Pseudothrombocytopenia after changing insulin therapy in a case with insulin‐dependent diabetes mellitus: A first case report
Authors: Cengiz Beyan, Kürşat Kaptan, Ahmet Ifran
Journal: American Journal of Hematology (2010)

A 36-year-old male patient was evaluated for thrombocytopenia. It was learned from his history that insulin-dependent diabetes mellitus (IDDM) was diagnosed 8 years ago, and Humulin M 70/30 (70% NPH isophan suspension mixed with 30% regular insulin produced with recombinant DNA technology) was started with the doses of 18 units in the morning and 10 units in the evening. Approximately a year and a half ago, Humulin M 70/30 was stopped and NovoRapid FlexPen (Insulin aspart-fast acting human insulin analogue produced with recombinant DNA technology) 8 units in the morning, 12 units in the midday, and 10 units in the evening and Lantus Optipen (insulin glargine-long acting insulin analogue) 12 units at night were started. The patient was not taking any other medication. There was no remarkable finding on physical examination. We observed thrombocytopenia with EDTA and heparinized blood samples, but no thrombocytopenia with a citrated sample. The platelet count tested immediately in a freshly drawn EDTA sample was normal. Huge platelet clusters were observed in a peripheral blood film prepared from EDTA-anticoagulated blood after a 1 hr delay. When we checked previous reports, we noticed that platelet counts were normal before changing insulin: e.g., 243 × 109/L, 148 × 109/L, 278 × 109/L, 225 × 109/L, and lastly 188 × 109/L five months before changing insulin therapy. The platelet count was 41 × 109/L after 2 months of insulin changing. At the same laboratory, blood was recounted freshly (immediately after collection), and at this occasion, the platelet count was 221 × 109/L; these results had been erroneously attributed to coagulation in the first sample. The patient and the doctor managing insulin therapy were informed about the cause of thrombocytopenia was pseudothrombocytopenia, and the possible reason for this situation might be due to change in insulin therapy according to his medical reports. Pseudothrombocytopenia is a condition caused by anti-platelet antibodies in which agglutination of platelets in the complete blood count tube leads to incorrectly low platelet counts. It should be considered first in patients with low platelet counts without a bleeding diathesis. This phenomenon could be observed in healthy subjects, but it could also accompany certain diseases. The incidence is 0.09–0.21% [1]. In most cases, the phenomenon is EDTA dependent. Other anticoagulants, such as heparin and sodium citrate, are reported to cause pseudothrombocytopenia [2]. We observed pseudothrombocytopenia with both samples including EDTA and heparin, but citrate did not cause pseudothrombocytopenia in our patient. According to our literature survey in PubMed, we could not find any report for pseudothrombocytopenia related with IDDM and/or insulin or insulin analogue therapy in PubMed. Proving that the pseudothrombocytopenia is due to the change in insulin would require discontinuing the insulin or switching the patient back to the old formulation of insulin, and determining if the pseudothrombocytopenia resolves. However, the first option is not feasible, and the second option is not necessary for clinical care, and therefore, it has not been attempted. Pseudothrombocytopenia is a condition that might accompany insulin therapy in patients with diabetes mellitus. It should be considered in patients with thrombocytopenia but without bleeding. Cengiz Beyan*, Kürşat Kaptan*, Ahmet Ifran*, * Department of Hematology, Gulhane Military Medical Academy Ankara, Turkey.