Test strips for the determination of urea In blood, serum and plasma

Principle

The test strip contains a reaction zone and an indicator zone with a scale. In the reaction zone, urea is specifically splitted into carbon dioxide and ammonia by urease. After diffusion through the gas phase, ammonia colours part of the pH indicator blue. The length of the blue zone depends on

Urea concentration – temperature – reaction time

The temperature and the reaction time are constant so that the length of the blue zone indicates the urea concentraiton directly.
Storage instructions for the test strips
The test strips can be used up to the expiry date if stored in a closed container below 30 °C.
Warnings and precautions
Take note of the necessary precautions for the handling with specimen.
Test strip preparation
The test strips are ready to use.
Specimen
Capillary blood, full blood, serum and plasma (heparin, oxalate and citrate are suitable for obtaining plasma while EDTAand fluoride are not suitable).
Discard contaminated specimens!

Assay procedure

 

Application of the samples

 

*When capillary blood is used , ensure that the reaction zone is completely saturated.

Assessment

Emergency diagnosis

For rough estim ation of the urea concen tration in full blood, the length of the blue zone can be read afte r only 5 min. Lengths of 10 mm or more indicate concentra tions of over 300 mg/dl (50 mmol/L) of urea equivalent to 140 mg/dl of urea-N.

Normal method 30 min, approx. 22°c*

Serum, Plasma					Full blood
Blue zone	Urea			Urea-N	Blue zone	Urea			Urea-N
mm	mg/dL	I	mmol/l	mg/dL	mm	mg/dL	I	mmol/l	mg/dL
0	14	2		7	0	17	3		8
0.5	17	3		8	0.5	21	4		10
1	19	3		9	1	25	4		12
1.5	22	4		10	1.5	29	5		14
2	25	4		12	2	33	6		15
2.5	28	5		13	2.5	38	6		18
3	31	5		14	3	42	7		20
3.5	34	6		16	3.5	46	8		22
4	37	6		17	4	50	8		23
4.5	41	7		19	4.5	54	9		25
5	44	7		20	5	58	10		27
5.5	48	8		22	5.5	63	10		29
6	51	8		24	6	67	11		31
6.5	55	9		26	6.5	71	12		33
7	59	10		28	7	75	13		35
7.5	62	10		29	7.5	79	13		37
8	66	11		3 1	8	83	14		39
8.5	70	12		33	8.5	88	15		41
9	73	12		34	9	92	15		43
9.5	77	13		36	9.5	96	16		45
10	80	13		37	10	100	17		47
10.5	84	14		40	10.5	104	17		49
11	88	15		41	11	108	18		50
11.5	91	15		42	11.5	113	19		53
12	95	16		44	12	117	20		55
12.5	99	16		46	12.5	121	20		56
13	102	17		48	13	125	21		58
13.5	106	18		50	13.5	129	21		60
14	109	18		51	14	133	22		62
14.5	113	19		53	14.5	138	23		64
15	117	19		55	15	142	24		66
15.5	120	20		56	15.5	146	24		68
16	124	21		58	16	150	25		70
16.5	128	21		60	16.5	154	26		72
17	131	22		61	17	158	26		74
17.5	135	22		63	17.5	163	27		76
18	138	23		64	18	167	28		78
18.5	142	24		66	18.5	171	28		80
19	146	24		68	19	175	29		82
19.5	149	25		70	19.5	179	30		84
20	153	25		72	20	183	30		86
20.5	157	26		73	20.5	188	31		88
21	160	27		75	21	192	32		90
21.5	164	27		77	21.5	196	33		92
22	167	28		78	22	200	33		94
22.5	171	28		80	22.5	204	34		95
23	175	29		82	23	208	35		97
23.5	178	29		83	23.5	213	36		100
24	182	30		85	24	217	36		101
24.5	186	31		87	24.5	221	37		103

*Temperature correction factor

Tempreture (oc)	14	16	18	20	25	27	29	31
Factor	1.2	1.15	1.1	1.05	0.95	0.9	0.85	0.8

 

Dilution limit

If the concentration exceeds the measuring range, the sample mater ial can be diluted 1 + 2 with distilled water. The va lues obtained f rom the conversion table (norma l method ) must then be multip lied by 3.

Reference range

	Urea		Urea-N
	mg/dl	mmol/l	mg/dl
Serum	20 – 40	3.3 – 6.7	10 – 20
Full blood	18 – 36	3.0 – 6.0	9 – 18

Protein intake	Normal range urea (serum)
g/kg body weight and day	mg/dl	mmol/L
0.5	13 – 23	2.2 – 3.8
1.5	24 – 52	4.0 – 8.7
2.5	31 – 59	5.2 – 9.8

 

Literature

• 1. Richtarich R, Colombo JP. In: Karger S, Klinischa Chemie. 4th edition. Basal: 1978,p.323
• 2. F. Dunsbach , Seiffert UB. PrOfung von Merckognost Hamstoff unter Routinebedingungen. Med. Lab. 1974; 11: p. 263-65.
• 3. Appel W. Medizin 3, 1975; 9: p. 778 – 779

Performance characteristics

Measuring range

The test has been deve loped to determine Urea concentrations up to 180 mg/dL. When values exceed this range samples should be diluted 1+2 with distilled water and the result multiplied by 3.

Specificity

Because of the reaction principle the test is specific for urea.

Limit of detection

The lower limit of detection is 14 mg/dL.

Precision

 

Intra assay n = 20	Mean [mg/dl]	SD [mg/dl]	CV [%]
Sample 1	24	2.22	9.39
Sample 2	83	3.22	3.87
Sample 3	127	3.04	2.39

 

Intra assay n = 20	Mean [mg/dl]	SD [mg/dl]	CV [%]
Sample 1	24	1.49	6.31
Sample 2	82	3.01	3.69
Sample 3	130	3.76	2.90

 

Method comparison

A comparison between DiaSys Urea Test strips (y) and the GLDH method (x) using 222 samples gave following results: y = 1.00 x + 2.61 mg/dL; r = 0.981.

Waste management

Please refer to the local legal requirements.

Manufacturer

DiaSys Diagnostic Systems GmbH
Alta Strassa 9 65558 Holzheim Garmany

Evaluation

Scale divisions of the indicator zone: Millimeters with thicke r lines for 0, 5.10, 15, 20 mm. The bottom thick line indicates the zero line. Reading off:Read the transition from blue to yellow at the bottom of the meniscus (arrow in fig. 3).