Laboratory comparison and proficiency verification

Laboratory comparison and proficiency verification are powerful supplements to the internal quality control procedures of the testing agency.

Laboratory comparison refers to the organization, implementation and evaluation of tests on the same or similar samples by two or more laboratories in accordance with pre-specified requirements.

Proficiency verification is an activity to determine the accredited testing capabilities of laboratories through inter-laboratory comparisons. It is a comparison between laboratories to determine the ability of a certain laboratory to perform specific tests and monitor its sustainability.

01 Purpose of laboratory comparison and proficiency verification

1. Metrological calibration. Determine the specific capabilities of the laboratory;

2. Provide objective evidence of data reliability and validity for the laboratory, identify laboratory unqualified work and formulate corresponding measures;

3. Determine the validity and comparability methods of new tests;

4. As a technical inspection method, supervise the test results and increase customer confidence;

5. Ensure the traceability requirements of the standard materials or instruments and equipment of the testing agency, or achieve the same value as similar laboratories;

02 Comparison and proficiency verification classification

1. Internal laboratory comparison and proficiency verification

The activity of determining the accredited capabilities of laboratories by comparing inspectors in the laboratory is to evaluate whether the inspectors are competent for the testing methods they are engaged in.

2. Inter-laboratory comparison and proficiency verification

The activity of using inter-laboratory comparison to determine the laboratory's accreditation capabilities is actually a verification activity to evaluate, supervise and confirm the laboratory's capabilities to ensure that it maintains a high level of detection.

3. Equipment comparison

The activity of determining the measurement capability and accuracy of equipment by comparing similar equipment between laboratories.

4. Method comparison

The activity of comparing different test methods for the same test item to determine the accuracy and reliability of different test methods.

03 Selection of comparison items

For comparison and proficiency verification tests organized by testing institutions, the selection of items can be considered from the following aspects:

Customer complaint items

Non-trace instruments and equipment

Project methods using non-standard tests

New projects

Other testing projects with high technical requirements

By comparing between laboratories, problems in the laboratory can be found.

For laboratories that do not meet the requirements for accuracy, the cause can be found from systematic errors or gross errors, such as instrument calibration before measurement, constant environmental errors, container cleanliness, instrument abnormalities, etc.

For laboratories whose accuracy does not meet the requirements, the cause can be found from random errors, such as fluctuations in ambient temperature and instrument stability during measurement.

04 The difference between measurement audits and proficiency verification

1. Definition of proficiency verification

Through comparison between laboratories, the ability of participants is evaluated according to pre-established standards.

Definitions include EQA (external quality assessment or gap assessment), which is commonly used in the medical field and meets this definition.

Proficiency verification, also known as proficiency verification activities, includes various proficiency verification plans, measurement audits, and comparison plans that meet this definition.

2. Definition of proficiency verification plan

In a specific field of detection, measurement, calibration, or inspection, one or more rounds of proficiency verification are conducted on design and operation.

Proficiency verification plans can include one or more specific types of tests, calibrations, or inspections.

3. Definition of investigative audit

The activity in which participants actually test objects (materials or products) and compare the test results with reference values.

Measurement audit is a proficiency verification program that conducts one-on-one capability assessments on participants.

4. Relationship between proficiency verification program and measurement audit

Measurement audit is a special form of proficiency verification program. It is an activity that compares the measurement results of participating laboratories with measurement items (materials or products) with reference values (reference values) and evaluates them according to predetermined standards. Therefore, measurement audit is sometimes called a "one-on-one" proficiency verification program.

The sample issuing unit for proficiency verification or measurement audit should be qualified, that is, a laboratory that operates in accordance with the "Criteria for Accreditation of Proficiency Verification Providers" and has passed the accreditation assessment