- What does the term Linearity refer to?
In chemical terms linearity refers to the proportional relationship between response and concentration over a defined range. It is used to describe the highest concentration of analyte that a diagnostic assay can reliably measure.
- What is Calibration Verification?
CLIA define Calibration verification as “The assaying of materials of known concentration in the same manner as patient samples to substantiate the instrument or test system’s calibration throughout the reportable range for patient test results.”
- How do I perform calibration?
The test systems’ instructions should describe the process for performing calibration as well as when and how often it is to be performed.
- What materials should I use to perform calibration?
The test systems’ instructions should specify the number, type and concentration of the calibration material to be used. Calibration material is a solution that contains a known amount of analyte.
- What is the purpose of Calibration Verification?
The purpose of calibration verification is to check whether the test system is providing accurate results throughout the reportable range, at least three levels should be tested – one at the high end of the reportable range, one at the low end of the reportable range and one near the midpoint of the reportable range.
6. How often is Calibration Verification required?
According to CLIA regulations calibration verification is required at least once every 6 months or when;
– A complete change of reagents for a procedure is introduced.
– There is a major preventive maintenance or replacement of critical parts that may influence test performance.
– Control material reflects an unusual trend or shift.
– The labs established schedule for verifying the reportable range for patient test results requires more frequent calibration verification.
7. What if my results are unacceptable?
If calibration verification results are unacceptable you must repeat the test systems calibration procedure and troubleshoot as necessary. After repeating it is good laboratory practice to run controls before resuming patient testing. If the test system is factory-calibrated, consult with the manufacturer.
8. What is the reportable range?
CLIA defines the reportable range as “the span of test result values over which the laboratory can establish or verify the accuracy of the instrument or test system measurement response.”
9. What is the Analytical Measurement Range (AMR)?
The college of American Pathologists (CAP) define the AMR as “the process of confirming an assay system will correctly recover the concentration or the activity of the analyte over the AMR.”