Platelet and erythrocyte agglutination is known to happen in vitro due to EDTA or temperature-induced cold antibodies. Leukocyte agglutination is far less common, and its etiology is not always known. The 2 cases presented herein are of low-grade B-cell lymphomas consistent with splenic marginal-zone lymphoma that presented with lymphocyte agglutination. In Case A, the lymphocyte aggregates were not resolved by warming the sample or by non-EDTA anticoagulation. In Case B, the lymphocyte aggregates were largely resolved by warming the specimen at 37°C for 15 minutes. The 2 cases presented herein further show that the etiology of lymphocyte aggregation can have multiple causes, even within the same disease process.

The physiology of hemostasis is one of high complexity that involves the initiation, amplification, and propagation of the many moving parts of the hemostatic system and its regulatory mechanisms. It is imperative that clinical laboratory professionals have a strong understanding of the many intricacies of the physiology of coagulation and its in vitro testing. An elongated activated partial thromboplastin time can have several causes, and the correct cause must be elucidated in a timely manner for proper treatment. A mixing study with normal pooled plasma should be performed to evaluate for the presence of an inhibitor vs factor deficiency. Factor inhibitors, specifically factor VIII in this case study, should be titered so that the clinician can decide which treatment may work best for the patient. Continued monitoring of factor levels and inhibitor titers should be conducted to follow the resolution or progression of inhibitor presence.