Stability of Common Analytes in Urine Refrigerated for 24 H Before Automated Analysis by Test Strips (Hematology‪)‬

Supertron, a fully automated urinalysis system, provides semiquantitative tests for erythrocytes, leukocytes, glucose, protein, and nitrites (1). A counting chamber method for the numbers of erythrocytes and leukocytes has shown a concordance of 86-98% and an excellent correlation with other semi-automated urinalysis systems (1). Despite a maximum throughput of up to 300 test strips per hour, processing large numbers of urine samples arriving in the late afternoon might be difficult. Furthermore, clinics from wide geographical areas serviced by a central laboratory might have difficulty assuring that the urine arrives on the same day as collection. Although urine samples left on the tray for 60 min are stable (1), the stability of a urine sample refrigerated for 24 h is unknown. The insert recommends testing the urine within 2 h of sampling. To determine stability, we compared the precision of paired urinalysis tests done at the same time by automated dipstick analysis (Supertron) to those repeated after a 24-h interval. Materials and Methods