Background: The utility of dipstick proteinuria for predicting microalbuminuria in non-diabetic lifestyle-related diseases
compared with the urine protein-to-creatinine ratio (uPCR) and the effect of dipstick proteinuria on the cut-off
value (CO) and accuracy of uPCR are unclear.
Methods: The subjects included Japanese patients ≥ 18 years old with lifestyle-related diseases who had an estimated
glomerular filtration rate of ≥ 15 ml/min/1.73 m2 and uPCR of < 0.5 g/gCr at initiation. Urine dipstick, uPCR and
urine albumin-to-creatinine ratio (uACR) were measured three times per case. Microalbuminuria was defined as uACR
of 30–299 mg/gCr for at least 2 of 3 measurements. Youden’s Index was used as the optimal CO. Factors associated
with microalbuminuria were analyzed using a logistic regression model.
Results: In 313 non-diabetic cases (median 70.8 years old), 3 dipstick proteinuria measurements were independently
useful for detecting microalbuminuria, and the CO was set when a trace finding was obtained at least 1 of 3 times
(sensitivity 0.56, specificity 0.80, positive predictive value [PPV] 0.73, negative predictive value [NPV] 0.65). A single
uPCR measurement was more useful than 3 dipstick measurements, and was useful for detecting microalbuminuria
even in cases with three consecutive negative proteinuria findings, indicating that the CO of the second uPCR with
G1-3a (n = 136) was 0.06 g/gCr (sensitivity 0.76, specificity 0.84. PPV 0.68, NPV 0.89), while that with G3-b4 (n = 59) was
0.10 g/gCr (sensitivity 0.56, specificity 0.91. PPV 0.83, NPV 0.71). The sum of 3 uPCRs was useful for detecting microalbuminuria
in cases with G1-3a (sensitivity 0.67, specificity 0.94, PPV 0.82, NPV 0.86) and G3b-4 (sensitivity 0.78, specificity
0.94, PPV 0.91 NPV 0.83), with both COs being 0.23 g/gCr. These COs of microalbuminuria did not change when
trace or more proteinuria was included, although the sensitivity increased. A high uPCR and low urine specific gravity
or creatinine level were independent factors for uACR ≥ 30 mg/gCr in cases with negative proteinuria, although the
uPCR was a major predictive factor of a uACR ≥ 30 mg/gCr.
Conclusions: The uPCR (preferably determined using early-morning urine), including in dipstick-negative proteinuria
cases with non-diabetic lifestyle-related diseases, can aid in the early detection of microalbuminuria.
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