Standardization

Clinical laboratory errors lead to adverse effects on patient diagnosis, therapy and outcomes, also resulting in the inappropriate use of funds. Standardization plays an important role in patient care because it contributes to a decrease in the number of errors, thus improving the harmonization of procedures and comparability between different laboratories. The introduction of the International Standardization Organization (ISO) standards BS EN ISO 9001 (Quality management systems – requirements), BS EN ISO 17025 (General requirements), BS EN ISO 15189 (Medical laboratories – particular requirements for quality and competence) and BS EN ISO 22870 (Point-of-care testing) places quality at the heart of all activities (see also Table 24.8). In the UK, the focus for laboratory practice has been on Clinical Pathology Accreditation (UK) Ltd (CPA), which has evolved to reflect the way service delivery is perceived within pathology and is now linked to UK Accreditation Service. Quality management systems may also include requirements arising from regulations related to blood and tissues and the Good Manufacturing Practice (GMP) guide, while through the ISO standards, there is a move towards international harmonization.

Standardization of haematology laboratory practice plays a pivotal role in patient care and is essential for certification and accreditation. It should include the following topics:

Standardization of procedures and devices used in the haematology laboratory are the concern of the international professional organizations, especially the International Council for Standardization in Haematology (ICSH). The International Organization of Standardization (ISO) and Comité Européen de Normalization (CEN) have also established standards for medical laboratory practice and for the use of in vitro diagnostic medical devices. At a national level, the British Committee for Standards in Haematology (BCSH) publishes guidelines in books, on websites or as journal articles, and in the USA, a wide range of practice guidelines have been published by the Clinical and Laboratory Standards Institute (CLSI) (formerly the National Committee for Clinical Laboratory Standards, NCCLS). Lists of published documents and catalogues from these various organizations can be found on their various websites (see Table 25.2; see also Tables 24.5 and 24.8).

Table 25.2 Some organizations involved in standardization and quality management systems

External quality-assessment schemes have a role in identifying unsatisfactory performance by devices. Some of the terms and definitions generally used in laboratory practice are summarized in Table 25.3.

Table 25.3 Terms relating to quality control in clinical laboratory practice

Control materials and reference standards

The main international authority concerned with material standards (reference preparations) for laboratory medicine is the World Health Organization (WHO). In the European Union, the Institute for Reference Materials and Measurements (IRMM) has established numerous ‘certified reference materials’ for haematology and clinical chemistry. International standards are not intended for routine use but serve as stable standards for assigning values to commercial (or laboratory-produced) ‘secondary standards’ or calibrators.

Control materials are available commercially and they can also be made locally, although there may be technical difficulties in preparing such ‘homemade’ materials. For example, stored plasma may become turbid; chemical or serological analysis may be affected by instability of enzymes; immunological reactions may be interfered with by added preservatives. With the blood count, there are especially difficult problems because of the need to ensure homogeneity in aliquot samples and due to the instability of blood cells, while procedures that enhance the stability of blood samples may also affect the behaviour of the cells. Thus, control material is not strictly analogous to fresh blood. Nonetheless, provided attention is paid to these difficulties, preserved or stabilized blood provides suitable material for internal quality control procedures for haemoglobin concentration, red cell counts, platelet counts and leucocyte counts (see p. 599: Preparation of extended-life material for QA).

Quality assurance procedures

The procedures that should be included in a quality assurance programme vary with the tests undertaken, the instruments used and (especially if these include a fully automatic counting system) the size of the laboratory and the numbers of specimens handled. Also, the computer facilities available and the amount of time that can be devoted to the quality control assurance must be taken into account. At least some form of internal quality control must be undertaken and there must be participation in an external quality assessment scheme where one is available. Some control procedures should be performed daily and other performance checks should be done at appropriate intervals. The latter is particularly important when there is a change in staff and after maintenance service or repair has been carried out on equipment. A comprehensive protocol is summarized in Table 25.5.

Table 25.5 Schedule for quality control procedures

During the last 20 years, automation, standardization and technological advances have significantly improved the analytical reliability of laboratory results with a high level of accuracy and decreased error rates in the blood count assay.

Quality design must begin with analytical quality, as it is the essential quality characteristic of any laboratory test. Analytical variations may arise from unsuspected abnormal binding protein(s) in patients, such as heterophile antibodies, anti-animal antibodies and anti-idiotypic antibodies. The exact effect will depend on the site of the interaction with the reaction, leading to falsely raised or lowered measurements.² More recent data underline the importance of analytical accuracy due to the frequent calibration error that leads to analytical bias affecting the number of patients passing decision thresholds in practice guidelines. The effects of this medically and economically have been demonstrated.³ To ensure reliability in the analytical phase, procedures are required for internal quality control, external quality assessment and standardization. All laboratory staff require training in these various aspects of quality assurance. A useful training manual from WHO* describes the principles and methods, together with practical exercises to illustrate these.⁴ Another good teaching source is J.O. Westgard’s website: www.westgard.com;