Can we reduce the interference of vitamin C and PH in urinalysis?

FENG, Danqin; LIN, Jinbiao; CAI, Jianguo; CHEN, Xiaoli; YE, Huiming

doi:10.1590/fst.37321

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Food Science and Technology

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Original Article • Food Sci. Technol (Campinas) 42 • 2022 • https://doi.org/10.1590/fst.37321 copy

Can we reduce the interference of vitamin C and PH in urinalysis?

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Urinalysis is often interfered by vitamin C and PH. This study was to evaluate the interference of vitamin C and PH in urinalysis, and minimize the risk to make the effective communication. 732 leftover urine samples in which the concentration of vitamin C was 0.0 mmol/L and either of the test-strip results (Glucose, Blood, Bilirubin, Leucocyte, Nitrite, Protein, Ketone) was positive that were collected. The interference test checked out using these leftover urine samples. When the chemical protein module was positive, the sulfosalicylic acid test performed to confirm the positive results. About 27% of urine samples were vitamin C positive. Adequate vitamin C would interfere with the chemical result of GLU, BIL, and BLD, but not KET, PRO, WBC, NIT (p-value < 0.05). False-positive protein occurred at any samples, but higher when urine PH is greater than or equal to 8.0. In summary, to minimize the risk of vitamin C and PH in urinalysis, the laboratory should pay more attention to its conditions. Also, do more to help guarantee the accuracy of the urinalysis results and to give more comments to doctors to achieve effective communication.

Keywords
: interference; PH; urine strip test; vitamin C

Concentration of vitamin C (mmol/L)	0.0	0.6	1.4	2.8	≥ 5.7
number of samples	24782	10257	3103	1642	1345

Concentration gradient		Concentration of vitamin C (mmol/L)		NO.	Difference
Concentration gradient		0.0	≥ 5.7	NO.	Difference
Glucose (GLU) (mmol/L)	0 (-)	±	-	39^* * Chi-square were performed, p-value < 0.05;	2
	2.8 (±)	±	±	3*	0
	5.6 (+)	+	-	15	2
	5.6 (+)	+	±	4	1
	14 (2 +)	2 +	-	9	3
	14 (2 +)	2 +	±	11	2
	14 (2 +)	2 +	+	14	1
	14 (2 +)	2 +	2 +	9	0
	28 (3 +)	3 +	2 +	15	1
	28 (3 +)	3 +	3 +	5	0
Total				74*	≥2
Total				54 *	<2
Ketone (KET) (mol/L)	0 (-)	±	-	4	2
	0.5 (±)	±	±	17	0
	1.5 (+)	+	+	3	0
	3.9 (2 +)	2 +	+	5	1
	3.9 (2 +)	2 +	2 +	2	0
	7.8 (3 +)	3 +	3 +	2	0
	7.8 (3 +)	4 +	4 +	2	0
Total				4^# # Chi-square were performed, p-value > 0.05.	≥ 2
Total				31^#	< 2
Protein (PRO) (g/L)	0 (-)	±	-	4	2
Protein (PRO) (g/L)	0.15 (±)	±	±	17	0
Total				4^#	≥ 2
Total				17^#	< 2
Leucocyte (WBC) (cells/μL)	0 (-)	±	-	23^#	2
	15(±)	±	±	53^#	0
	70 (+)	+	±	8	1
	70 (+)	+	+	6	0
	125 (2 +)	2 +	+	4	1
	125 (2 +)	2 +	2 +	11	0
	500 (3 +)	3 +	2 +	1	0
	500 (3 +)	3 +	3 +	17	0
Total				23^#	≥ 2
Total				100^#	< 2
Nitrite (NIT) (mg/dL)	negative (-)	positive	negative	6	2
Nitrite (NIT) (mg/dL)	positive (+)	positive	negative	9	0
Total				6^#	≥ 2
Total				9^#	< 2
Bilirubin (BIL) (μmol/L)	0 (-)	+	-	28	2
Bilirubin (BIL) (μmol/L)	17 (+)	+	+	5	0
Total				28*	≥ 2
Total				5*	< 2
Blood (BLD) (cells/μL)	0 (-)	±	-	39*	2
	15 (±)	±	±	11*	0
	25 (+)	+	-	21	2
	25 (+)	+	±	10	1
	80 (2 +)	2 +	±	6	2
	80 (2 +)	2 +	+	5	1
	200 (3 +)	3 +	+	3	2
	200 (3 +)	3 +	2 +	10	1
	200 (3 +)	3 +	3 +	13	0
Total				69*	≥ 2
Total				49*	< 2

Concentration gradient		Concentration of vitamin C (mmol/L)		NO.	Difference
Concentration gradient		0.0	2.8	NO.	Difference
GLU (mmol/L)	0 (-)	±	-	56^* * Chi-square were performed, p-value < 0.05;	2
	100 (±)	±	±	12*	0
	250 (+)	+	-	3	2
	250 (+)	+	±	14	1
	500 (2 +)	2 +	±	3	2
	500 (2 +)	2 +	+	3	1
	500 (2 +)	2 +	2 +	4	0
	2000 (3 +)	3 +	2 +	2	1
	2000 (3 +)	3 +	3 +	4	0
Total				62*	≥ 2
Total				39*	< 2
BIL (mg/dL)	0 (-)	+	-	3	2
BIL (mg/dL)	17 (±)	+	+	7	0
Total				3^# # Chi-square were performed, p-value > 0.05.	≥2
Total				7^#	<2
BLD (cells/μL)	0 (-)	±	-	51*	2
	10 (±)	±	±	12*	0
	25 (+)	+	+	1	0
	80 (2 +)	2 +	±	7	2
	200 (3 +)	2 +	+	13	1
	200 (3 +)	2 +	2 +	4	0
	200 (3 +)	3 +	3 +	4	0
Total				58*	≥ 2
Total				34*	< 2

Concentration gradient		Concentration of vitamin C (mmol/L)		NO.	Difference
Concentration gradient		0.0	1.4	NO.	Difference
GLU (mmol/L)	0 (-)	±	-	9	2
	2.8 (±)	±	±	12	0
	5.6 (+)	+	±	2	1
	5.6 (+)	+	+	3	0
Total				9^# # Chi-square were performed, p-value > 0.05.	≥ 2
Total				17^#	< 2
BLD (cells/μL)	0 (-)	±	-	9	2
BLD (cells/μL)	10 (±)	±	±	3	0
Total				9^* * Chi-square were performed, p-value < 0.05;	≥ 2
Total				3*	< 2

Concentration gradient		Concentration of vitamin C (mmol/L)		NO.	Difference
Concentration gradient		0.0	0.6	NO.	Difference
BLD (cells/μL)	0 (-)	±	-	15	2
BLD (cells/μL)	10 (±)	±	±	3	0
Total				15^* * Chi-square were performed, p-value < 0.05;	≥ 2
Total				3*	< 2

PH	the number of samples
	DIRUI dipsticks	SSA positive¹ 1 200 g/L SSA test was performed to confirm the result of protein;	SSA negative¹
	Positive results of protein		SSA negative¹
PH ≥ 8.0	520	56	464^* * Chi-square were performed, p-value < 0.05.
PH < 8.0	106	101	5*

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