title: Methodological evaluation and comparison of five urinary albumin measurements.
abstract: BACKGROUND
  Microalbuminuria is an indicator of kidney damage and a risk factor for the progression kidney disease, cardiovascular disease, and so on. Therefore, accurate and precise measurement of urinary albumin is critical. However, there are no reference measurement procedures and reference materials for urinary albumin.
  
  
  METHODS
  Nephelometry, turbidimetry, colloidal gold method, radioimmunoassay, and chemiluminescence immunoassay were performed for methodological evaluation, based on imprecision test, recovery rate, linearity, haemoglobin interference rate, and verified reference interval. Then we tested 40 urine samples from diabetic patients by each method, and compared the result between assays.
  
  
  RESULTS
  The results indicate that nephelometry is the method with best analytical performance among the five methods, with an average intraassay coefficient of variation (CV) of 2.6%, an average interassay CV of 1.7%, a mean recovery of 99.6%, a linearity of R=1.00 from 2 to 250 mg/l, and an interference rate of <10% at haemoglobin concentrations of <1.82 g/l. The correlation (r) between assays was from 0.701 to 0.982, and the Bland-Altman plots indicated each assay provided significantly different results from each other.
  
  
  CONCLUSIONS
  Nephelometry is the clinical urinary albumin method with best analytical performance in our study.
authors.affiliation: College of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin, People's Republic of China. lr3595@yahoo.com.cn
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Xiao-Fan
authors.initials: XF
authors.lastname: Cui
authors.forename: Dong-Ling
authors.initials: DL
authors.lastname: Zhang
authors.forename: Qing-Hong
authors.initials: QH
authors.lastname: Yang
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Mu
authors.forename: Wen-Jie
authors.initials: WJ
authors.lastname: Pan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000418:Albumins / Q000032:analysis; D000419:Albuminuria / Q000652:urine*; D005260:Female; D017979:Gold Colloid / Q000737:chemistry; D006454:Hemoglobins / Q000032:analysis; D006456:Hemoglobinuria / Q000652:urine; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D012015:Reference Standards; D012044:Regression Analysis; D015203:Reproducibility of Results; D016482:Urinalysis / Q000379:methods* / Q000592:standards*
chemical_list: D000418:Albumins; D017979:Gold Colloid; D006454:Hemoglobins