Which Urine Sample for Detection of Proteinuria?

The standard practice of screening for proteinuria in the concentrated early morning urine was examined. Protein concentration and dipstick readings were determined in early morning and daytime urines of 56 normal subjects and 110 patients with proteinuria attending a renal clinic. In normal subjects the protein concentration was similar in both urine samples and dipsticks gave the same frequency of false positive results, usually only trace positive. The protein concentration was higher in the daytime urine in 76% of patients. Dipstick readings were similar in 64.5% but higher in the daytime urine in 31% and in the early morning urine in only 4.5%. It is recommended that daytime urine should be screened for proteinuria in patients presenting in out-patient clinics.