The effect of centrifugation on three urine protein assays: benzethonium chloride, benzalkonium chloride and pyrogallol red.
Author(s): Sürer H, Özgün T, Yilmaz FM, Yilmaz G
Publication: Clin Chem Lab Med, 2014, Vol. 52, Page e71-3
PubMed ID: 24280287 PubMed Review Paper? No
Purpose of Paper
This paper investigated the effects of urine centrifugation, protein level (normal or elevated), and the presence of leukocyte esterase on the measurement of urine protein levels using three different assays as well as creatinine levels.
Conclusion of Paper
Protein levels in urine declined with centrifugation, regardless of the analysis method used, but the magnitude of the decline was largest when specimens had protein levels below 140 mg/L and were analyzed using the benzethonium chloride method. Specimens with leukocyte esterase tended to show larger declines than those without, but the difference was not significant. Creatinine levels were unaffected by centrifugation.
Studies
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Study Purpose
This study investigated the effects of urine centrifugation, protein level (normal or elevated), and the presence of leukocyte esterase on the measurement of urine protein levels using three different assays as well as creatinine levels. Protein and creatinine levels were measured in 112 routine urine specimens before and after centrifugation at 1000 x g for 5 min. Protein levels were measured using the pyrogallol red and benzalkonium chloride assays on an Olympus 640 analyzer and using the benzethonium chloride assay on a Modular P analyzer. Creatinine levels were measured using an Olympus 640 analyzer. Specimens were divided into those with normal protein levels <140 mg/L (53 specimens) or elevated protein levels >140 mg/L (59 specimens) and based on leukocyte esterase positivity using a dipstick test.
Summary of Findings:
Centrifuged urine had significantly lower levels of protein than uncentrifuged urine, regardless of assay (P<0.001 all), but creatinine levels were unaffected by centrifugation. The percentage change in protein levels with centrifugation was dependent on the analysis method used with the largest declines observed using the benzethonium chloride and the smallest using the Pyrogallol red assay. The percentage change was also dependent on protein level with larger declines noted for specimens with a protein level below 140 mg/L than those above 140 mg/L (P<0.05, all). Although specimens that were positive for leukocyte esterase using dipsticks tended to display larger decreases in protein levels with centrifugation than those negative for leukocyte esterase, the difference was not significant.
Biospecimens
Preservative Types
- None (Fresh)
Diagnoses:
- Not specified
Platform:
Analyte Technology Platform Protein Clinical chemistry/auto analyzer Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Preaquisition Biomarker level <140 mg/L protein
>140 mg/L protein
Leukocyte esterase present
Leukocyte esterase absent
Clinical chemistry/auto analyzer Specific Technology platform Benzethonium chloride
Benzalkonium Chloride
Pyrogallol red
Biospecimen Aliquots and Components Centrifugation Centrifuged
Not centrifuged