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Questions and Answers
What are control materials in the context of quality control programs?
What are control materials in the context of quality control programs?
Samples tested every day when testing is done.
What types of quality control are mentioned?
What types of quality control are mentioned?
Pooled sera needs to be __________ to check for errors of bias.
Pooled sera needs to be __________ to check for errors of bias.
prepared
What specimens should be excluded when collecting pooled sera?
What specimens should be excluded when collecting pooled sera?
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At what temperature should pooled sera be stored after preparation?
At what temperature should pooled sera be stored after preparation?
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Commercially prepared control sera are only available in liquid form.
Commercially prepared control sera are only available in liquid form.
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To avoid contamination, do not use __________ pipettes for freeze-dried control sera.
To avoid contamination, do not use __________ pipettes for freeze-dried control sera.
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Match the types of errors with their definitions:
Match the types of errors with their definitions:
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What is the primary goal of quality assurance (QA)?
What is the primary goal of quality assurance (QA)?
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External quality control can substitute for internal quality control.
External quality control can substitute for internal quality control.
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What is the definition of an error in quality control?
What is the definition of an error in quality control?
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Study Notes
Control Materials (Control Sera)
- Used in quality control (QC) programs
- Defined as a sample tested daily during testing
- Called control sera
- Quality control methods divided into:
- Internal quality control
- External quality control
Internal Quality Control
- Performed by the lab itself
- Achieved in two ways:
- Control sera (pooled sera/specimen)
- Commercially prepared control sera
Pooled Sera
- Used to check for bias (inaccuracy) in tests
- Preparation process:
- Collect specimens from the lab with normal results in a screw cap container
- Exclude specimens that are icteric (jaundiced), cloudy (lipemic), pink (hemolyzed), or with abnormal color (dyes)
- Perform HB antigen test on all specimens
- Freeze collected pooled sera daily, up to 1 liter or enough for 4 to 6 months
- Let the pooled sera dissolve completely at room temperature
- Transfer to a large bottle and mix thoroughly
- Send pooled sera for hepatitis antigen test
- If positive, discard sera
- If negative, continue preparation
- Add preservative (100 mg sodium fluoride/dl of serum or 1 ml sodium borate merthiolate/dl of serum)
- Mix well
- Centrifuge for 30 minutes to precipitate fibrin or debris
- Carefully remove supernatant
- If fats appear at the surface, remove them using cotton or glass wool to clear the serum
- Divide the supernatant into small (about 1 ml) containers, label, and freeze at -20°C or less
Commercially Prepared Control Sera
- Available as freeze-dried (lyophilized) or liquid synthetically manufactured sera
- Freeze-dried control sera:
- Preserved at 2-8°C
- Read instructions before use
- Open slowly to avoid loss of substances
- Use good quality glassware and special diluents
- Mix well; leave at room temperature for 5-10 minutes; distribute into small sterile containers (0.5-1ml)
- Do not use manual pipettes to avoid contamination
- Label, freeze, and store at -20°C until needed
Comparison of Pooled and Commercially Prepared Sera
| Feature | Pooled Sera | Commercially Prepared Sera |
|---|---|---|
| Advantage | Very inexpensive | Safe to use |
| Disadvantage | Biological hazard (infection) | Expensive; in some analysis, animal sera may not act exactly as human sera |
Control (pooled + commercially)
- Detect errors in reagents and standard test dilutions (STDs), but not individual pipetting or calculation errors
Quality Assurance (QA) vs. Quality Control (QC)
| Feature | QA | QC |
|---|---|---|
| Focus | Preventing errors | Identifying errors |
| Goal | Improve development and testing procedures to prevent errors during the test | Identify errors in the laboratory tests after they've been performed and before they're released |
External Quality Control
- A quality checking system using an external organization
- Not a substitute for internal quality control because it can only assess past performance
What is an Error?
- Failure of a planned action to achieve its desired goal without external factors causing the failure
Analytical Errors
- Errors of Bias (inaccuracy, systematic, regular):
- Unsatisfactory reagents or standards (preparation, storage, impure, expired)
- Incorrect calibration
- Incorrect wavelength
- Poorly written procedure
- Errors of Scatter (imprecision, random, irregular):
- Faulty technique (pipetting, mixing, incubation)
- Dirty tubes, pipettes, or glassware
- Heavy or low workload
- Fluctuating electricity and temperature
- Finger spots on cuvettes and air bubbles
- Incomplete removal of interfering substances (e.g., red blood cells (RBCs))
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Description
This quiz covers the use of control sera in quality control programs, detailing internal and external quality control methods. It explains the preparation of pooled sera for bias checking in laboratory tests and the importance of proper specimen handling. Discover the key processes involved in maintaining accuracy in laboratory testing.
