The analysis and characterisation of immuno-unreactive urinary albumin in healthy volunteers

Clavant, Steven P; Sastra, Steve A.; Osicka, Tanya M; Comper, Wayne D.

doi:10.1016/j.clinbiochem.2005.10.013

Cited by 33 publications

(32 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The recent report by Brinkman et al (37 ) notes a progressive decline in results by immunonephelometric assay for specimens stored at -20°C, but an even greater decline for results by sizeexclusion chromatography. Those results suggest that the size-exclusion assay is more sensitive to structural changes of albumin during storage than is the immunonephelometric assay, countering a previous hypothesis that analysis by size exclusion is less sensitive to albumin degradation (15,16 ).…”

Section: Discussioncontrasting

confidence: 51%

“…The Ͼ100 amino acid differences should lead goats to develop a diverse repertoire of antibodies directed at multiple sites in human albumin, and it explains how a urine albumin assay using goat antibodies vs human albumin can react with a variety of modified albumins, albumins from other animal species, or albumin fragments. It is not plausible, as recently reported, that there is a modified form of albumin failing to cross-react with 20 different polyclonal antisera (16 ). Those findings are strong evidence that the putative "immunounreactive albumin" actually is a different protein than albumin.…”

Section: Discussionmentioning

confidence: 55%

“…A second source of uncertainty in urine albumin measurement is the lack of agreement of immunoassays for urine albumin with a size-exclusion chromatographic assay, which yields substantially higher values than immunoassays for many specimens from healthy individuals or diabetes patients (15)(16)(17)(18)(19)(20)(21)(22). This bias has been hypothesized to result from modified forms of urinary albumin that are detected by the size-exclusion assay but not by immunoassays.…”

confidence: 99%

See 2 more Smart Citations

Reactivity of Urinary Albumin (Microalbumin) Assays with Fragmented or Modified Albumin

Sviridov¹,

Drake

Hortin³

2008

Clinical Chemistry

View full text Add to dashboard Cite

Background: Controversy exists regarding occurrence and measurement of structural variants of albumin in urine. In this study, we examined cross-reactivity of in vitro modified albumins in assays for urine albumin (microalbumin). Methods: We analyzed albumin modified by reagents, trypsin, or physical treatments or differing in primary sequence (animal albumins) with an immunoturbidimetric assay (Beckman LX20) using goat antiserum and a competitive immunoassay (Siemens Immulite) using a monoclonal antibody. We assessed occurrence of albumin fragments in urine by use of Western blotting of 24 specimens. Results: Chemical modification, modest sequence substitution (gorilla albumin), or cleavage of albumin by cyanogen bromide (CNBr) had little effect on reactivity in the LX20 assay. Albumin extensively cleaved with trypsin retained partial reactivity. The Immulite assay generally was affected more severely by albumin modifications and sequence changes. Western blots of fresh urine specimens or specimens stored at −80 °C showed little albumin fragmentation, but some specimens stored for 3 years at −20 °C had extensively fragmented albumin that was detected by the LX20 but not the Immulite assay. Conclusions: Nearly equivalent reactivity of intact albumin and CNBr fragments in the immunoturbidimetric assay indicates reactivity of antibodies with multiple epitopes throughout albumin. Therefore, it is difficult to abolish reactivity of albumin in this type of urine albumin assay. Differential sensitivity of 2 assays to albumin modification identifies a potential source of assay nonequivalence in measuring urinary albumin, particularly for specimens stored at −20 °C.

show abstract

Section: Discussioncontrasting

confidence: 51%

Section: Discussionmentioning

confidence: 55%

confidence: 99%

See 1 more Smart Citation

Reactivity of Urinary Albumin (Microalbumin) Assays with Fragmented or Modified Albumin

Sviridov¹,

Drake

Hortin³

2008

Clinical Chemistry

View full text Add to dashboard Cite

show abstract

“…All studies to date used urine samples that had been stored for varying durations of time at Ϫ20°C or Ϫ70°C/Ϫ80°C before assessment of urine albumin by HPLC. In some of these studies, immunoreactive albumin was assessed from fresh samples (9,12,16,17 ), whereas others used frozen samples (6,11,13,14 ). In a previous study in which we compared nephelometric values from fresh samples with HPLC values from frozen samples, we found for the normoalbuminuric range that urine albumin assessed by HPLC is a factor of 3 higher than urine albumin assessed by immunonephelometry, and a factor of 1.3 higher in the microalbuminuric range (9 ).…”

