Urine analyzer is an automatic instrument for determining certain chemical components in urine. It is an important tool for automatic urine inspection in medical laboratories. This instrument has the advantages of simple and fast operation. However, improper use of the urine analyzer and many intermediate links and influencing factors directly affect the accuracy of the automated analysis results, which will not only cause errors in the experimental results, but even delay the diagnosis. Therefore, the operator is required to be familiar with the principles, performance, and precautions of the automated instrument In order to make the results obtained by the urine analyzer more reliable and accurate, it is necessary to have a full understanding of the knowledge of the relevant aspects and influencing factors, and to use the automatic equipment correctly.
Detection Principles Of Urinalysis Devices
Urinalysis devices primarily operate on principles derived from chemistry, physics, biology, and microbiology.These principles guide the execution of the three main types of tests that the devices perform: physical tests, chemical analyses, and microscopic examinations.
Physical Tests
Physical tests evaluate the color and clarity of the urine sample, which can indicate certain conditions.For example, dark urine could suggest dehydration, while cloudy urine may point to an infection. The devices can measure these attributes using optical sensors.
Chemical Analyses
Chemical analyses are typically performed using a test strip or dipstick that changes color in response to various substances in the urine, including glucose, proteins, ketones, and pH, among others.Urinalysis devices detect these color changes using methods such as photometry or reflectance photometry.
The test strip is impregnated with specific reagents that react with the substances in the urine to produce color changes.The urinalysis device illuminates the test strip with a light source, and the reflected light is measured by an optical sensor.The intensity of the reflected light correlates with the concentration of the substance in the urine.
Microscopic Examinations
Microscopic examinations involve looking for cells, crystals, bacteria, and other microscopic particles in the urine that might indicate disease conditions.This process requires digital imaging technology, often enhanced with artificial intelligence.
Detection Methods Of Urinalysis Devices
Urine analyzers are of great value to the diagnosis, condition observation, prognosis evaluation and population health care of various diseases of the urinary system, digestive system, cardiovascular system and endocrine system. Using a urine analyzer for urine testing, the test results have the performance of accuracy, detection speed, and anti-cross-infection. The detection method of the urine analyzer is as follows:
1. Urine pH check
The results have two meanings: (1) reflect the state of 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, there is also monitoring of urine pH changes for other modules Interfering effect of zone response.
2. Urine specific density test
The former suspension method and refractometer method mainly measure the concentration of solids in urine. The 10-item urine analyzer makes the test strip method widely used. The acid-base indicator method was used. 1. The more acidic groups dissociated in the urine sample, the pH in the module changes. This change 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
According to the principle of indicator protein error, the membrane block mainly contains acid-base indicator jujube bromophenol blue, citric acid buffer system, etc. At pH 3.2, the anion produced by bromophenol undergoes a color change after combining with a cationic protein (albumin). The dry chemical method is simple and quick to measure urine protein, but attention should be paid to the occurrence of false positive and false negative results when using it. The sulfosalicylic acid method is recommended as a reference method for dry chemical detection of urinary protein.
4. Urinary Glucose Determination
The urine test strip method is mainly used to measure urine glucose by enzymatic method. The membrane block contains glucose oxidase, peroxidase and chromogen (potassium iodide as chromogen, positive reaction is red; o-methylbenzidine as chromogen, positive reaction is blue). The principle of determination is mainly as follows: glucose oxidase oxidizes glucose into glucuronic acid and hydrogen peroxide, and the latter is catalyzed by peroxidase to release the chromogen into color. When using the urine test strip method, it should be noted that the negative result of the urine test strip method may be inconsistent with the Benedictine method. In addition, the dry chemical method is more sensitive than the Benedictine method. At the same time, it should be noted that the reducing substances with strong affinity for oxygen in the urine can make the hydrogen peroxide produced by the dry chemical method reduce the color and make it a false negative. Test strips containing vitamin C oxidase can rule out this interference.
For the dynamic observation of diabetes, when dry chemistry shows positive results, it is best to use wet chemistry quantitative methods to ensure accurate urine glucose range or collect diurnal urine samples for urine glucose quantification.
5. Urine ketone test
The membrane blocks for detecting urine ketones mainly contain sodium nitrosoferricyanide, or react purple with acetoacetic acid and acetone in urine. It should be noted that the urine must be fresh and sent for inspection in time to avoid false negative results or low results due to the volatilization or decomposition of ketone bodies; there are differences in sensitivity between the dry method and the ketone body powder method; ketosis caused by different etiologies, ketone body The components are different, even if a patient has a different course of disease, there may be differences.
6. Urinary bilirubin, urobilinogen examination
The principle is that the conjugated bilirubin reacts with 2,4-dichloroaniline diazonium salt in a strongly acidic medium and turns purple. Main points to note: (1) Specimens must be fresh to prevent bilirubin from becoming biliverdin under sunlight; urobilinogen is oxidized into urobilin. (2) High concentrations of vitamin C and nitrite may make the results false negative. False positives may occur when large amounts of chlorpromazine are administered or metabolized in urine containing phenylazopyridine hydrochloride. (3) The excretion of urobilinogen in normal people fluctuates greatly every day, the amount is small at night and in the morning, and increases rapidly in the afternoon, reaching the peak at 2-4 in the afternoon; the clearance rate of urobilinogen is related to urine pH.
7. Urinary nitrite test
The membrane block mainly contains p-aminobenzene arsenic acid and 1,2,3,4-tetrahydroxy-p-quinoline-3 phenol. It is used to diagnose whether a patient is infected with Escherichia coli. Detection rate of nitrite in urine Whether the infected bacteria contain nitrate reductase, whether the food contains nitrate, and whether the urine sample stays in the bladder for 4 hours all affect the test results.
8. Urine white blood cell examination
The principle of detecting leukocytes in urine by urine test strip method is based on the fact that neutrophils contain specific esterases in the cytoplasm, which can act on indoxyl esters in membrane blocks, and react with diazonium salts to form purple condensation products. The depth is directly proportional to the number of neutrophils. The principle of white blood cell detection by urine analyzer is completely different from that of counting experiments under a microscope. The instrumental white blood cell test is only a screening test and cannot replace microscopic examination.
9. Urine hemoglobin, urine red blood cell examination
The film block mainly contains two substances: solanin hydroperoxide or cobalt hydroperoxide and chromogen (such as o-toluidine). The principle is that the hemoglobin in red blood cells in urine or the hemoglobin released from its destruction all have catalase-like activity, which can decompose solanin hydrogen peroxide or cobalt hydrogen peroxide, and the latter can oxidize related chromogens (such as o-toluidine) to make it color.
Conclusion
Understanding the principles and methodologies of urinalysis devices provides a foundation for appreciating their role in healthcare. These devices combine diverse fields-from biochemistry to data science-to deliver quick, reliable, and valuable insights about a patient’s health. With advancements in automation and artificial intelligence, the role of these devices is set to become even more pivotal in diagnostic medicine. While the science is complex, the outcome is clear: urinalysis devices are indispensable tools for modern healthcare.
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