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Urine Analyzer Test Method
- Sep 04, 2018 -

1, urine PH check

The results have two meanings: 1 reflects the acid-base metabolism in the body; 2 because the urine protein, urine specific density measurement principle is based on the color change of the final PH reagent on the membrane, so the analysis of PH changes and monitoring of urine pH changes to other membranes The interference effect of the reclamation reaction.


2, urine specific inspection

The urine specific density measurement has been carried out by suspension method and refractometer method. The main determination of the concentration of solids in urine with the advent of 10 urine analyzers, the test strip method for the determination of urine specific density is widely used, and the membrane block mainly contains multimerization. The electrolyte (methylene methacrylate), the acid-base indicator and the buffer, which is based on the acid tile indicator method, is based on the principle that the Pka changes through the polyelectrolyte and the urine ion concentration. The polyelectrolyte in the anesthetic strip contains an acidic group which is dissociated from the large concentration in the urine sample. The more ions, the more the acidic group decomposes the ions, and the pH in the membrane is changed. The color change of the acid-base indicator in the block is displayed and converted to the specific density of the urine.


3, urine protein examination

The urine analyzer urine protein measurement is based on the principle of indicator protein error. The membrane block mainly contains the acid-base indicator jujube bromophenol blue, the citric acid buffer system and the active agent of the table. At pH 3.2, the anion produced by bromophenol undergoes a color change when combined with a cationic protein (albumin). The dry chemical method for the determination of urinary protein is simple and rapid, but it should be noted that: 1 patients taking strong alkaline urine caused by drugs such as quinine and sulfadiazine will cause false positive results in dry chemical methods and sulfosalicylic acid. The method results in a false negative result. You can use the dilute acetic acid to adjust the pH of the urine to 5-7'' and then experiment '' to distinguish whether it is false positive due to strong alkaline urine. 2 Research proves that dozens of drugs can check urine protein There was a false positive ''A scholar has tested the urine protein before and after administration of large doses of penicillin''. The results showed that: 2.5 million units of the infusion, 2 hours, 3.2 million units, 3 hours, 4.8 million units, 5 hours. A false positive for the sulfosalicylic acid method and a false negative for the dry chemical method. 3 Different methods of measurement are sensitive to the detection of different kinds of proteins in the urine of patients. Biuret quantification can be sensitive to albumin and globulin, while the sensitivity of dry chemical measurement of globulin is only 1/ of albumin. 100-1/50. Therefore, in patients with kidney disease, especially in the case of disease development, it is necessary to systematically observe the urine protein content in the quantitative test using the sulfosalicylic acid method (or heated acetic acid method) qualitative and biuret method. 4 specimens containing other secretions (such as reproductive system secretions) or contain more cellular components, can cause false positives. The sulfo-perpendylation method is recommended as a reference method for the detection of urinary protein by dry chemistry.


4, urine glucose determination

The urine test method for the determination of urinary glucose is by enzymatic method. The membrane block contains glucose oxidase, peroxidase and chromogen. There are two main types of color sources used by different manufacturers: 1 using potassium iodide as a chromogen, and the positive reaction is red; 2 using o-methylbenzidine as a chromogen, and the positive reaction is blue. The measured amount is that glucose oxidase oxidizes glucose to glucuronic acid and hydrogen peroxide, which is then catalyzed by peroxidase, which causes the chromogen to be colored, and is most commonly used in such a manner. The urine test strip method should be noted in use: 1 the specificity of the urine test strip method and the Ban's qualitative method is different, the former has strong specificity, and the glucose reacts with glucose; while the latter reacts with the urine and has all the reducing sugar and all reducing properties. The substances all react, so the specimens that are negative in the urine test method may have positive results in the Ban's method; 2 the sensitivity of the dry chemical method and the Ban's method is different, the sensitivity of the dry chemical method is high, and the glucose content is 1.67-2.78 mmol. A weak positive can occur at /L; the Ban's method is 8.33mmol/L, which is weakly positive; 3 Interfering substances have different effects on the two methods: the urine contains a reducing substance with a strong affinity for oxygen and the Ban's method. The action of copper ions in the process produces a false positive, but it can reduce the coloration of H2O2 produced by the dry chemical test strip to make it a false negative. The method of elimination is to first boil the urine for a few minutes to destroy the vitamin C and then carry out the experiment. A test strip containing vitamin C oxidase is now available to rule out this interference. 4 Dry chemical method for the determination of urinary glucose is only a general semi-quantitative test, and its designed concentration level is different from that of traditional Ban's. The two are comparable to each other; therefore, for the dynamic observation of diabetes, positive results appear in dry chemistry. Preferably, wet chemical quantification is used to establish an accurate range of urinary glucose or to collect diurnal urine samples for urine glucose quantitation.


5, urine ketone body examination

The membrane for detecting the urinary ketone body mainly contains sodium nitroferrocyanide or reacts with acetoacetic acid or acetone in the urine. It has a sensitivity to acetoacetate of 50-100 mg/L and 400-700 mg/L for acetone, and does not react with β-hydroxybutyric acid. Note in use: 1 Because both acetone and acetoacetate in the ketone body are volatile, acylacetic acid is more susceptible to heat to form acetone; after the urine is contaminated by bacteria, the ketone body disappears, so the urine must be fresh and promptly sent for inspection. In order to avoid false negative results or low results due to volatilization or decomposition of ketone bodies; 2 sensitivity between dry method and ketone body powder method: ketone body powder method sensitivity to acetoacetic acid and acetone are 80mg / L and 100mg / L. It is not as sensitive as the test strip method, so the difference between the two methods of the same pathological specimen may result in the results. Special attention should be paid to the results of the analysis; 3 the ketosis caused by different causes, the composition of the ketone body is different, even if the patient has different disease course, there may be differences. For example, in the early name of diabetic ketoacidosis, the main ketone component, β-hydroxybutyric acid, has little or no acetoacetic acid, and the results measured at this time may lead to an underestimation of the total ketone body. After the symptoms of diabetic ketoacidosis are alleviated, β-hydroxybutyrate is converted to acetoacetate, which in turn makes the acetoacetate content higher than the initial acute phase, which is easy to overestimate the condition. Therefore, the inspector must pay attention to the development of the disease and analyze the experimental results together with the clinician.


