From an inspection perspective, the linear range of the reagent!
A linearity test is an experiment that measures the detection range of a method. Through the linear test, the highest and lowest detection values of the method can be known, and the detection range of the method can be determined to prevent detection errors of samples with too low or too high contents.
The concentration and absorbance of a substance within the linear range should be directly proportional and consistent with Beer's law. Therefore, the measured results within this range should be reliable. Results beyond the upper and lower limits are unreliable. In order to make the results reliable, the In this case, the sample dosage should be increased or the sample should be diluted and tested again.
The linear test method is basically the same as the preparation of the standard curve. High-concentration samples are made into 10 stages of dilutions, and each portion is measured twice to confirm the possible range of high-concentration measurement. The difference is that the concentration range of the series of standard solutions is wider and the number of measured standard tubes is large. Generally, a linear test is performed first, and then a standard curve is prepared within the linear range.
The linear range of the reagent item mainly depends on the concentration of the tool enzyme, and the concentration of the main tool enzyme determines the cost price of the reagent. The tool enzymes of some domestic reagents are generally low, so the linear range is very narrow and the price is relatively low. The SYSMEX reagents have a higher content of tool enzymes, a wide linear range, and a relatively high price.
The main task of the clinical laboratory department is not only to detect specimens with normal results, but also to detect specimens with abnormal results at the first time, which can be more helpful for clinical diagnosis and monitoring of disease prognosis.
The concentration of tool enzymes in SYSMEX's creatinine reagents is higher than that of domestic reagents. The concentration of creatinine aminohydrolase in R1 reaches 100 units/ml (some domestic reagents are 60 units/ml), and the concentration of creatinine amidohydrolase in R2 The concentration is 500 units/ml (some domestic reagents are 300 units/ml), causing the linear range of SYSMEX's creatinine reagent to reach 7074umol/L (some domestic reagents are 0-1400).
When encountering patients with uremia, the creatinine concentration in the blood can reach more than 1800umol/L, which is far beyond the detection range of domestic reagents. If the linear range of the reagent items is too narrow, it will cause trouble to the operator. It is often necessary to increase the sample volume or dilute the sample and retest, which increases the cost of the test.
The concentration of hexokinase in SYSMEX's glucose reagent is 8500 units/ml (some domestic reagents are 2500 units/ml), and its linear range can reach 50mmol/L (some domestic reagents are 0-22mmol/L). Domestic reagents If the glucose oxidase method is used, the linear range is even lower.
Sometimes the blood sugar level of clinically critical patients with diabetes can reach more than 25mmol/L, which exceeds the detection range of domestic reagents. If you want to get accurate results, the specimen must be diluted and retested, which virtually prolongs the time for reporting and waiting. , which is very detrimental to rescuing patients.
The concentration of the tool enzyme --- hexokinase used in the CK imported reagents is 16 units/ml (the HK concentration in some reagents is 5.8 units/ml), and the tool enzyme --- hexose in the CK-MB imported reagents The concentration of kinase is 17 units/ml (the HK concentration in some domestic reagents is 2.5 units/ml), which makes the linear range wider, reaching more than 3000 units/L (the CK in some domestic reagents is 0-1500U/ L, CK-MB is 0-250U/L).
This can promptly report the patient's true results to the clinic when rescuing patients with acute myocardial infarction (CK may exceed 2000U/L, CK-MB may exceed 1500U/L), thereby saving time for rescue.
In summary, the concentration of the main tool enzyme in the reagent determines the width of the linear range, and the concentration of the tool enzyme determines the actual manufacturing cost. It can be seen that to a certain extent, the width of the linear range is positively related to the price of the reagent.
On the surface, using domestic reagents can save costs. However, using domestic reagents with a narrow linear range will cause trouble to the operator. Reexamination of high-concentration specimens will waste a lot of manpower, reagents, and time, and increase the possibility of errors. The probability also increases the cost virtually.
The use of reagents with a wide linear range can save manpower, material resources, and time, improve the operator's work efficiency, free them from tedious repetitive work, and do more valuable things within limited working time.
