EDTA‐dependent lymphoagglutination

A 84-year-old man, who had suffered from chronic myelomonocytic leukaemia for 2 years, complained of fatigue and abdominal pain. His complete blood cell count showed Hb 7 ́6 g/dl, white cell count 15 ́8 10/l and platelet count 232 10/l. The scatter plot of the automated analyser showed an abnormal distribution of lymphoid cells. A peripheral blood smear made from EDTA-anticoagulated blood revealed clumping of lymphocytes, with intriguing ringed-shaped clusters (top and bottom). The remaining leucocytes were morphologically normal. Leucoagglutination is a rare EDTA-dependent phenomenon, which usually involves neutrophils and results in a spurious decrease of the automated leucocyte count. Lymphocyte agglutination is far less frequent than neutrophil agglutination. It has been reported in lymphoproliferative disorders, infections, alcoholic liver disease and auto-immune diseases, but can also occur in the absence of any apparent relevant disease. EDTA-induced membrane conformational changes with exposure of cryptoantigens has been suspected as the cause. Lymphocyte aggregates are usually round rather than ring-shaped.