K/DOQI clinical practice guidelines for chronic kidney disease: Evaluation, classification, and stratification

3–5 year longitudinal follow-up of pediatric patients after acute renal failure

(2000). European Urinalysis Guidelines. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 60, No. sup231, pp. 1-96.

European Urinalysis Guidelines

Urinary protein and albumin excretion corrected by creatinine and specific gravity

The prevalence of childhood obesity has tripled since the middle 1980s and continues to increase.1,2 Overweight children and adolescents are thought to be at greater risk for earlier onset of cardiovascular and renal diseases in adulthood, which represents a major public health concern.3

Obesity and its metabolic consequences lead to endothelial dysfunction and cardiovascular disease.4 Increased urinary albumin excretion (microalbuminuria) is a marker of endothelial dysfunction and reflects renal and systemic endovascular damage.5–7 Microalbuminuria, which was originally used to predict the development of overt diabetic nephropathy in patients with diabetes mellitus,8–10 is now also considered to be an early marker of renal damage in nondiabetic subjects11 and an independent predictor of future cardiovascular disease in the general adult population.12–17 Indeed, some authors have even advocated screening for microalbuminuria and using it as a therapeutic target for identification and treatment of patients at increased risk for future cardiovascular disease.18–20

The association between cardiovascular risk factors and microalbuminuria in children is unclear, and previous studies came to seemingly discrepant conclusions. Studies with referral-based populations of overweight adolescents found that cardiovascular risk factors increased the risk for microalbuminuria,21–23 similar to findings observed among adults. However, studies with community-based populations found that overweight adolescents (with presumably more coexisting cardiovascular risk factors) actually had lower prevalence of microalbuminuria.24,25 To clarify this issue, we set out to determine how weight and cardiovascular risk factors were related to microalbuminuria in a large, nationally representative sample of adolescents in the United States. On the basis of the literature reports described above, we hypothesized that the relationship between cardiovascular risk factors and microalbuminuria might differ among overweight and nonoverweight adolescents.

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Being overweight modifies the association between cardiovascular risk factors and microalbuminuria in adolescents.

Beginning in 1974, the Japanese Ministry of Health Welfare directed the screening of schoolchildren for proteinuria. We studied their procedure and methods in 6197 school children and also evaluated a new urine dipstick that measures albumin concentrations down to about 10 mg/l and creatinine down to about 300 mg/l. We used specimens from adult in- and outpatients to test the accuracy of the dipsticks. Based on the quantitative results, we set as cutoffs or = "150" mg/l or an albumin of I "30" mg/l indicated increased risk of developing or having a genitourinary disorder. The sensitivity/specificity of the protein dipstick was 95.1%/95.5%, and the same for the albumin dipstick was 83.8%/93.8%. The cut-off for the albumin dipsticks probably should be set somewhat lower to reduce the number of false negatives and increase the sensitivity of the dipstick. When we compared the quantitative albumin to the protein dipsticks with the above cut-offs, we found the sensitivity/specificity to be 79.3%/94.4%, i.e., much like the albumin dipstick results. The many reports on the association of albuminuria and risk of renal disease recommend that screening should be done for albumin rather than protein. Based on the data from the school children, we estimate that a dipstick albumin of "30" mg/l is borderline increased risk, and that a protein dipstick of "150" mg/l is the same. If we call the dipstick "10" mg/l albumin, "30" mg/l albumin and the "150" mg/l protein results "low risk," then we estimate the prevalence of albuminuria in the school children to be about 2.1% and proteinuria to be about 4.3%. Children with these values should have a quantitative test for albumin and protein. We also tested a dipstick for creatinine and found increasing values with increasing age in both genders; the older boys had significantly higher creatinine values than the older girls and younger boys. For the albumin/creatinine ratio, we found 6028 children with a ratio of or = 30 mg/g indicating increased risk. The ratio may be more useful owing to the likely reduction of the number of false negatives and false positives.

Takaaki Saambe

Papers

Screening school children for albuminuria, proteinuria and occult blood with dipsticks.