[Relevance of urinary protein/creatinine ratio and urinary abnormal casts].
OBJECTIVE
The quantification of 24 hrs urinary protein excretion is valuable for diagnosing and monitoring renal disease. However, because of its practical difficulties, the spot urinary protein/creatinine (P/C) ratio has been utilized. We aimed to evaluate the analytical performance of P/C ratio by comparing with the qualitative urinary protein values and the microscopic urine sediment analysis.


METHODS
We obtained 5,538 urinary samples from the outpatients of Juntendo University Hospital. Testing for urinary P/C ratio was performed by Atlas Pro12 (cut-off 150 mg/g x Cr), urinary protein (proteinuria) was detected quantitatively by full-automated system ATLAS XL (cut-off 30 mg/dL). Microscopic exams were conducted following to the JCCLS reference method.


RESULTS
The P/C ratio demonstrated higher sensitivity but lower specificity for urinary abnormal casts detected by microscopic exams compared to proteinuria (sensitivity; P/C 87%, proteinuria 77%. specificity; P/C 74%, proteinuria 93%). From the comparative study with microscopic exams, both P/C and proteinuria performed high positive rate (> 80%) for the granular cast type and mixture cast type. For the cellular cast type, however, the positive rate of P/C was 56% and that of proteinuria was only 36%. The overall abnormal casts by microscopic exams showed better correlation with the positive P/C ratio than proteinuria.


CONCLUSIONS
This study emphasizes that a spot urine P/C ratio is useful in screening for the further microscopic exams. P/C ratio can be a convincing index of urinary protein excretion when attenuation urine is doubted.
Wakita
Mitsuru
M
Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo 113-8421, Japan.
Tabe
Yoko
Y
Ishii
Kiyoshi
K
Miyake
Kazunori
K
Horii
Takashi
T
Miida
Takashi
T
Osaka
Akimichi
A
D003404:Creatinine / Q000652:urine*; D006801:Humans; D011507:Proteinuria / Q000652:urine*; D012680:Sensitivity and Specificity
D003404:Creatinine