QUALITY ASSURANCE IN LABORATORY HEMATOLOGY

Quality assurance in laboratory haematology includes (a) constant chec king of test reliability by internal quality control, (b) external qua lity assessment by an independent agency to check performance of a num ber of laboratories at intervals in order to obtain a retrospective in dication of their ability and (c) proficiency control by supervision o f the pre-test and post-test phases of laboratory work, from specimen collection to delivery of the report to the clinician. The procedures which comprise quality control are described; these include use of con trol preparations with control charts, CUSUM analysis, constancy of da ily means of the blood count indices of 'absolute values', duplicate t esting, clinical correlation and the important role of the blood film to check the instrument-derived blood count measurements. A descriptio n of the functions of an external quality assessment scheme is based o n the UK National Scheme (UK NEQAS). The blood count and other tests o f general haematology have been used as models to describe the procedu res for qualitative and quantitative tests, low results are analysed a nd performance is assessed. The tribulations and triumphs of NEQAS are described and it is concluded that NEQAS has a vital role in ensuring good laboratory practice in general, and the reliability of the indiv idual laboratories who participate in the scheme. NEQAS, in turn, must ensure its own ability to provide stable materials which are suitable for each test in the programme, and to analyse data correctly. There is also need to take account of the continued expansion of laboratory services as new techniques are introduced and to develop appropriate E QA procedures and materials in order to incorporate these in a compreh ensive scheme.