What is ISO Accreditation for Labs?

ISO accreditation

 ISO accreditation for testing and calibration labs.

Laboratories around the world process and analyze hundreds of thousands of samples each day. Without an assurance of competency and accuracy, those results could be called into question, risking the world’s health, safety and economy. Since the 1940s, the International Organization for Standardization (ISO) has become one of the world’s largest developers of voluntary international standards from all manners of manufactured, agricultural and technological products and services. In the 1990s, ISO began creating standards for laboratories to standardize procedures and ensure competency and accuracy. Through the years, laboratories and reference material providers have pursued ISO accreditation for their facilities as a mark of quality and reliability.

What is lab accreditation?

Accreditation is the confirmation of the competence of a testing or calibration laboratory or reference material (RM) producer by an unbiased independent third-party accreditation body to an ISO international standard.

What is ISO/IEC 17025?

ISO/IEC 17025 is the standard for the ‘General requirements for the competence of testing and calibration laboratories’. This standard is used by testing and calibration laboratories worldwide to demonstrate their technical competence. The standard was originally issued in 1999 and was followed by a second release in 2005. The 2005 version contained five elements: Scope, Normative References, Terms and Definitions, Management Requirements, and Technical Requirements. The main sections of the standard are: Management Requirements and Technical Requirements.

The management requirement section was comprised of documents mainly relating to the quality management system of the laboratory. The technical requirements section related to all the factors relating to the reliability of a laboratory or product including: accuracy, precision, stability, homogeneity, traceability, and uncertainty of the tests, products and calibrations performed in the laboratory.

The standard ISO/IEC 17025:2005 was revised again in 2017 to ISO/IEC 17025:2017.

What is accuracy?

Accuracy is the degree in which a result or measurement correlated to the ‘true value’ while precision is how close measurements or results are to one another. High precision is often associated with reproducibility, while high accuracy is associated with close correlation to the target or true value.

What is stability?

Stability is the state of being non-reactive during normal use. A reference material or reference standard retains it properties in the expected timescale in the presence of expected conditions of the application. An unstable material is one which will corrode, decompose, polymerize, burn, or explode under normal conditions and applications.

What is homogeneity?

Homogeneity is the state of being of uniform composition or character. Reference materials can have two types of homogeneity: in-bottle homogeneity or between-bottle (or lot) homogeneity. In-bottle homogeneity means there is no precipitation or stratification of the material that cannot be rectified by following instructions for use. Some reference materials can settle out of solutions but are still considered homogeneous if they can be re-dissolved into the solution by following the instructions for use (i.e. sonicate, heat, shake, etc.). Between-bottle or lot homogeneity is the homogeneity found between separate packaging units.

What is traceability?

Traceability is the ability to trace a product or service from the point of origin through the manufacturing or service process through to final analysis, delivery and receipt. Reference material producers must ensure that the material can be traced back to a primary standard. A primary standard is a standard of the highest metrological value that is accepted without reference to another standard of the same quality. Secondary standards are standards that are assigned a value by comparison of the same quantity of a primary standard.

What is uncertainty?

Uncertainty is the estimate attached to a certified value that characterizes the range of values where the ‘true value’ lies within a stated confidence level. Uncertainty can encompass random effects such as changes in temperature, humidity, drift accounted for by corrections, and variability in performance of an instrument or analyst. Uncertainty also includes the contributions from within-unit and between-unit homogeneity, changes due to storage and transportation conditions, and any uncertainties arising from the manufacture or testing of the reference material. Uncertainty, however, is not error or mistakes. Error is the difference between the stated measurement and the true value of the measurand. Error causes values to differ when a measurement is repeated.

What are the different types of uncertainty and what do they mean?

There are two basic classifications for types of uncertainty: type A and type B uncertainty. Type A uncertainty is associated with repeated measurements and the statistical analysis of the series of observations. Type A uncertainty is calculated from the measurement’s standard deviation divided by the square root of the number of replicates.

Type B uncertainty is based on scientific judgment made from previous experience and manufacturer’s specifications. There are three common models for type B uncertainty: rectangular, triangular and normal. Rectangular distribution is used when a certificate or other specification is provided and gives limits without specifying a confidence level. Triangular distribution is used when the measurement distribution is symmetrical and when values are close to the target value and not near the boundaries. This distribution is commonly associated with volumetric glassware. The final distribution is normal distribution which is used when an estimate is made from repeated observations of a randomly varying process and an uncertainty is associated with a certain confidence interval. This type of uncertainty distribution is often found with a calibration certificate with a stated confidence level. Reference material providers accredited by ISO/IEC 17025 and ISO 17034 provide certificates using combined and expanded uncertainties within a normal distribution. These certificates contain stated values and the uncertainty associated with that value as well as the contributions to those uncertainties.

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