6, urinary bilirubin, urinary biliary examination

The principle of urinary bilirubin is combined with bilirubin in a strong acidic medium, and the coupling reaction with 2,4-dichloroaniline diazonium salt is purple-red; the principle of measuring urobilinogen is the same as the modified Ehrlich method. The main points of attention of the two methods are: 1 The specimen must be fresh to prevent bilirubin from becoming biliverdin under sunlight; urinary biliary is oxidized to urobilin. 2 When urine contains high concentrations of vitamin C and nitrite, inhibition of azo reaction makes urinary bilirubin a false negative. When the patient receives a large amount of chlorpromazine treatment or the metabolism of phenylazopyridine hydrochloride in the urine, it can be false positive. 3 Some endogenous substances in the urine, such as porphobilinogen, sputum, bilirubin, etc., can cause urinary biliary examination results to be positive, and some drugs can also produce color interference experiments. 4 Normal urinary biliary excretion fluctuates greatly every day, with little night and morning, and increases rapidly in the afternoon, reaching the highest peak at 2-4 pm; while the clearance rate of urinary bile is related to urine PH, PH5.0 The clearance rate is 2ml/min; when it is Ph8.0, it is increased to 25ml/min. Therefore, some scholars advocate pre-administering patients to take sodium bicarbonate to alkalinize urine and slow urine collection at 2-4 o'clock in the afternoon (2 hours discharge) The measurement is performed to increase the detection rate.


7, urine nitrite check

The membrane block mainly contains p-aminophenyl arsenate and 1,2,3,4-tetrahydroxy-p-quinolin-3-ol. Most of the urinary tract infections are caused by Escherichia coli. Normal urine contains nitrates derived from food or protein metabolism. When Escherichia coli infection occurs in the urine, the nitrates are reduced to nitrous acid. Salt, which can diazotize ammonia basal benzene arsenate into a diazonium salt, and the latter is coupled with 1,2,3,4-tetrahydroxy-p-quinoline-3 whip to cause the film to produce red color. In order to diagnose whether the patient is infected with Escherichia coli, the detection sensitivity is 0.03-0.06g/l. The detection rate of nitrite in urine is affected by whether the infected bacteria contains nitrate reductase, whether the food contains the selected nitrate or whether the urine sample stays in the bladder for more than 4 hours, which meets the above three conditions. The detection rate of the test was 80%, and vice versa. Therefore, the negative test of this test can not rule out the possibility of bacterial urine. The positive nitrite test can not completely confirm the urinary system infection. The specimen is placed too long or the pollution can be false positive. It should be combined with other urine analysis results. The correct judgment.


8, urine white blood cell examination

The principle of urine test for the detection of white blood cells in the urine is based on the cytoplasmic cytoplasm containing specific esterase, which can act on the indophenol ester in the membrane block, and react with the diazonium salt to form a purple condensate. The depth is proportional to the number of neutrophils. Should pay attention to the operation: 1 urine specimens must be fresh, should be measured immediately after the urine, so as not to break the white blood cells, leading to artificial chemical and microscopic examination of artificial errors; 2 this method can only measure neutrophils, not with Mononuclear cells, lymphocyte reaction, when a renal transplant patient has a rejection reaction, the urine in the urine caused by lymphocyte-based or other causes of mononuclear cells will produce negative results; 3 urine contaminated with formaldehyde or contains High concentrations of bilirubin or the use of certain drugs, Kyrgyzstan produces false positives; urine protein > 5g / L or urine containing large doses of cephalosporin and other red matter, the results may be low or false results. Because the white blood cell detection of urine analyzer is completely different from the principle of microscopic counting experiment, its reporting method is also two different concepts. It is difficult to find the corresponding relationship between the two. So far there is no direct conversion method, so the instrument method white blood cell The examination is just a screening test and must not be replaced by a microscopic examination.


9, urinary hemoglobin, urinary red blood cell examination

The membrane block mainly contains hydrogen peroxide, solanin or hydrogen peroxide, and chromogen (such as o-benzidine). The principle is that the hemoglobin in the red blood cells in the urine or the hemoglobin released by the destruction has catalase-like activity, which can decompose the hydrogen peroxide or the hydrogen peroxide, which can oxidize the relevant chromogen. (such as o-benzidine) to make it color. Urine test strip method should be paid attention to when checking the intra-urinary red operation: 1Because different manufacturers or different types of reagents have different sensitivity, it is necessary to pay attention to the difference between batches; 2 dry chemical method can be combined with intact red blood cells. Free hemoglobin response, so report on the clinical diagnosis, comprehensive analysis. Because the red blood cells in the final urine of patients with nephropathy can be deformed by various factors to cause hemoglobin to escape, the difference between the instrument method and the water method can be caused; 3 the thermophilic enzyme, myoglobin or bacteriurea contained in the urine can cause false positives. ; 4 large amounts of vitamin C can interfere with the test results, so that some test strips produce false negatives, should be vigilant