Immunocytochemical staining of effusions; an external quality control study in The Netherlands

In The Netherlands an external quality control study of immunocytochemical (IC) staining of effusions was initiated, consisting of three test rounds. The 12 participating laboratories received samples of malignant effusions (runs 1, 2 and 3), and five unstained control specimens prepared from the same material in runs 2 and 3. The laboratories used their own protocols to prepare and stain the samples ('in-house' specimens). Two persons viewed and scored the slides following preset criteria concerning number and morphology of diagnostic cells, background staining and staining specificity. Better scoring results were found for control specimens, compared with 'in-house' specimens, primarily caused by cell loss in the latter. This finding underlines the view that high quality IC needs well organized processing and staining procedures, and warrants external quality control systems.