224 Copyright © 2018 by the University Clinical Centre Tuzla, Tuzla, Bosnia and Herzegovina. 1 Clinical Institute of Laboratory Diagnosis, University Hospital Centre Zagreb, 2 Department of Paediatrics, University of Zagreb School of Medicine, University Hospital Centre Zagreb, Croatia Correspondence: vkusec@kbc-zagreb.hr Tel.: + 385 1 236 7 289 Fax.: + 385 1 236 7 395 Received: November 29, 2017 Accepted: June 18, 2018 Key words: Hormone measurement ■ Measurement methods ■ Immunoassay ■ Quality management ■ Six sigma. Understanding the Basics of Quality Control in the Medical Laboratory – the Impact on Result Interpretation Vesna Kušec 1 , Nataša Rojnić Putarek 2 , Nevena Krnić 2 , Anita Špehar Uroić 2 , Katja Dumić 2 Review article Central Eur J Paed 2018;14(2):224-235 DOI 10.5457/p2005-114.221 Te aim of this paper was to provide information on the limitations of current analytical methods and the basics in quality control in labora- tory endocrinology which afect the results and their interpretation. For the practicing clinical endocrinologist it is important to under- stand the essentials of the quality of hormone measuring methods and their limitations. Awareness of the quality of methods will allow cau- tion and/or ensure the reliability of result interpretation. A measuring method cannot be performed with equal precision and trueness for the entire measuring range, and may difer between parameters and manufacturers. According to the level of medical decision, the medical laboratory should determine the quality of the method and commu- nicate that information to the clinician. Te basic approach to qual- ity control of measurement methods is useful knowledge for doctors working in a hospital setting or private practice. Te advantages and limitations are presented of immunoassay-based methods and tandem mass spectrometry (LC-MS/MS) used for measurement in biochemis- try laboratory. Conclusion – Hormone measurement is widely avail- able but the methods may be afected by limitations. Understanding a method’s limitations and options for improvement enables the prac- ticing clinician to interpret the test results rationally. Introduction Hormone measurement remains an essential aspect of diagnosis and management in paedi- atric endocrinology, in conjunction with imag- ing and molecular diagnostic tests. Laboratory tests have advanced since the introduction of commercial radio-immunoassays for hormone measurement that have ensured the availabil- ity of laboratory tests at reasonable cost. Both methodological improvements and modern technology have been important milestones in laboratory diagnostics, allowing for the current state in which results are obtained in a shorter time and more frequently. Tests are in general more specifc and precise, costs are lower and the development of automated instruments or platforms have helped make laboratory work less demanding for personnel. Tus, every hospital biochemistry laboratory is able to ofer some hormone tests. Moreover, awareness of good clinical and laboratory practice and safety is now an im- portant part of routine health care. In labo- ratory medicine, measurement methods may be standardized, through use of certifed ref- erence materials for assay calibration, or, in the absence of higher-order reference mate- rials, external inter-laboratory quality assess- Medical Laboratory