Ascorbic acid—A black hole of urine chemistry screening

Unić, Adriana; Gabaj, Nora Nikolac; Miler, Marijana; Culej, Jelena; Lisac, Adrijana; Horvat, Anita; Vrkić, Nada

doi:10.1002/jcla.22390

Cited by 20 publications

(14 citation statements)

References 13 publications

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“…Ascorbic acid begins to interfere with hemoglobin at low concentrations (0.03 mg/ dL), so it can easily cause false-negative results in occult blood test. Adriana Unic et al [3] showed similar results in their study. The immunological method based on antigenantibody reaction is more specific and free from the interference of ascorbic acid.…”

Section: Discussionsupporting

confidence: 76%

Double false-negative traps in urine routine test: a case report

Xiang

Liang

Ren

2020

Journal of Laboratory Medicine

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BackgroundUrinalysis is one of the most commonly performed tests in clinical practice and supplies important information for a series of clinical conditions, including renal and urinary tract diseases. The clinical laboratory often completes urinalysis through the combined use of urinary dry-chemistry and formed-element analyzers. Urine red blood cell (RBC) morphology test is often used to discriminate the source of hematuria by manual microscopy.Case presentationIn this case report, we describe a 39-year-old woman with chronic glomerulonephritis (CGN) who underwent both urine routine test and RBC morphology test. Her RBC count was in the normal range and the occult blood test was negative in routine test, while the RBC morphology test indicated the presence of non-homogeneous hematuria.ConclusionsTherefore, we analyzed the causes of false-negative result on the urine chemical analyzer and the automatic microscope system, respectively.

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Section: Discussionsupporting

confidence: 76%

Double false-negative traps in urine routine test: a case report

Xiang

Liang

Ren

2020

Journal of Laboratory Medicine

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“…AA causes falsely negative results for glucose, blood, nitrite and bilirubin using iChem Velocity urine test strips. 9 With the exception of glucose, other parameters are affected at the lowest positive results for AA (20–40 mg/dL or 1+), while glucose is less sensitive to AA interference (> 40 mg/dL or 2+). Based on these results, four possible errors were identified due to AA interference: falsely negative glucose (U-Glc), blood (U-Hb), nitrite (U-Nit) and bilirubin (U-Bil).…”

Section: Methodsmentioning

confidence: 92%

“…Urinary glucose determined by urine test strip correlates well with values measured using reference method. 9 Bilirubin in urine can be a useful indicator of hepatic damage, especially when battery of hepatic tests is not initially ordered. Several limitations of measurement of bilirubin in urine are already known.…”

Section: Discussionmentioning

confidence: 99%

“…Nowadays, manufacturers claim that test strips are completely or mostly resistant to AA interferences; however, our previously published work demonstrates that AA interference is still a major issue in urinalysis. 9 AA causes false-negative results for glucose, nitrite, bilirubin and blood for Combur-10M (Roche Diagnostics, Germany) and iChem Velocity (Iris Diagnostics, Germany) test strips. Intensity of interference differs significantly between manufacturers.…”

Section: Introductionmentioning

confidence: 99%

“…Intensity of interference differs significantly between manufacturers. 9 In order to maintain patient safety, all risks associated with laboratory testing have to be recognized and evaluated. Additionally, risk evaluation is a requirement for all laboratories accredited according to ISO 15189 standard.…”

Section: Introductionmentioning

confidence: 99%

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Ascorbic acid in urine still compromises urinalysis results

Gabaj¹,

Miler²,

Unić³

et al. 2019

Ann Clin Biochem

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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.

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Chemical Properties of Urine

2023

Urinalysis in the Dog and Cat

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Ascorbic acid—A black hole of urine chemistry screening

Cited by 20 publications

References 13 publications

Double false-negative traps in urine routine test: a case report

Double false-negative traps in urine routine test: a case report

Ascorbic acid in urine still compromises urinalysis results

Chemical Properties of Urine

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