Background: Ascorbic acid can cause false negative results in the detection of urinary hemoglobin (Hb) with reagent test strips. The fully automated urine analyzer URiSCAN SUPER (YD Diagnostics, Korea), which can measure ascorbic acid, was recently developed. We compared the URiSCAN SUPER to the semi-automated urine analyzer URiSCAN PRO II (YD Diagnostics) and evaluated the usefulness of a new reagent strip to detect ascorbic acid.
Methods: A total of 641 urine samples were used to evaluate the agreement between the two analyzers. In addition we performed urine microscopic examinations to investigate the sensitivity and specificity of urinary Hb and white blood cells. We determined the detection limit of urine ascorbic acid. We also determined the positive rate of ascorbic acid and the false negative rate for urinary Hb. Additionally, the interference effect of ascorbic acid for urinary Hb was investigated.
Results:The agreement rate between the two analyzers was greater than 98% for all tests except for urinary specific gravity. The detection limit of urine ascorbic acid was 10 mg/dL. The positive rate of ascorbic acid was 49.8%. The false-negative rate for urinary Hb was 6.0% and 2.8% (P>0.05) in the presence and absence of urine ascorbic acid, respectively.
Conclusions:The performances of the two urine analyzers were comparable. URiSCAN SUPER for the detection of urinary Hb was resistant to interference by ascorbic acid. Since the URiSCAN SUPER performs a fully automated analysis, it would be useful in urine screening.

Keywords: Ascorbic acid, Automation, False negative reactions, Urinalysis, URiSCAN PRO II, URiSCAN SUPER