When selecting standard samples for calibrating cholesterol machines, it is necessary to comprehensively consider multiple key factors such as sample accuracy, stability, traceability, applicability, and supplier reputation to ensure the reliability and effectiveness of calibration. The specific points are as follows:
Accuracy and reliability of value setting
- Traceability to authoritative standards: The value setting of standard samples should be traceable to internationally or nationally recognized authoritative standards, such as those established by the World Health Organization (WHO) and the National Institute of Standards and Technology (NIST). This ensures the accuracy and reliability of cholesterol concentration in the sample, making the measurement results of the calibrated cholesterol machine traceable and consistent.
- After a strict value setting procedure: Select standard samples produced by professional institutions or well-known manufacturers. These samples have been measured by a variety of accurate and reliable analytical methods during the value setting process, and have undergone strict quality control and audit processes. For example, high-precision methods such as isotope dilution mass spectrometry are used for value setting to ensure the accuracy of the sample cholesterol concentration.
Stability
- Sufficient validity period: Standard samples should have a sufficiently long validity period to meet the calibration use needs within a certain period of time. During the validity period, the cholesterol concentration of the sample should remain relatively stable and will not change significantly over time. Generally speaking, the validity period should be at least one year, which can be selected according to actual usage and procurement plans.
- Good storage stability: Standard samples should be stable under different storage conditions (such as specified temperature, humidity, etc.). For example, some standard samples need to be stored at a specific temperature, such as 2-8℃ refrigeration or -20℃ freezing to ensure that their chemical properties are stable and the cholesterol concentration does not change. When selecting, you should understand the storage requirements of the sample and ensure that the laboratory can provide the corresponding storage conditions.
Matrix effect
- Matrix similar to clinical samples: The matrix of the standard sample should be as similar as possible to the blood sample actually tested in the clinic. The matrix components of blood samples are complex, including plasma proteins, various ions, etc. The matrix of the standard sample is similar to it to reduce the influence of the matrix effect. The matrix effect refers to the interference of other components in the sample other than the analyte on the analytical method. If the matrix of the standard sample is different from that of the clinical sample, it may lead to inaccurate calibration and affect the measurement accuracy of the machine for actual clinical samples.
- No obvious interfering substances: The standard sample should not contain substances that have obvious interference with cholesterol measurement. For example, it should not contain excessively high concentrations of bilirubin, hemoglobin, and other substances that may interfere with the cholesterol detection method, so as not to affect the accuracy of calibration and cause deviations in the machine's measurement results.
Concentration range
- Covering the measurement range: The cholesterol concentration of the standard sample should cover the entire measurement range of the cholesterol machine. Different cholesterol machines have different measurement ranges. Generally, the total cholesterol measurement range is about 1.0 mmol/L - 10.0 mmol/L, the low-density lipoprotein cholesterol (LDL-C) measurement range is about 0.5 mmol/L - 8.0 mmol/L, and the high-density lipoprotein cholesterol (HDL-C) measurement range is about 0.2 mmol/L - 2.5 mmol/L. The selected standard sample should contain cholesterol at different concentration levels of low, medium, and high, which can meet the calibration requirements of the full range of the machine and ensure that the machine can accurately measure within the entire measurement range.
- Have a suitable concentration gradient: If there are multiple standard samples, there should be a suitable gradient between their cholesterol concentrations. For example, setting standard samples with different concentration gradients such as 2.0 mmol/L, 4.0 mmol/L, 6.0 mmol/L, and 8.0 mmol/L can more comprehensively evaluate the measurement accuracy of the cholesterol machine at different concentration levels, making it easier to draw an accurate calibration curve.
Other considerations
- Certification and qualifications: Select standard samples with relevant certifications and qualifications, such as products certified by the State Food and Drug Administration (CFDA) or internationally certified products. These certifications indicate that the quality and safety of the samples have been recognized and can be used with confidence.
- Supplier reputation: Select standard samples provided by reputable suppliers. Suppliers should be able to provide detailed product instructions, quality assurance documents and other information, have a good reputation for after-sales service, and be able to promptly resolve problems encountered during use.