Section: Discussionmentioning

confidence: 99%

Apparent Loss of Urinary Albumin during Long-term Frozen Storage: HPLC vs Immunonephelometry

Brinkman¹,

Zeeuw²,

Heerspink³

et al. 2007

Clinical Chemistry

View full text Add to dashboard Cite

Background: Urinary albumin detection by immunonephelometry is decreased by ϳ30% in samples that have been frozen at ؊20°C. An HPLC method for assessment of urinary albumin that detects immunoreactive and immunochemically nonreactive albumin has been introduced as an alternative to immunonephelometry. We investigated whether this technique is affected by sample temperature, particularly freezing. Methods: Urine samples (n ‫؍‬ 295) were collected from the general population (Prevention of Renal and Vascular End-Stage Disease Study). Samples were assessed by both immunonephelometry and HPLC when fresh and after storage at ؊20°C for 4, 8, and 12 months and at ؊80°C for 12 months. Results: With immunonephelometry, storage for 4, 8, and 12 months at ؊20°C resulted in mean (SD) urine albumin changes of ؊21% (29%), ؊28% (29%), and ؊34% (31) (P <0.001 for trend). Storage at ؊80°C resulted in a 5% (19%) change after 12 months of storage (not significant). With HPLC, storage for 4, 8, and 12 months at ؊20°C resulted in urine albumin changes of ؊33% (28%), ؊43% (24%), and ؊55% (21%; P <0.001 vs immunonephelometry). Storage at ؊80°C resulted in a ؊29% (29%) change (P <0.001 vs immunonephelometry). Conclusion: Loss of albumin after freezing urine depends not only on freezing temperature but also on detection method. Detection of albumin by immuno-

show abstract

“…This is particularly significant due to the existence of non-immunoreactive forms of albumin. 24,25,30 Indeed, chip electrophoresis detected more albumin than did immunoassay in urine 23 and in CSF (Fig. 4).…”

Section: Resultsmentioning

confidence: 99%

Chip Electrophoresis as a Method for Quantifying Total Albumin in Cerebrospinal Fluid

Chan

Herold

2009

JALA: Journal of the Association for Laboratory Automation

View full text Add to dashboard Cite

T he cerebrospinal/serum albumin ratio (Q Alb ) is a measure of cerebrospinaleblood barrier permeability, where dysfunctional barriers have been associated with a variety of disease states. Thus, the ability to accurately quantify albumin has critical diagnostic importance. The current work uses chip electrophoresis as an alternative methodology to the conventional immunoassay for quantifying cerebrospinal fluid (CSF) albumin. With variable concentrations of bovine serum albumin normalized to a chicken albumin internal standard, the electrophoresis system demonstrated signal correlation with a best-fit polynomial (R 2 ¼ 0.9993) (concentration range of 7.8e1000 mg/L). Interchip and intrachip variation studies conducted on patient CSF demonstrated coefficient of variations of 0.1e17%. Chip electrophoresis detected an average of 24% greater albumin than the immunoassay in patient CSF samples (n ¼ 58), indicating the ability to detect immunoreactive and non-immunoreactive forms of albumin. Finally, the correlation of CSF albumin concentration to Q Alb determined by chip electrophoresis (r 2 ¼ 0.8683) was comparable with that determined by immunoassay (r 2 ¼ 0.8390). Therefore, this work demonstrates proof-of-principle that chip electrophoresis can serve as an alternative method for quantifying total (immunoreactive and non-immunoreactive) albumin in CSF.

show abstract

The analysis and characterisation of immuno-unreactive urinary albumin in healthy volunteers

Cited by 33 publications

References 20 publications

Reactivity of Urinary Albumin (Microalbumin) Assays with Fragmented or Modified Albumin

Reactivity of Urinary Albumin (Microalbumin) Assays with Fragmented or Modified Albumin

Apparent Loss of Urinary Albumin during Long-term Frozen Storage: HPLC vs Immunonephelometry

Chip Electrophoresis as a Method for Quantifying Total Albumin in Cerebrospinal Fluid

Contact Info

Product

Resources

About