Abstract
Microalbuminuria is a risk factor for renal failure, stroke, and cardiovascular disease. However, estimating laboratory precision for albumin excretion is problematic because of its highly skewed distribution and the presence of values below assay detection limits. The authors used 781 quality control pairs from 24-hour urine samples collected between 1996 and 1999 in the International Study on Macronutrients and Blood Pressure (INTERMAP) to compare percentage of technical error (%TE), the usual estimate of laboratory precision, with the mean and median values of within-pair coefficients of variation (CVs) for urinary albumin concentration and other urinary variables. In INTERMAP, %TE was larger than mean CV for all variables. Exclusion of potentially mislabeled samples reduced this difference; for example, for sodium, estimates of %TE and mean and median CV were 2.37%, 0.75%, and 0.28%, respectively, for all 781 pairs and 0.84%, 0.48%, and 0.27%, respectively, with possibly mislabeled pairs excluded. For urinary albumin concentration, exclusion of one mislabeled pair changed estimates for %TE and mean CV from 29.6% and 20.8% to 20.6% and 20.6%, while median CV was unchanged at 9.4%. After exclusion of urinary albumin concentration pairs with values below the detection limit, estimates were 15.4%, 11.4%, and 6.4%, respectively. Results indicate that mean and median CV are not equivalent to %TE and that values below the detection limit can markedly affect estimates and should be excluded.
Original language | English (US) |
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Pages (from-to) | 287-294 |
Number of pages | 8 |
Journal | American journal of epidemiology |
Volume | 160 |
Issue number | 3 |
DOIs | |
State | Published - Aug 1 2004 |
Funding
This research was supported by grants R01 HL50490 and R01 HL65461 from the US National Heart, Lung, and Blood Institute; by the Chicago Health Research Foundation; by the Ministry of Education, Science, Sports and Culture (Grant-in-Aid for Scientific Research (A) no. 090357003) of Japan; and by national official agencies in China and the United Kingdom.
Keywords
- Albumins
- Albuminuria
- Clinical laboratory techniques
- Potassium
- Research design
- Sodium
- Urine
ASJC Scopus subject areas
- Epidemiology