Quality control products cannot be used as calibration products
When it comes to quality control products, it is very familiar to workers in the inspection department. But some users still ask a few questions: Can quality control products be used as calibration products? Is quality control products traceable? This article will provide detailed answers to these two questions.
(1) Quality control products cannot be used as calibration products
1. Definition of quality control and calibration products:
Calibrator (Calibrator): A reference material that is used as an independent variable value in the calibration function.
Quality control products (control products, control fluids): used only for quality control purposes and not for calibrating the specimen or solution being analyzed (IFCC).
2. The difference between quality control and calibration:
Calibrators: can provide the basis for the accuracy of a single measurement value, and should have an assigned and known measurement uncertainty. The purpose is to calibrate a measurement system to establish the measurement traceability of the system's measurement results.
Quality Control: Indoor quality control refers to precision quality control and does not provide a basis for accuracy. It may or may not have an assignment; measurement uncertainty is not required. Its purpose is to monitor whether there is a problem with the testing system.
3. The regulatory document describes the relationship between quality controls and calibrators:
6.3 Relationship to calibrators in the "Guidelines for Indoor Quality Control for Quantitative Determination in Clinical Laboratories": Quality controllers are different from calibrators, and quality controllers must never be used as calibrators.
Summary: From the definition, we can directly see that QCs and calibrators are completely different. The difference between the two is that calibrators provide a basis for accuracy and have a known measurement uncertainty, while QCs do not provide a basis for accuracy and have no known measurement uncertainty. And the regulatory document also clearly states the relationship between the two.
(2) Indoor quality control products are precision quality control products and do not require traceability.
1. Definition of traceability:
Traceability: A property by which the value of a measurement result or measurement standard can be linked to a specified reference standard, usually a national or international standard, through an uninterrupted chain of comparisons with a specified degree of uncertainty.
Continuous comparison chain: Refers to measurement procedures and calibrators that alternate from low to high metrological levels.
Reference standards: usually national or international standards (with a given degree of uncertainty at each step of the comparison).
2. Description of traceability in regulatory documents:
ISO 17511 file title: In Vitro Diagnostic Medical Products - Measurement of Quantities in Biological Samples - Metrological Traceability for Assignment of Calibrators and Controlled Substances The document states in the introduction that the traceability is required for "correctness control substances", not general controlled substances. General controlled products with or without a fixed value are not traceable. It is pointed out at the beginning of the first chapter of the document that this standard does not apply to:
Control substances that are not assigned a value and are used only to evaluate the precision, repeatability, or reproducibility of a measurement procedure (Precision Control Substances).
● Control substances for internal quality control in laboratories with recommended acceptable value intervals. Each interval is measured by each laboratory using a specific measurement procedure to form each interval and extreme value, without metrological traceability.
The accuracy of controlled substances should meet the following requirements:
The substrate should be similar to the sample measured under the controlled measurement procedure.
This is in contrast to the requirement to have calibrators that are metrologically high, which can be high-purity components, often in a single substrate.
● Assignment, measurement uncertainty, and use adaptation.
In principle, the accuracy of measurements must be verified using correctness control substances; therefore, the transfer scheme for assigning values to correctness control substances should be similar to that for assigning calibrators.
In addition, to control the use of the substance according to the accuracy, the assignment scheme of the given level or higher when assigning values to the corresponding product calibrators should be used, and the value should be more stringent than that of the calibrators.
Summary: There are no traceability requirements in the ISO 17511 document for the control substances (precision control substances) used in the laboratory for indoor quality control on a daily basis. The ISO standard for the traceability requirements of control substances (ISO 17511) is only applicable to the control substances used to evaluate the "detection accuracy". Recommended reading:The difference between quality control and calibration
