1. urine pH test
The results have two meanings: ① reflect the acid-base metabolism in the body; ② Since the determination principle of urine protein and urine specific density is based on the color change of the last pH reagent on the module, the analysis of pH change can also monitor the interference of urine pH change on the reaction of other modules.
2. urine density test
The suspension method and refractometer method have been used to determine urinary specific density. With the advent of 10 urine analyzers, the test strip method has been widely used to determine urinary specific density. Its membrane block mainly contains polyelectrolytes (methyl ethyl enoic acid maleic anhydride), acid-base indicators and buffers. This is the acid brick indicator method, which was originally based on the principle that the change of PKA through polyelectrolytes is related to the concentration of urine ions. The polyelectrolyte in the hemp strip contains acid groups that dissociate with the high concentration in the urine sample. The more ions, the more dissociated ions of the acid groups, and the change of pH in the module can be displayed by the color change of the acid-base indicator in the membrane block, and then converted into the specific density of urine.
3. urine protein test
Urine protein determination of urine analyzer is based on the principle of indicator protein error. The membrane block mainly contains acid-base indicator jujube bromophenol blue, citric acid buffer system and active agent of EPI. At ph3.2, the anion produced by bromophenol changes color after binding with cationic protein (albumin). The dry chemical method is simple and fast to determine urinary protein, but it should be noted that: ① when patients take strong alkaline urine caused by quinine and sulfadiazine, false positive results will appear in the dry chemical method and false negative results will appear in the sulfosalicylic acid method Dilute acetic acid can be used to adjust the urine pH to 5-7 "and then conduct the test '' to distinguish whether the false positive is caused by strong alkaline urine ② Studies have proved that dozens of drugs can cause false positives in urine protein test. '' some scholars have detected urine protein in patients before and after administration of large doses of penicillin. '' the results show that: 2.5 million unit group for 2 hours \3.2 million unit group for 3 hours, 4.8 million unit group for 5 hours may produce false positives for sulfosalicylic acid method and false negatives for dry chemical method. ③ Different determination methods have different sensitivities to different kinds of proteins in the urine of patients. Biuret quantification can show sensitivity to albumin and globulin, while the sensitivity of globulin measured by dry chemistry is only 1/100-1/50 of albumin. Therefore, for nephrotic patients, especially those who need to systematically observe the urinary protein content in the course of disease development, the qualitative test with sulfosalicylic acid method (or heated acetic acid method) and the quantitative test with biuret method should be used. ④ False positive results may be caused when the specimen contains other secretions (such as reproductive system secretions) or contains more cellular components. It is suggested that sulfosalicylidene salicylate weight method should be used as a reference method for dry chemical detection of urinary protein.
4. urine glucose determination
Urine glucose was measured by enzyme method. The membrane contains glucose oxidase, peroxidase and chromogen. There are two main types of color sources used by different manufacturers: ① using potassium iodide as chromogen, the positive reaction is red; ② Using o-methylbenzidine as chromogen, the positive reaction was blue. The original quantity is that glucose oxidase oxidizes glucose into glucuronic acid and hydrogen peroxide, and the latter is released by peroxidase catalysis to make the chromogen color. This method is the most commonly used. Attention should be paid in the use of urine test strip method: ① the specificity of urine test strip method is different from that of Ban's qualitative method. The former has strong specificity and reacts with glucose; The latter reacts with non - original sugar and all reducing substances in urine, so the samples that are negative in urine test may be positive in Ban's method; ② The sensitivity of dry chemical method is different from that of Bancroft method. The sensitivity of dry chemical method is high. When the glucose content is 1.67-2.78mmol/l, the weak positive can appear; But the bancroftian method showed weak positive only at 8.33mmol/l; ③ The influence of interfering substances on the two methods is different: reducing substances with strong affinity for oxygen in urine can react with copper ions in Bancroft method to produce false positive, but it can make H2O2 produced by dry chemical method to reduce color and make it false negative. The elimination method is to boil the urine for a few minutes to destroy vitamin C before the experiment. At present, the test bands containing vitamin c oxidase can eliminate this interference. ④ The determination of urine glucose by dry chemical method is only a general semi quantitative test. Its designed concentration level is different from that of traditional Bancroft method, and the two can be compared with each other; Therefore, for the dynamic observation of diabetes, when there is a positive result in dry chemistry, it is best to use wet chemistry quantitative method to establish the accurate range of urine glucose or collect diurnal urine samples for urine glucose quantification.
5. urine ketone body examination
The membrane block of urine ketone body mainly contains sodium nitroso ferricyanide, or mainly reacts with acetoacetic acid and acetone in urine. Its sensitivity to acetoacetic acid is 50-100mg/l, while that to acetone is 400-700mg/l, which is not consistent with β- Hydroxybutyric acid reacts. Attention should be paid to in use: ① since acetone and acetoacetic acid in urine ketones are volatile, acetoacetic acid is easier to be decomposed into acetone by heating; After the urine is contaminated by bacteria, the ketone body disappears, so the urine must be fresh and sent for examination in time to avoid false negative results or low results due to the volatilization or decomposition of ketone bodies; ② The sensitivity of dry method and ketone powder method is different: the sensitivity of ketone powder method to acetoacetic acid and acetone is 80mg/l and 100mg/l respectively. It is not as sensitive as the test strip method, so the results of two methods on the same pathological specimen may be different, and special attention should be paid to the analysis of the results; ③ For ketosis caused by different causes, the composition of ketone body is different, even if a patient has different course of disease, for example, in the naming of early disease of diabetes ketoacidosis, the main ketone body components β Hydroxybutyric acid, with little or no acetoacetic acid, can lead to underestimation of the total ketone body. After the symptoms of diabetes ketoacidosis are relieved, β- The conversion of hydroxybutyric acid to acetoacetic acid makes the content of acetoacetic acid higher than that in the initial acute phase, which is easy to overestimate the condition. Therefore, the inspectors must pay attention to the development of the disease course and analyze the experimental results together with the clinicians.
