Anja Kessler (Presenter)
Reference Institute for Bioanalytics
Bio: Dr. Anja Kessler Vice Director of Reference Institute for Bioanalytics Chemist; Experience in development of reference measurement procedures; Organising external quality assessment schemes for clinical laboratories and calibration laboratories in laboratory medicine; Active in national and international projects to establish standardisation on metrological basis.
Authorship: Anja Kessler
Reference Institute for Bioanalytics
| Short Abstract Mass spectrometry is used in laboratory medicine with the aim to improve the quality of clinical test results. Reference measurement procedures based on isotope dilution mass spectrometry are used to assign traceable values to control materials and calibrators for validation of clinical routine procedures and evaluation in external quality assessment schemes. Even if the characteristics of MS allow great accuracy also in clinical routine as demonstrated by intercomparison studies, the laboratories have to validate their methods with special care to ensure the benefits of specificity and accuracy for patient safety. |
Long Abstract
Introduction
The technique of mass spectrometry (MS) is involved in laboratory medicine in Germany for more than 40 years. Initially, it was only used in the specialized field of standardization with the aim of improving the quality of medical laboratory tests.
Methods
With the help of reference measurement procedures based on the principle of isotope dilution mass spectrometry (IDMS) concentrations could be analysed with great accuracy and precision as well as low uncertainty for a variety of analytes.
The reference measurement procedures meet the criteria of international standards (e.g. ISO 15193) and the values correspond to the highest metrological requirements. The methods are used to assign traceable values to control materials and calibrators. In external quality assessment schemes (EQAS), these reference method values are the independent target values for the comparison and evaluation of clinical laboratory testing methods from different manufacturers using different measurement techniques.
Results
It can be demonstrated by several examples from the field of metabolites and substrates (cholesterol, uric acid, creatinine) as well for low-molecular hormones (steroids and thyroid hormones) that the use of reference method target values is a powerful tool to demonstrate traceability of test results of individual laboratories or test procedures offered by the manufacturers according to ISO 17511.
However, for use in clinical practice, reference measurement procedures are not intended and not suitable.
Nowadays the technique of MS is used more frequently to develop procedures used in daily routine of clinical laboratories which are a reasonable alternative to established procedures like immunoassays e.g. in the field of steroids and drugs. Regardless whether the routine methods are commercially available or so-called "in-house" procedures, the use must be linked to the requirements of standards (e.g. ISO 15189) or, especially in Germany, the “Guideline of the German Medical Association in Medical Laboratory Examinations” (RiliBÄK) [1]. Therefore, laboratories that apply MS methods have to participate in interlaboratory comparisons regularly as for other testing methods and pass prescribed acceptance criteria to receive requested certificates.
If one takes the number of participants of EQAS as a basis, MS procedures still play a minor role (0.2 to 4%). Only for some steroids and drugs MS procedures are used more frequently (up to 20%).
If traceable reference method values are available, the evaluations of EQAS demonstrate that MS results of most participants show a good agreement with these independent target values.
However, how can data of surveys be evaluated with regard to their accuracy if no reference measurement procedure is available? Currently this affects the majority of analytes, and this situation has to be considered in evaluation and interpretation of interlaboratory test results with special attention. In this case, the assessment is more difficult; due to the fact that the traceability to reference measurement procedures is lacking the only possibility is the method-specific evaluation.
Conclusions
Although the characteristics of MS allow great accuracy, the laboratories have to validate their methods with special care and to exclude cross-reactions to ensure the benefits of specificity and accuracy for patient safety.
References & Acknowledgements:
[1] German Medical Associastion, Revision of the “Guideline of the German medical association on quality assurance in medical laboratory examinations – Rili-BAEK” (unauthorized translation), J. Lab. Med. 39(1) (2015) 26–69, doi: 10.1515/labmed-2014-0046.
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