Decisions affecting the health, well-being, and employability of individual workers or an employer’s approach to health and safety issues must be based on data of good quality. This is especially so in the case of biological monitoring data and it is therefore the responsibility of any laboratory undertaking analytical work on biological specimens from working populations to ensure the reliability, accuracy and precision of its results. This responsibility extends from providing suitable methods and guidance for specimen collection to ensuring that the results are returned to the health professional responsible for the care of the individual worker in a suitable form. All these activities are covered by the expression of quality assurance.
The central activity in a quality assurance programme is the control and maintenance of analytical accuracy and precision. Biological monitoring laboratories have often developed in a clinical environment and have taken quality assurance techniques and philosophies from the discipline of clinical chemistry. Indeed, measurements of toxic chemicals and biological effect indicators in blood and urine are essentially no different from those made in clinical chemistry and in clinical pharmacology service laboratories found in any major hospital.
A quality assurance programme for an individual analyst starts with the selection and establishment of a suitable method. The next stage is the development of an internal quality control procedure to maintain precision; the laboratory needs then to satisfy itself of the accuracy of the analysis, and this may well involve external quality assessment (see below). It is important to recognize however, that quality assurance includes more than these aspects of analytical quality control.
There are several texts presenting analytical methods in biological monitoring. Although these give useful guidance, much needs to be done by the individual analyst before data of suitable quality can be produced. Central to any quality assurance programme is the production of a laboratory protocol that must specify in detail those parts of the method which have the most bearing on its reliability, accuracy, and precision. Indeed, national accreditation of laboratories in clinical chemistry, toxicology, and forensic science is usually dependent on the quality of the laboratory’s protocols. Development of a suitable protocol is usually a time-consuming process. If a laboratory wishes to establish a new method, it is often most cost-effective to obtain from an existing laboratory a protocol that has proved its performance, for example, through validation in an established international quality assurance programme. Should the new laboratory be committed to a specific analytical technique, for example gas chromatography rather than high-performance liquid chromatography, it is often possible to identify a laboratory that has a good performance record and that uses the same analytical approach. Laboratories can often be identified through journal articles or through organizers of various national quality assessment schemes.