الفهرس 
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Abstract
Verification of methods and reference intervals is a tool to detect, reduce, and correct errors in a medical laboratory’s prior to the release of patient results, and improve the quality of the results reported by the laboratory.
To demonstrate the quality and reliability of their services, medical laboratories can seek accreditation to ISO 15189: Medical laboratories-Particular requirements for quality and competence.
In order to comply with ISO 15189, at Ain Shams University hospital laboratories, our work aimed at verification of methods and reference intervals for ten routine chemistry analytes as a particular requirement for laboratory accreditation according to the international standard ISO:15198.
The current study included daily processing of IQC materials by automated chemistry analyzers (Beckman CX9 ALX (SN:6252), Beckman Unicell DX-C600 series (SN:3853), Beckman CX9 ALX (SN:6468) and Beckman CX9 Pro (SN:8829) . Three different levels of quality control were included every day, results were analyzed.
In the current study, RE was calculated and compared to TEa. The precision was considered satisfactory when RE was less than TEa.
On the other hand, accuracy was studied using comparison of methods and calculating SE , the method was reported as accurate when the SE was less than TEa.
Another way to study accuracy was to use results of PT and calculate average % bias that should be less than TEa.
Linearity evaluation was studied using a linearity experiment and results were plotted on a linearity plot which showed to be linear for all the ten analytes
Total error of both RE and SE or bias was calculated and compared to TEa .
In our laboratory, verification of reference intervals for routine chemistry analytes was done using CLSI method, in which representative samples were examined from 20 healthy individuals selected by defined inclusion/exclusion criteria using a health questionnaire related to the test being validated, The proposed reference interval was considered statistically valid and could be adopted by the lab as not more than 10% of the results (2/20) were outside the proposed reference range.
As regards uric acid , albumin and creatinine , we established reference range using 120 reference individuals.
For detection of bias between equipments, 40 patient samples covering different concentrations for each analyte were analyzed on 4 analyzerss (Beckman Unicell DX-C600 series (SN:3853),Beckman CX-9 ALX (SN:6252) Beckman CX9 ALX (SN:6468) and Beckman CX9 Pro (SN:8829).
Bias goal was calculated based on biological variation in which(Bias should be< 0.375 (CVI2 + CVg2)1/2 where CVI is intraindividual biological variation and CVg is between individual biological variation.
In our work, there was no significant bias between the four instruments, and in turn all the four instruments can be used interchangeably, follow up of the same patient can be done satisfactorily, irrespective of which of the four instruments has been used.