Hematuria is an increase in urine red blood cells. Positive urine occult blood (occult blood) is a manifestation of hematuria. Hematuria can be positive for urine occult blood (occult blood), but positive urine occult blood (occult blood) does not necessarily mean hematuria. A positive urine occult blood (occult blood) is medically called a positive urine benzidine test. Because the red blood cells in urine contain hemoglobin, the ferrous hemoglobin in hemoglobin has peroxidase-like activity, which can cause the decomposition of peroxide to release reactive oxygen species, and the oxidized substrate o-toluidine becomes o-benzidine, and a color change occurs: from yellow to grass green, or even dark blue, that is, a positive urine benzidine test. There are many reasons for a positive urine occult blood (occult blood) test. In addition to hematuria, there are also many other causes of positive urine occult blood (occult blood) test that are not hematuria: 1. hemoglobinuria. 2. 2. myoglobinuria. 3. Bacteriuria (production of oxidizing substances by bacteria). 4, Urine contains oxidizing substances (hypochlorite, etc.). 5, urine contains some kind of enzyme that can make peroxide decomposition. 6, Stale urine, high temperature storage, low tension urine (red blood cell destruction). 7, Expired urine test strips, deterioration, over-sensitive urine analyzer, etc. Therefore, hematuria can be positive for urinary occult blood or urinary occult blood, but positive urinary occult blood or urinary occult blood is not necessarily hematuria. The two cannot be equated.