Precision Diagnosis and Blood Glucose Monitoring in Diabetes: From Multidimensional Laboratory Testing to a Guide to Choosing Self-Monitoring Devices

IV. Simple Methods for Diagnosing Diabetes How can patients determine if they have diabetes? Generally, when patients experience obvious typical or atypical symptoms of diabetes, they will consider the possibility of having diabetes. However, symptoms such as thirst, excessive drinking, and frequent urination alone cannot diagnose diabetes, as the diagnosis of diabetes is based on blood glucose levels. Furthermore, a positive urine glucose test is not a diagnostic criterion for diabetes, as a plus sign (+) in urine glucose can sometimes occur in normal individuals. Therefore, a diagnosis of diabetes must be based on the blood glucose concentration obtained from a venous blood sample. The American Diabetes Association (ADA) updated its diagnostic criteria for diabetes in 1997. Simply put, if blood glucose levels meet either of the following two criteria, diabetes can be diagnosed: Fasting blood glucose > 7.0 mmol/L, or 2-hour postprandial blood glucose > 11.1 mmol/L. Ideally, the 2-hour postprandial blood glucose level should be determined using a 75-gram oral glucose tolerance test (OGTT), but currently, the standard is often based on the intake of two steamed buns, which can affect the accuracy of the blood glucose reading.

V. Laboratory Tests for Diabetes (I) Urine Glucose Measurement In normal individuals, the amount of glucose excreted in urine daily does not exceed 100 mg, and routine urine glucose qualitative tests generally cannot detect it. If the amount of glucose excreted in urine daily exceeds 100 mg, it is called glycosuria. (II) Blood Glucose Measurement Currently, the glucose oxidase method is mostly used, and the o-toluidine method is also used. The normal fasting blood glucose is 3.9-6.1 mmol/L. If two repeated measurements of fasting blood glucose are ≥7.8 mmol/L, diabetes can be diagnosed. (III) Glucose Tolerance Test The glucose tolerance test includes: (1) Oral glucose tolerance test (OGTT); (2) Intravenous glucose tolerance test (IGTT); (3) Cortisone glucose tolerance test. (IV) Insulin Measurement Measurement Standards: (1) The normal reference value for fasting is 5-25 mIU/L. For insulin-dependent individuals, it is below the lower limit of normal or undetectable. For non-insulin-dependent individuals, it is within the normal range or higher than normal. (2) Insulin release test: Insulin-dependent type has no peak and a flat curve; Non-insulin-dependent type has a lower peak or a delayed peak than normal. (V) C-peptide assay (1) The normal value in fasting blood is 1.0±0.23 μg/L. Insulin-dependent type is reduced or undetectable, while non-insulin-dependent type may be within the normal range or slightly lower. (2) C-peptide release test curve is the same as insulin release test curve.

VI. Blood Glucose Self-Monitoring (I) Advantages of Blood Glucose Testing More and more patients are now using blood glucose monitors as the main means of blood glucose monitoring. Blood glucose testing has the following advantages. (1) Blood glucose testing is not affected by changes in the renal glucose threshold and is more accurate than urine glucose testing. (2) Blood glucose testing is mostly a fully quantitative method, so it can more accurately reflect the actual blood glucose status of the body. (3) Blood glucose testing can not only reflect hyperglycemia, but also hypoglycemia, so it is more suitable for patients injecting insulin to detect hypoglycemia in time. It is also suitable for patients taking oral hypoglycemic drugs, so that medication and dosage can be adjusted in time to avoid blindness. (II) Methods of Blood Glucose Testing There are two main methods of blood glucose testing: test strip method and blood glucose monitor. At present, there are various blood glucose monitors and test strips for sale in the domestic market. The testing principles are basically the same. Patients can consult doctors or diabetes specialist nurses on how to choose. (1) Colorimetric test strip method: This method does not require a blood glucose monitor and is relatively inexpensive. The disadvantage is that it is still a semi-quantitative testing method. A soft film is attached to one end of the test strip, which is usually marked with a more conspicuous color. There are chemical reagents on the film. When it comes into contact with sugar, it will react chemically and change color. (2) Blood glucose monitor method: Similar to the colorimetric method, blood glucose monitors also require blood glucose test strips, and some types of test strips are also labeled with colorimetric plates on their packaging, so the colorimetric method can be used even without a blood glucose monitor. However, if a blood glucose monitor is used, the capillary blood glucose measured is more accurate. Early blood glucose monitors were cumbersome to operate, requiring the blood on the test strip to be wiped off before inserting it into the machine for colorimetric comparison, which not only easily contaminated the machine but also had a large error, and have now been gradually phased out; the new generation of blood glucose monitors is not only easy to operate but also requires much less time, so they are increasingly accepted by patients. (III) Precautions for purchasing a blood glucose monitor Before purchasing a blood glucose monitor, you must pay attention to the following aspects. (1) Choose a blood glucose monitor with good after-sales service and a guaranteed long-term supply of test strips, because the test strips of different brands of blood glucose monitors are different and cannot be borrowed from each other. (2) Choose a blood glucose monitor that is easy to operate. When purchasing, ask the salesperson to demonstrate for you and confirm that you can operate it independently. (3) The numbers displayed on the screen of the blood glucose monitor should be easy to read. (4) If you have poor eyesight, you should choose a blood glucose meter that can report the measured value with sound. (5) It is best to choose a blood glucose monitor with a "memory" function so that you can store your measured blood glucose value. (IV) General steps for measuring blood glucose (1) Wash your hands with soap and water and dry them, or disinfect them with alcohol and let them air dry. (2) Use a lancet to collect blood. (3) Put a drop of blood on the test film of the test strip.