NMP22, also known as urinary nuclear matrix protein 22, is a screening indicator for bladder cancer and may be elevated in patients with hematuria or suspected bladder cancer, but it is not the only basis for the diagnosis of bladder cancer. However, it is not the only basis for the diagnosis of bladder cancer. Patients with long-term smoking or long-term exposure to paint and chemical products may also have elevated NMP22, so elevated NMP22 is not a specific sign of tumor and further urological CT, cystoscopy or biopsy is needed to confirm the diagnosis of cancer. The most reliable basis for confirming the presence of tumor is biopsy and pathology biopsy in order to achieve 100% diagnosis. Some hematologic tumor indicators that are elevated only serve as a screening test and further tests are needed to confirm the diagnosis. Therefore, a positive urinary matrix protein 22 cannot confirm the diagnosis of cancer, but needs to be combined with the patient’s symptoms and other tests to confirm. Urine matrix protein 22 is also found in special groups, such as patients who smoke and have long-term exposure to chemical products, but do not have cancer.