EDTA-dependent pseudothrombocytopenia mimicking dengue-associated severe thrombocytopenia: a case report

We report a case of suspected dengue fever that was ultimately diagnosed as ethylenediaminetetraacetic acid (EDTA)-dependent pseudothrombocytopenia in a 24-year-old man presenting with frontal headache, malaise, and recent fever.

A previously healthy 24-year-old man presented with thrombocytopenia, with an initial platelet count of 25 × 10⁹/L. He reported a 1-week history of frontal headache, severe dizziness, generalized weakness, and recent fever. There was no history of bleeding or bruising. Given the degree of thrombocytopenia and a regional increase in dengue cases, dengue fever was the provisional diagnosis. The patient was admitted for further evaluation and conservative management. A peripheral blood smear revealed morphologically normal platelets with marked clumping, raising suspicion of EDTA-dependent pseudothrombocytopenia. Paired blood samples were drawn in EDTA and sodium citrate tubes. The EDTA sample showed a platelet count of 42 × 10⁹/L, whereas the citrate sample showed a count of 191 × 10⁹/L, confirming the diagnosis. The patient remained clinically stable and was discharged. After discharge dengue serology returned back negative.

In patients presenting with thrombocytopenia, the clinical picture is essential in guiding appropriate management. While it is important to maintain a low threshold for suspecting dengue fever, clinicians should also broaden the differential diagnosis to include pseudothrombocytopenia.

This case report serves as a learning example that physicians should remain vigilant for EDTA-dependent pseudothrombocytopenia and request peripheral smears and citrate-based counts in cases of unexplained thrombocytopenia. Awareness of laboratory limitations in addition to correlation with clinical picture is a must for clinicians.