Relationship between a Urine Protein-to-creatinine Ratio of 150 mg/gram Creatinine and Dipstick Grade in the Health Checkup: Substantial Number of False-negative Results for Chronic Kidney Disease.

OBJECTIVE

Proteinuria is a marker for cardiovascular diseases and all-cause mortality. In the Specific Health Checkups in Japan, when subjects show trace proteinuria (grade±) on dipstick assay, further examination is recommended to them. Although 150 mg/gCr is a threshold for diagnosing chronic kidney disease (CKD), little data on the relationship between dipstick grade± and the protein-creatinine ratio have been reported.

METHODS

A cross-sectional study using urine specimens obtained in a single institute, JCHO Saitama Northern Medical Center, was performed from October 2014 to March 2016. The level of proteinuria was measured in fresh morning urine samples from 819 volunteer participants of the Specific Health Checkups by two methods: Eiken Uropaper III to detect and qualitatively grade proteinuria, and total protein concentration by the pyrogallol red method.

RESULTS

Sensitivity, specificity, and the positive likelihood ratio to detect proteinuria of 30 mg/dL by 1+ were 90.3%, 97.8%, and 41.9, whereas 150 mg/gCr by ± were 45.3%, 81.4%, and 2.4, respectively. Therefore, screening for 150 mg/gCr by dipstick grade± had a false-negative rate of 54.7% and false-negative rate was significantly higher in women (8.0%) than in men (1.7%) (p < 0.0001).

CONCLUSIONS

Although the dipstick assay is useful to detect clinically significant proteinuria, substantial numbers of false-negative results occur in checkups for identifying subjects with a risk of CKD.