How to conduct Inter lab comparison as per NABL/ISO/IEC 17025:2017

Inter laboratory comparison is the organization, performance and evaluation of tests on the same or similar test items by two or more laboratories in accordance with predetermined conditions.

Inter laboratory relating to, or engaged in by more than one laboratory.

A inter laboratory comparison (or proficiency test or PTP or round robin test) consists in testing the same samples by different laboratories and in comparing the results. Three different objectives can be pursued: Assess the reliability of the test results of the participating laboratories.

Inter laboratory studies are studies in which several laboratories analyze the same material. The participants apply whatever method is in use in their laboratory. The results of the laboratories are compared to evaluate the proficiency of individual laboratories and to improve their performance.

The participating laboratory must prepare and communicate to NABL a program outline containing details of the artifact / parameters to be calibrated and reference laboratory selected in the reporting Format-A (Annexure A). The laboratory shall select the artifact and calibration points in a manner to cover the entire range of the accredited scope.

The participating laboratory has to select a reference laboratory which should be either NPL or another accredited laboratory having better CMC than the participating laboratory in that particular parameter. The laboratory shall ensure that the reference laboratory is preferably not under the same top management.

The artifacts used are shall have excellent repeatability and stability to hold their calibration for the period of the activity. Further the artifacts shall have range as per scope, sufficient resolution, to allow the laboratory to report an uncertainty equal to their CMC as defined in their scope of accreditation/ application. The laboratory shall not report uncertainty better than their accredited / claimed CMC. The reported uncertainty for participating and reference laboratory shall be close to or equal to their CMCs

The participating laboratory shall communicate the calibration results to NABL in Format A along with the calibration certificate for approval of the program before sending the artifact to Reference Laboratory.


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