Storage Of Urine Samples Research Articles

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

Microalbuminuria is a predictor of persistent proteinuria, renal failure and cardiovascular disease and therefore accurate determination of urinary albumin concentration is important. We examined the stability of albumin in urine under different conditions of storage, temperature and sample preparation. There was no significant difference in urinary albumin concentration between fresh urine and urine stored at either 4 degrees C or 20 degrees C for up to 7 days. Similarly in urine samples from diabetic patients there was no significant difference in albumin concentration at levels ranging from 1.3 to 1999.3 mg/l between fresh urine at 4 degrees C and urine stored frozen for 1 week, 1 month or 6 months. Neither storage temperature (-20 degrees C or -40 degrees C) nor centrifugation of sample prior to assay made a significant difference to the albumin concentration. Multiple freezing and thawing of urine samples during 6 weeks of storage at -20 degrees C made no difference to albumin concentrations. Storage of urine samples in either polypropylene, polystyrene or borosilicate glass tubes did not result in a significant change in urinary albumin concentration after either 1 week or 1 month at -20 degrees C although, after 1 month of storage, urinary albumin concentrations tended to be lower by an average of approximately 7%. In tubes to which gelatine had been added this was reduced to 4%. We conclude that fresh urine can be kept at 4 degrees C or 20 degrees C for up to 7 days. Frozen urine samples can be stored for up to 6 months before assay without any loss of albumin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

How and how long to store urine samples before albumin radioimmunoassay: a practical response

We used three study protocols to check the dependence of albumin stability, measured by an RIA, on different temperatures, durations, and materials (i.e., assay tubes) of urine storage. Albumin values obtained for samples stored in three types of assay tubes (glass, polystyrene, and polypropylene) throughout the 2 months of the first (prospective) protocol were superimposable. The 24-h storage of six urine samples at room temperature or at 4 degrees C, as well as 72-h storage at 4 degrees C, did not affect the albumin measurement by RIA. After 2 months of storage of these same six urine samples at -20 degrees C, there was still no albumin decrease. A significant albumin decrease occurred (a mean of approximately 5% per year, throughout the range of albumin concentrations tested) when samples stored at -20 degrees C were reassayed by RIA after > or = 2 years (second protocol, retrospective). Finally, 3 of 21 (14.3%) urine pools stored at -20 degrees C for various periods (4-21 months) showed a significant albumin loss after storage; the time of storage as well the decrement rates of these 3 pools differed from each other (third protocol, retrospective). Short- and medium-term (2-6 months) freezing of urine samples at -20 degrees C does not significantly affect the stability of immunoreactive albumin. For longer preservation periods, storage of urine samples at -70 degrees C may be preferable.

Decreases in Albumin/Creatinine and N-Acetylglucosaminidase/Creatinine Ratios in Urine Samples Stored At -20 Degrees C

The effects of storage for 6 months or 2 years at -20 degrees C were studied in urine samples from Type II diabetic patients by assaying albumin by immunoturbidity, N-acetylglucosaminidase (EC 3.2.1.30) by methoxynitrovinylphenol release, and creatinine by the Jaffé method. There were significant decreases (P < 0.001) in albumin/creatinine ratios from 1.14 (0.63-2.98) to 0.83 (0.32-2.12) g/mol (median + interquartile ranges) after 6 months (n = 97), and from 1.64 (0.74-5.72) to 1.00 (0.37-4.54) g/mol after 2 years (n = 89). The percentage of samples with results below the detection limit of the albumin assay (2 mg/L) increased from 5% to 21% after 6 months and from 0% to 34% after 2 years. N-Acetylglucosaminidase/creatinine ratios decreased (P < 0.001) from 520 (358-832) to 380 (263-695) U/mol after 6 months and from 520 (330-865) to 258 (82-462) U/mol after 2 years. The effect of storage was greater in samples with concentrations in the normal range (< 2.5 g/mol for albumin/creatinine, < 500 U/mol for N-acetylglucosaminidase/creatinine). Samples with albumin concentrations more than twice the normal range were still detected as abnormal after storage at -20 degrees C; e.g., 18% were > 5 g/mol (albumin/creatinine) initially, with 17% > 5 g/mol after 6 months of storage. We therefore recommend storage of urine samples at 4 degrees C for no longer than 7 days before assay.

