The role of the direct antiglobulin test in pre-transfusion investigations and the approach to selecting blood for transfusion in autoimmune haemolytic anaemia: results of a regional survey.

INTRODUCTION: The aim of this study was to conduct a Regional survey to determine the policies and ways of performing the direct antiglobulin test in pre-transfusion screening, the approach used in cases giving positive results with this test and the technical and operative modalities for choosing blood for transfusion in cases of autoimmune haemolytic anaemia.

MATERIALS AND METHODS: A questionnaire, containing ten multiple-choice questions, was sent to all the transfusion centres in the Region of Tuscany.

RESULTS: The data from all 40 regional centres were analysed. Direct antiglobulin tests and autocontrols were not regularly used in pre-transfusion screening. The direct antiglobulin test was predominantly reserved for suspected cases of autoimmune haemolytic anaemia. Sixty percent of the laboratories characterised the specificity of samples that were positive for IgG and complement by the direct antiglobulin test, 45% that were positive for IgM, 35% also for IgA, and 13% also for subclasses of IgG. Elution studies were reserved (in 18% of laboratories) for those cases in which it was expected that transfusion therapy would be used. In cases of autoimmune haemolytic anaemia, autologous/allogeneic adsorption was carried out in 27% of the structures (the use of proteolytic enzymes is predominant, followed by the "ZZAP" reagent--a mixture of dithiothreitol and an enzyme) and the dilution method in 20%; transfusion of red blood cells with a phenotype extensively compatible (c, C, D, E, e, K, Jka, Jkb, Fya, Fyb, S, s) with that of the recipient is practised in 17% of the centres, while transfusion of units of "least incompatible" red blood cells was reported by 95% of the centres, but in 88% this is preceded by at least one of the above mentioned immunohaematological investigations.

CONCLUSIONS: The organisation of a network of Services of Immunohaematology and Transfusion Medicine can be exploited to overcome some technical and operative limitations of peripheral, dependent Transfusion Sections. The results of this study reveal which immunohaematology laboratory is endowed with the greatest potential and which could, therefore, become the regional reference centre. This investigation could lay the basis for defining behavioural algorithms and recommendations on the issues considered.