Combining the use of dipstick protein and specific gravity accurately predicts pathological proteinuria in Japan

UNLABELLED: Dipstick urine analysis is the most common and convenient examination in routine health care. The criteria for abnormal proteinuria is a level of more than (+). However, the interference of urine concentration should be considered in the judgement. OBJECTIVE: The purpose is to demonstrate the effect of the combined use of specific gravity (SG) in the dipstick judgement to evaluate pathological proteinuria in Japanese people. METHODS: The hospital laboratory database of Kitano hospital was searched for urine samples, for patients consulted at our nephrology department from Oct. 2004 to Sep. 2005 (n=1767), and simultaneously assayed for dipstick proteinuria(DSP), SG, urinary protein, urine creatinine (UC) and urinary protein-creatinine ratio (UPC ratio). To generate a model table, samples were stratified according to DSP and SG values. A DSP versus SG matrix (5 x 6)was created, and then all 30 cells were color-coded by the pathological proteinuria proportion (white: or =300 mg/gCr. Moreover in the patients, both 1.005 < SG < or = 1.010 and DSP(+/-), 21/32 (65.6%) had pathological proteinuria. We confirmed the consistency for this combination table in the urine samples of another 1111 out-patients. Moreover, the area under the curve in DSP(+/-) suggests that the patients whose SG was < or = 1.011 might have pathological proteinuria (sensitivity; 82.1%, specificity; 89.3%). CONCLUSION: We recognized that the combination of DSP and SG enhances a more accurate proteinuria judgement. DSP(- approximately +/-) in diluted urine (SG < or = 1.1011) has the potential for pathological proteinuria. Therefore, diluted urine samples should be re-examined.