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Ascorbic acid in urine still compromises urinalysis results

Background The aim of this work was to determine the frequency of ascorbic acid-positive urine samples and to evaluate the potential risk on patient safety. Materials and methods A total of  27,856 samples submitted for urinalysis in previous year were retrospectively analysed from the laboratory in...

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Bibliographic Details
Published in:Annals of clinical biochemistry 2020-01, Vol.57 (1), p.64-68
Main Authors: Nikolac Gabaj, Nora, Miler, Marijana, Unic, Adriana, Milevoj Kopcinovic, Lara, Vrtaric, Alen, Culej, Jelena
Format: Article
Language:English
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Summary:Background The aim of this work was to determine the frequency of ascorbic acid-positive urine samples and to evaluate the potential risk on patient safety. Materials and methods A total of  27,856 samples submitted for urinalysis in previous year were retrospectively analysed from the laboratory information system. Urinalysis was done on Iris IQ200 analyzer using 11-parameter iChem Velocity test strips. Risk analysis combined the impact of potentially erroneous results (due to ascorbic acid interference) on patient safety (severity – S) with their frequency (occurrence – O). Potential risk was identified as high, intermediate and low. Results One thousand one hundred and ninety-nine (4.3%) and 1646 (5.9%) samples were mildly (20 mg/dL, 1+) and highly positive (40 mg/dL, 2+) for ascorbic acid, respectively. Severity (S1 to S5) was assigned to four possible errors: false-negative glucose (U-Glc: S2), blood (U-Hb: S5), nitrite (U-Nit: S4) and bilirubin (U-Bil: S1). Based on the frequency of errors, occurrence was categorized as: O2 for U-Glc, and O3 for U-Bil, U-Nit and U-Hb. The risk analysis matrix revealed that false-negative U-Hb was associated with potentially high risk, false-negative U-Nit with intermediate risk, while false-negative U-Glc and U-Bil were associated with low risk on patient safety. Conclusions Positive ascorbic acid can cause potentially high risk for patient safety by missing positive blood in urine.
ISSN:0004-5632
1758-1001
DOI:10.1177/0004563219882051