1. The laboratory should develop a comparative testing plan for internal quality control based on the needs of the annual quality control plan.

2. In the comparison test plan used for internal quality control in the laboratory, the testing items, comparison forms, participants, expected dates, result evaluation criteria, and requirements for handling unsatisfactory results of each comparison test should be clearly defined.

3. When conducting comparative experiments, the laboratory should take necessary measures to prevent fraud, collusion, or correction of results.

4. After the comparative experiment is completed, the laboratory should summarize, analyze, and evaluate the results of the comparative experiment, and form a comparative experiment report.

5. The laboratory should conduct a root cause analysis of the problems that arise during the comparative testing, and take corrective, preventive, or corresponding improvement measures based on their impact on the laboratory's test results.

1、Personnel comparison

Personnel comparison test refers to a test conducted by different testing personnel on the same sample under the same environmental conditions, using the same testing methods, equipment, and facilities.

When a certain experiment can be operated by multiple people, the laboratory can use personnel comparison experiments for internal quality control. By arranging two or more representative people at different levels to conduct the experiment, the ability level of the testing personnel is assessed, and whether the testing personnel operate correctly and proficiently is judged. This is used to evaluate the impact of personnel on the accuracy, stability, and reliability of the test results.

As a means of internal quality control in the laboratory, personnel comparison is preferred for the following situations:

1) Items that rely heavily on subjective judgment by testing personnel, such as sensory and tasting items in food;

2) Trained employees and newly hired employees;

3) Key control points or critical control links in the detection process;

4) Projects and/or samples with high operational difficulty;

5) The detection result is near the critical value;

6) Newly installed equipment;

7) Newly opened testing items.

2、Method comparison

Method comparison experiment refers to the testing of the same sample using different detection methods under the same environmental conditions and with the same personnel.

When a testing item can be operated by multiple methods, the laboratory can use method comparison for internal quality control to determine whether the standards or methods followed in the testing are strictly understood and implemented, in order to evaluate the impact of the testing method on the accuracy, stability, and reliability of the test results.

As a means and method of internal quality control in the laboratory, comparison is preferred for the following situations:

1) Newly implemented standards or methods;

2) New technologies, methods, and research methods introduced;

3) Existing projects with multiple inspection standards or methods.

3、Instrument comparison

Instrument comparison test refers to an experiment in which the same sample is tested using different instruments and equipment by the same testing personnel in the same environment and method.

When a certain experiment can be operated by multiple devices, the laboratory can use equipment comparison testing to conduct internal quality control, determine whether the equipment that affects measurement accuracy and effectiveness meets the requirements of measurement traceability, and evaluate the impact of instrument equipment on the accuracy, stability, and reliability of laboratory test results.

As an internal quality control measure, equipment comparison testing is preferred for the following situations:

① Newly installed equipment;

② The repaired equipment;

③ Devices with detection results appearing near the critical value.

4、Retain samples for retesting

Retained sample retesting refers to the experiment in which the same testing personnel conduct retesting on the completed samples during their retention period, using the same testing methods, equipment, and facilities under the same environmental conditions as much as possible.

The laboratory compares and analyzes the differences between the previous test results and the current test results by re measuring the retained samples, in order to discover the impact of accidental factors on the accuracy, stability, and reliability of laboratory testing results.

As an internal quality control measure, sample retention and retesting can be used in the following situations:

① Verify the accuracy of the test results;

② Verify the repeatability of the test results;

③ Monitoring the characteristics of retained samples.

Source: Laboratory ISO17025