A method for storage of urine samples in the biological monitoring of organic solvents

A method for storage of urine samples in the biological monitoring of organic solvents

Possible explanation for decrease in albumin content during storage of urine samples

Possible explanation for decrease in albumin content during storage of urine samples

Effects of storage time and temperature on measurement of small concentrations of albumin in urine

Abstract Accurate measurement of albumin excretion rates is important in choosing treatment regimens that may reverse early diabetic renal damage. We report here determinations of slight albuminuria ("microalbuminuria") by radioimmunoassay of fresh specimens, frozen aliquots (stored at -20 degrees C for two, eight, and 24 weeks), and refrigerated specimens (stored at 4 degrees C for one, two, and eight weeks). Seven separate analyses were performed on 101 specimens of urine obtained from 37 subjects with insulin-dependent diabetes mellitus and from 10 nondiabetic healthy controls of a similar age. Storage of urine samples at -20 degrees C resulted in significantly lower measurements of microalbuminuria than in fresh urine (ANOVA, corrected for repeated measures: P = 0.01 to 0.0001). In contrast, storage of urine samples at 4 degrees C for as long as eight weeks did not significantly affect urinary albumin results. The pH values of the specimens were minimally altered and were not a likely cause of the decreased albumin values in the frozen specimens. We conclude that urine specimens for microalbuminuria measurements should either be analyzed as fresh specimens or stored at 4 degrees C and assayed as soon as possible.

有機溶剤の生物学的モニタリングのための尿試料の保存と尿中濃度の補正について

有機溶剤の生物学的モニタリングのための尿試料の保存と尿中濃度の補正について

Screening for microalbuminuria in patients with diabetes mellitus: frozen storage of urine samples decreases their albumin content.

The influence of storage on urinary albumin concentration was prospectively studied with use of overnight urine specimens (Albustix negative) from 73 diabetic patients. From each urine sample four aliquots were taken. One was stored at 4 degrees C and assayed within two weeks, the other three were stored at -20 degrees C and assayed within two weeks and after two and six months. Albumin concentration was measured with laser immunonephelometry. The detection limit, 1 mg/L, suffices for the screening of diabetic patients for microalbuminuria. After storage for two and six months at -20 degrees C, significantly lower albumin concentrations were found. The difference was mainly caused by lower concentrations found in urine samples in which a precipitate had formed, which was the case in 22 and 25 samples, respectively. Thus, freezing of urine samples for determination of low concentrations of albumin may yield falsely low results. Urine samples are best stored at 4 degrees C and assayed within two weeks.

Solvolysable deoxycorticosterone conjugates in human urine.

The nature of the urinary conjugate converted by solvolysis, to free unconjugated deoxycorticosterone (DOC) was studied. A comparison of 11 solvolysis techniques has shown that the method employed in this study yielded 86% of the highest yield by any of the techniques tried. Three successive chromatographic systems on paper showed that no appreciable amounts of contaminants were present in the free DOC eluates, following solvolysis. By preparing authentic [3H]DOC sulphate and subjecting it to solvolysis it was shown that more than 90% of the tritiated DOC was recovered, after chromatography of the free DOC extract. This suggests that much of the solvolysable DOC in human urine is present in the form of the sulphate conjugate. The levels of DOC, excreted as the solvolysable conjugate in a variety of urine specimens, were shown to be much higher than those of free DOC, the former being 4-8 to 127 times higher than the amount of the latter. This highly variable ratio suggests that the site of production of solvolysable DOC is different from that for free DOC. The only correlation between free and solvolysable DOC was shown in dexamethasone-suppressed patients, in whom the mean percentage remaining after suppression was 30-6% for free DOC, 24-1% for solvolysable DOC and 22-2% for cortisol. As solvolysable DOC is present in much larger amounts in urine, care is necessary in the storage of urine samples in which free DOC estimates are to be made, as we found that urine specimens left at room temperature for 1 week could show rises of as much as 400% of their starting free DOC levels.

The Determination of 17-OHCS in Urine-with Regard to the Collection and Storage of Urine Samples, the Removal of Endogenous &beta;-Glucuronidase Inhibitors, Contaminants Induced by Medication and the Composition of the Porter-Silber Reagent

The Determination of 17-OHCS in Urine-with Regard to the Collection and Storage of Urine Samples, the Removal of Endogenous &beta;-Glucuronidase Inhibitors, Contaminants Induced by Medication and the Composition of the Porter-Silber Reagent

The preservation and storage of urine samples for the determination of mercury.

The use of various preservatives and storage containers for the sampling of urine and water samples for mercury analysis was evaluated. The results indicated that glass storage containers were preferred over paper or plastic containers and that potassium persulfate, when added to the sample at the time of collection, would preserve the sample for several days without significant losses. Potassium permanganate was found to he unacceptable for preserving mercury in aqueous solution because of the formation of insoluble manganese dioxide.