title: Selecting the optimum specimen for assessing slight albuminuria, and a strategy for clinical investigation: novel uses of data on biological variation.
abstract: To investigate the optimum specimen for quantifying low, but abnormal, concentrations of albumin in urine, we assessed the analytical and biological components of variation in first morning, random untimed, and 24-h urine specimens from 11 apparently healthy individuals. The results were expressed in terms of albumin concentration, albumin/creatinine ratio, and albumin excretion rate. Analytical methods generally can meet the analytical goal of CV less than or equal to 18%. For reasons detailed herein, we prefer measurement of the albumin concentration in the first morning specimen. Expressing results as an albumin/creatinine ratio has little advantage. Albumin concentrations in first morning urines from 16 diabetic subjects showed larger intra-individual variation than for nondiabetic subjects but clearly fell into two groups: those with consistently normal albumin concentrations in urine and those with abnormal concentrations in some specimens. The intrinsic biological variation of the latter group means that the ideal 100% nosological specificity cannot be achieved with any cutoff point without inclusion of a large proportion of the former. Qualitative testing with a latex-agglutination technique also demonstrates this problem. Use of data on biological variation allows development of an appropriate clinical strategy to investigate diabetic patients.
authors: Department of Biochemical Medicine, Ninewells Hospital and Medical School, Scotland, U.K.
authors: J E
authors: JE
authors: Howey
authors: M C
authors: MC
authors: Browning
authors: C G
authors: CG
authors: Fraser
mesh_terms: D000419:Albuminuria / Q000652:urine*; D003404:Creatinine / Q000652:urine; D003920:Diabetes Mellitus / Q000652:urine; D005260:Female; D006801:Humans; D007841:Latex Fixation Tests; D008297:Male; D012016:Reference Values; D013997:Time Factors
chemical_list: D003404:Creatinine