Today marks the final day of July, and what a productive month it has been! At Shanghai Hengyuan, we're excited to announce that our flagship product, the Guinea Pig ELISA Kit, is now officially available. Today, we’ll take a closer look at some common issues encountered during experiments, focusing on the importance of quality control serum and how to properly prepare and use it.
A critical value control serum plays a vital role in ensuring accurate test results. It can either be a fixed or undetermined value. When only one quality control serum is used, it is typically set at the borderline between normal and abnormal values, representing a weak positive level—this is known as the critical value. For hepatitis B markers, the definition of this critical value should align with clinical needs, providing a consistent standard for identifying weakly positive samples.
This type of control serum can act as a positive control within the kit, serving as a third control alongside the negative control. It helps detect even low-level reactions, ensuring no weakly positive samples are missed during testing.
For laboratories preparing their own quality control serum, here’s a step-by-step guide:
1. Collect fresh serum that is free from hemolysis, jaundice, and bacterial contamination.
2. Heat the serum at 56°C for 10 hours to inactivate any potential pathogens.
3. Centrifuge or filter the serum to remove any precipitates.
4. Dilute the collected serum using 10% calf serum or normal human serum (in PBS buffer). Using normal human serum is preferable since its composition closely resembles patient samples.
5. Filter and sterilize the diluted serum, then aliquot it into single-use vials. Seal them tightly and store at -20°C. Avoid repeated freeze-thaw cycles.
The concentration of the control serum should match the detection level required for the target analyte. If additional specifications exist for the test, adjust the concentration accordingly.
When calibrating, collect 20–30 test results and exclude data points that fall more than ±2 SD from the mean. Compare these results with a known reference serum to determine the target value.
For three-level quality control serum, the hepatitis B marker control serum provided by the Ministry of Health's clinical testing center can be stored at -20°C for up to six months. Once thawed, mix thoroughly before use, and any unused portion can be kept at 4°C for five days. Repeated freezing and thawing should be avoided, as well as self-packing.
Indoor quality control serum for specific tests is usually prepared every 3–6 months. Before using up a batch of homemade control serum, ensure the next batch is ready. The serum must maintain stable performance over time, with consistent potency and physical/chemical properties similar to actual patient samples. This ensures reliable monitoring and consistent test outcomes.
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