Standardisation and quality assurance

Quality assurance is an essential part of laboratory practice, both in research and clinical diagnosis. The principles and practice of quality assurance (QA) in laboratory medicine in general (1), and in clinical chemistry in particular (2) have been described elsewhere and are widely acknowledged as being a key feature of good laboratory practice. The theoretical aspects of standardisation and QA of immunoassays have been discussed in a series of papers presented at the first Bergmeyer Conference (3). This chapter focuses on practical aspects of QA that are particularly important for the immunoassayist — these include assay standardisation, (sometimes referred to as calibration) internal quality control (IQC) and external quality assessment (EQA). These activities merit careful consideration in relation to immunoassay, not only because of the widespread use of the technique, but more importantly because of the particular problems that arise from the use of biological materials as calibration standards, quality control materials and reagents, for the quantitation of structurally complex analytes. In the following discussion particular reference will be made to the uses of immunoassays in endocrinology, although the principles are broadly applicable.