title: The influence of vitamin C on the urine dipstick tests in the clinical specimens: a multicenter study.
abstract: BACKGROUND
  Vitamin C may interfere with the results of urine dipstick tests. We investigated the incidence of urinary vitamin C and its interference with urine dipstick reagents using a vitamin C dipstick.
  
  
  METHODS
  The incidence of urinary vitamin C was determined in patients and healthy individuals undergoing routine medical check-ups. Interference tests were performed using samples with various amounts of added vitamin C. For clinical samples, we identified false-negative dipstick glucose, hemoglobin, and leukocyte esterase results based on the urine sediment and serum glucose results.
  
  
  RESULTS
  Vitamin C was found in the urine of 18.1% of the subjects overall, and 23.1% of those undergoing medical check-ups. Dipstick results for glucose, leukocyte esterase, and hemoglobin differed between samples without vitamin C and with added vitamin C. When vitamin C was detected in clinical urine samples, 42.3%, 10.6%, and 8.2% of the glucose, hemoglobin, and leukocyte esterase dipstick tests were rated as false negative, respectively.
  
  
  CONCLUSIONS
  Vitamin C was frequently found in clinical urine samples, and its concentration was higher in individuals undergoing medical check-ups. Urinary vitamin C can interfere with the urine dipstick results. This study gives useful information for predicting false-negative rates of urine dipstick tests caused by vitamin C.
authors: Department of Laboratory Medicine, Keimyung University School of Medicine, Daegu, Korea.
authors: Wonmok
authors: W
authors: Lee
authors: Department of Laboratory Medicine, Yeungnam University College of Medicine, Daegu, Korea.
authors: Yukyung
authors: Y
authors: Kim
authors: Department of Laboratory Medicine, Daegu Fatima Hospital, Daegu, Korea.
authors: Soonhee
authors: S
authors: Chang
authors: Department of Laboratory Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea.
authors: A-Jin
authors: AJ
authors: Lee
authors: Department of Laboratory Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea.
authors: Chang-Ho
authors: CH
authors: Jeon
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry* / Q000652:urine*; D002265:Carboxylic Ester Hydrolases / Q000652:urine; D005188:False Negative Reactions; D006029:Glycosuria; D006456:Hemoglobinuria; D006801:Humans; D015203:Reproducibility of Results; D016482:Urinalysis / Q000379:methods / Q000592:standards*
chemical_list: C021443:leukocyte esterase; D002265:Carboxylic Ester Hydrolases; D001205:Ascorbic Acid
keywords: interference; urine dipstick test; vitamin C