informed consent. The PREVEND study was approved by the local medical ethics committee and was conducted in accordance with the guidelines of the Declaration of Helsinki.On the basis of the fresh UAC and duration of storage, we selected 1785 urine samples for the study. Samples were obtained from storage (Ϫ20°C) 1-3 days before analysis, thawed at 7°C, and randomly assigned to 3 groups. Samples in the first group (I; n ϭ 600) were not mixed before analysis, samples in the second group (II; n ϭ 596) were subjected to 3-4 hand inversions before analysis, and samples in the third group (III; n ϭ 689) were vortex-mixed for 5-10 s. All samples were centrifuged before analysis and analyzed directly after centrifugation. At the time of analysis the samples were at room temperature. Samples were thawed and analyzed in the same laboratory.UAC was measured by immunonephelometry (Dade Behring Diagnostics) with a lower limit of detection of 2.3 mg/L (defined as the concentration of the lowest calibrator solution). The intra-and interassay CVs, evaluated in our laboratory, were 2.7% and 4.5%, respectively.All data were analyzed with SPSS 12.0 software. Data are presented as mean (SD) percentage differences in albumin, which had a gaussian distribution. Differences among groups were assessed by ANOVA, and differences between groups by post hoc a...

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“…A fasting blood sample was taken for measurement of plasma glucose (enzymatic colorimetry), serum total cholesterol (enzymatic colorimetry), and serum creatinine (rate reaction method) using a Cobas Mira Plus analyser (Roche Diagnostics, Basel, Switzerland). Urine creatinine (Jaffe reaction) and urine albumin concentration (by immunoturbidimetry [23]) were determined using a Cobas Mira Plus analyser (Roche Diagnostics). Glycated hemoglobin (HbA 1c ) was measured by boronate affinity high-pressure liquid chromatography (Primus CLC330, Kansas City, MO).…”

Section: Methodsmentioning

confidence: 99%

Aortic Pulse Wave Velocity and Albuminuria in Patients with Type 2 Diabetes

Smith

Karalliedde

Angelis

et al. 2005

Journal of the American Society of Nephrology

125

100

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Development of microalbuminuria increases the risk for cardiovascular disease (CVD) in type 2 diabetes. The nature of this relationship is unclear but may involve arterial stiffness, an independent risk marker for CVD mortality. Aortic pulse wave velocity (Ao-PWV) and albumin creatinine ratio (ACR) were measured in 134 consecutive patients with type 2 diabetes without overt renal impairment (serum creatinine <150 mol/L). ACR ranged from 0.2 to 153 mg/mmol. Patients with raised ACR (>3 mg/mmol) had higher Ao-PWV, poorer diabetic control, and higher pulse pressure (PP) and systolic BP (SBP) (all P < 0.05) than those with normal ACR. The closest univariate associations of Ao-PWV were positively with age, duration of diabetes, SBP, PP, ACR, and insulin treatment and negatively with GFR and weight (all P < 0.01). In a multiple linear step-down regression analysis, the significant predictors of Ao-PWV were age, SBP or PP, duration of diabetes, gender, number of antihypertensive medications, and use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, which together explained 55% of the variance of Ao-PWV. When ACR was offered in place of arterial pressure to a separate model, ACR emerged as a significant predictor of Ao-PWV. After age adjustment, patients with lower, below median GFR had higher Ao-PWV than those with GFR above the median (P ‫؍‬ 0.043). In patients with type 2 diabetes without overt renal impairment, raised ACR is associated with higher Ao-PWV, a relationship most likely mediated by raised BP. The association of Ao-PWV with reduced GFR suggests that even modest renal dysfunction may affect the viscoelastic properties of large arteries.

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Storage temperature and differing methods of sample preparation in the measurement of urinary albumin

Cited by 52 publications

References 27 publications

Effect of Sampling Method and Storage Conditions on Albumin, Retinol-Binding Protein, And N-Acetyl-β-D-Glucosaminidase Concentrations in Canine Urine Samples

Effect of Sampling Method and Storage Conditions on Albumin, Retinol-Binding Protein, And N-Acetyl-β-D-Glucosaminidase Concentrations in Canine Urine Samples

Falsely Low Urinary Albumin Concentrations after Prolonged Frozen Storage of Urine Samples

Aortic Pulse Wave Velocity and Albuminuria in Patients with Type 2 Diabetes

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