Occult blood is occult blood, so urinary occult blood is urinary occult blood. Urine occult blood alone cannot be used as a basis for diagnosing disease, because normal people may also have urine occult blood under normal circumstances, only that normal urine occult blood is negative. Normal urine contains very few blood red blood cells, so urine occult blood is negative. Positive urine occult blood is the result of a routine urine test, which indicates that the blood red blood cells in the urine have reached a certain number. First of all, let’s understand the principle of urine occult blood test, if there are red blood cells in the urine, one of the hemoglobin in the red blood cells is ferrous hemoglobin, which has weak peroxidase activity and can make the oxide in the urine test paper (such as peroxyanisole) release new ecological oxygen, which in turn can oxidize the test paper with o-toluidine to blue. The instrument then determines whether or not the urine is positive for occult blood or the degree of positivity based on the shade of this coloring, and thus presumes that red blood cells may be present in the urine. The use of urine occult blood test to determine the presence of hematuria is mainly intended to be convenient and quick, and is suitable for outpatient screening of hematuria. If vitamin C is used clinically, it will be excreted from the urine in large amounts, which neutralizes the oxides in the urine test paper and cannot produce oxygen, causing a false negative reaction. And when the urinary tract infection, certain bacteria can produce peroxidase, causing a false positive; some crystals can also affect the occult blood measurement, causing a false positive result; some trauma or tissue infection can cause the urine to contain myoglobin will also make the urine occult blood positive. In addition, urine occult blood test is also subject to some external factors such as whether the specimen is fresh, whether the reaction time is appropriate, whether the test strips are expired or contaminated, etc., which can cause false positive or false negative results of urine occult blood test. However, whether there are really red blood cells in the urine mainly relies on the retention of urine, centrifugation to take the sediment to determine with microscopic observation. The diagnosis of hematuria cannot be based on urine occult blood alone, but mainly on microscopic examination of urine sediment. Therefore, when your child has positive occult blood in urine, parents should not be anxious, and further examination is needed to determine whether it is hematuria, do not think that the so-called kidney “inflammation” because of positive occult blood in urine and blindly seek medical advice and medication.