6. examination of urinary bilirubin and urobilinogen
The principle of urine bilirubin determination is to combine bilirubin with 2,4-dichloroaniline diazonium salt in strong acid medium to produce purple red; The principle of urobilinogen determination is the same as that of the modified Ehrlich method. The main points for attention of the two methods are: ① the specimen must be fresh to prevent bilirubin from becoming biliverdin under sunlight; Urobilinogen is being oxidized to urobilin. ② When the urine contains high concentration of vitamin C and nitrite, the azo reaction is inhibited and the urine bilirubin is false negative. When a patient receives a large amount of chlorpromazine treatment or the metabolism of phenylazopyridine hydrochloride in urine, it can be false-positive. ③ Some endogenous substances in urine such as bilinogen, indole, bilirubin, etc. can make the test result of urinary bilinogen positive, and some drugs can also produce color to interfere with the test. ④ Urobilinogen excretion in normal people fluctuates greatly every day, with a small amount at night and in the morning, and increases rapidly in the afternoon, reaching the peak at 2-4 p.m; At the same time, the clearance rate of urobilinogen was correlated with urine pH. at pH5.0, the clearance rate was 2ml/min; It was increased to 25ml/min at ph8.0, so some scholars advocated that the patients should be given sodium carbonate in advance, and the alkalized urine should be collected slowly at 2-4 p.m. (2-hour excretion) for determination, so as to improve the detection rate.
7. urine nitrite test
The membrane block mainly contains p-aminophenylarsenic acid and 1,2,3,4-tetrahydroxy-p-quinoline-3 phenol. Most urinary tract infections are caused by Escherichia coli. Normal human urine contains nitrates from food or protein metabolism. When Escherichia coli infection proliferates in pool urine, nitrates are reduced to nitrites, which can diazonize p-ammonia-based phenylarsenate in the membrane block to form diazonium. The latter is coupled with 1,2,3,4-tetrahydroxy-p-phenylquinoline-3 whip to make the membrane block red, In order to diagnose whether the patient is infected by 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 contain nitrate reductase, whether the selected nitrate is contained in the food, and whether the urine sample stays in the bladder for more than 4 hours. If the above three conditions are met, the detection rate of this test is 80%, otherwise it can show negative results. Therefore, if the test is negative, the possibility of bacterial urine cannot be ruled out. If the sample nitrite test is positive, the urinary system infection cannot be fully confirmed. If the sample is placed too long or contaminated, it may be false positive. The correct judgment should be obtained through comprehensive analysis in combination with other urine analysis results.
8. urine leucocyte test
The principle of urinary leucocyte examination by urine test strip method is based on the fact that neutrophils contain specific esterase in the cytoplasm, which can act on indole phenol ester in the membrane block, and react with diazonium salt to form purple condensate. Its color is in direct proportion to the number of neutrophils. Attention should be paid to during operation: ① urine samples must be fresh, and they should be measured immediately after urine retention, so as to avoid the damage of leukocytes, which will lead to the experimental error between the dry chemical method and the microscopic method; ② This method can only detect neutrophils, but does not react with monocytes and lymphocytes. When rejection occurs in renal transplant patients, monocytes in urine mainly caused by lymphocytes or other causes will produce negative results; ③ When urine is contaminated with formaldehyde or contains high concentration of bilirubin or uses some drugs, Ji produces false positive; When urine protein >5g/l or urine contains red substances such as high-dose vancomycin, the results may be low or false. Since the principle of urine analyzer white blood cell detection is quite different from that of counting under the microscope, and its reporting method is also two different concepts, it is difficult to find out the corresponding relationship between the two. So far, there is no direct conversion method. Therefore, the instrument method white blood cell detection is only a screening test and cannot replace the microscope.
9. urine hemoglobin and urine red blood cell test
The film block mainly contains two substances, namely, solanesin hydrogen peroxide or cobaltene hydrogen peroxide and chromogen (such as o-methylbenzidine). The principle is that the hemoglobin in the red blood cells in urine or the hemoglobin released by its destruction has catalase like activity, which can decompose the solanesin hydroperoxide or cobalt hydroperoxide, and the latter can oxidize the relevant chromogen (such as o-methylbenzidine) to make it color. Attention should be paid to when using urine test strip method to check urine red: ① because the sensitivity of reagent strips from different manufacturers or different models is different, attention must be paid to the difference between batches when using; ② The dry chemical method can react with both intact red blood cells and free hemoglobin. Therefore, the clinical diagnosis and comprehensive analysis should be understood when reporting. Because the red blood cells in the final urine of nephrotic patients can be deformed and broken due to various factors, so that hemoglobin escapes, which can lead to the difference between instrumental method and water measurement method; ③ Urine containing thermophilic enzymes, myoglobin or bacteriuria can cause false positives; ④ A large amount of vitamin C may interfere with the test results, resulting in false negatives in some test bands, which should be vigilant