In the pediatric nephrology department, we often encounter children’s parents with the urine routine list, asking the doctor urine routine in the latent blood and red blood cells problem. How are the occult blood and red blood cells in the urine routine laboratory tested? Today we share a little knowledge with you, so that we can learn and progress together. First of all, talk about the urine analyzer occult blood reaction principle: hemoglobin (Hb) peroxidase-like activity of methaemoglobin can make peroxide decomposition to release the new ecological [O], the latter oxidation substrate o-toluidine into o-benzylamine occurs by the yellow ¡ú grass-green ¡ú dark blue color change. Urine microscopy is through the magnifying effect of the microscope directly to the cells and other formed components of the intuitively real in the mirror, is a true reflection of the substrate. Gao Xuguang, Department of Pediatrics, The First Affiliated Hospital of Henan College of Traditional Chinese Medicine Urine analyzer to detect urinary occult blood, in the mixing of 10ml of fresh urine immersed in urine test strips 1s and then removed, on the instrument for the determination of the automatic printing results. The result report is divided into: -, ±, +, ++, +++, ++++, ++++. Microscopic examination: take 10ml of urine in a test tube, centrifuge it at 1500r/min for 5min, discard the supernatant and leave 0.2ml of precipitate. mix it well, take out about 20μl on a slide, add a coverslip (2.0cm×2.0cm), then observe the whole picture with low magnification using a weaker light, so as not to miss a small amount of meaningful objects, and then identify the cells with a high magnification lens. The result is reported as: х cells/high-power field of view (HP). How to count if there are several plus signs on the laboratory test, it is simple 1 plus sign is equal to 10 red blood cells. False-positive: that is, the urine analyzer occult blood reaction is positive, microscopy negative, that is, no red blood cells microscopy, the common reasons are: (1) hemoglobin (Hb): urine analyzer occult blood reaction can be positive with both intact RBCs, but also can be positive with the release of Hb from the dissolution of the RBCs, and the microscope can only be detected in the urine of the RBCs are not dissolved. the amount of Hb in the urine of a healthy person is very small, the qualitatively negative. In healthy individuals, the amount of Hb in the urine is minimal and is characterized as negative. In disease, there are two sources of urinary Hb: one is the occurrence of intravascular hemolysis, in which plasma Hb exceeds the binding capacity of bound bead proteins and free Hb is excreted from the urine. The other is bleeding in the urinary tract (especially the upper urinary tract), where RBCs destroy Hb escaping at hypertonicity or (and) hypotonicity. In this case, the urine analyzer has a positive occult blood reaction, but the RBCs are not seen on microscopic examination of the urine sediment or only fragments of RBCs are seen. (2) Myoglobin (Mb): the molecule also contains heme groups, with peroxidase activity. Mb is mainly found in cardiac and skeletal muscle tissues, the content of normal human urine is very small, can not be detected. When the myocardium or skeletal muscle serious injury, plasma Mb increases, the renal excretion, so that the urine Mb content increases, so the occult blood reaction is positive, microscopic examination of RBC is negative. (3) Certain patients’ urine contains enzymes that are unstable to heat, which can also cause the reagent block to change color, resulting in a positive occult blood reaction and a negative microscopic examination. (4) Certain oxidizing pollutants, such as hypochlorite, can cause false-positive occult blood reactions. (5) Bacteriophageal urine: urine is a good culture medium for bacteria, and some bacteria will produce oxidizing substances in bacteriophageal urine, which will change the color of the reagent block, resulting in a positive occult blood reaction and a negative RBC microscopic examination. In addition, the invasion of microbial peroxidase can also cause false positives. (6) Prolonged storage and high temperature experiments have proved that specimens that are not fresh, stored for a long time or stored at high temperatures increase the positive rate of occult blood reaction, while RBC microscopy decreases accordingly, and false-positive test results are very likely to occur. Therefore, it is recommended that urine specimens should not be stored for more than 4 hours. (7) False-positive test results can be caused by overdue or contaminated urine test strips as well as improper storage and incorrect operation methods. (8) urine analyzer sensitivity is too high (0.2mg / dl appears + +), “level difference” range is too large (0.8 ~ 50mg / dl level for + + +), often encountered in the instrument test for + +, while the microscopic test of red blood cells is negative, and clinically can not find any cause of hemoglobinuria. (9) Influence of food or drugs: When the urine is alkaline due to diet or drugs, RBCs dissolve and break down, forming brown particles, and the latent blood reaction is positive while the microscopic test is negative. By analyzing the above nine reasons, if there is a urine routine simple occult blood with a plus sign, whether there is a kidney problem, whether there are red blood cells in the urine is to be asked, only as a reference in the clinic. If there are red blood cells on microscopic examination, further examination is needed to determine the source of the red blood cells. False negative: that is, positive microscopy, that is, there are red blood cells in the urine microscopy, but the urine analyzer occult blood reaction is negative, and its common causes are: (1) VitC When a large number of exist in the urine, it can compete to seize the oxygen produced by the reaction, causing a false-negative reaction. (2) high specific gravity, high protein urine samples to reduce the sensitivity of the reagent block occult blood reaction, so that the occult blood reaction appears false negative. (3) Increased mucus content in the urine causes the RBCs to be encapsulated and the reagent cannot contact the Hb, which makes the occult blood reaction false negative. There is no occult blood in the urine routine, and the presence of the above three conditions, occult blood negative is also to be a question mark. Urine analyzer method of detecting red blood cells in the urine is exceptionally sensitive, sometimes there are differences with the results of microscopy, to fully consider the factors affecting the results, and combined with the clinical analysis, in principle, the urine analyzer occult blood reaction of the positive results should be retested by microscopy, which is an important part of the quality assurance of urine testing and the key to do a good job. For the urine analyzer method of determination of negative results and microscopic inconsistency should also be reviewed to ensure the accuracy and reliability of the results. This is one of the reasons that when you come to the pediatric nephrology ward, the doctor makes repeated urine routine checks. In addition, it is pointed out that so far, no instrument’s results can completely replace microscopy, and urine sediment microscopy is still an indispensable means of examination in urinalysis with its unique clinical value. In our pediatric nephrology laboratory urine sediment microscopy is a mandatory part of the experiment, so outpatient review of children, parents are always asked to send urine to the sixth floor pediatric laboratory. Therefore, it is recommended that children with renal disease should be sent to the laboratory with microscopic conditions for routine urine examination.