Making a diagnosis when labs and clinical findings don’t correlate

March 2, 2021
Marian Freedman

Marian Freedman is a freelance writer.

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Jon Matthew Farber, MD

Dr Farber is a pediatrician in Woodbridge, Virginia.

Contemporary PEDS Journal, Vol 38 No 3, Volume 38, Issue 03

When laboratory results and clinical findings don't match, careful examination is required.

A case report illustrates the importance of carefully evaluating the diagnosis when laboratory results do not match up with clinical signs and symptoms.1 It describes how results of a complete blood count for a girl aged 5 years, whose parents were concerned about her short stature, confirmed a diagnosis of thrombocytopenia. However, the child had no personal or family history of bleeding diathesis, and the blood test revealed many small platelet clumps, which were highly suggestive of ethylenediaminetetraacetic acid (EDTA)-dependent pseudothrombocytopenia. A new blood sample was divided into an EDTA microtainer and a citrate container for immediate testing. Small platelet clumps again were seen in the EDTA but not in the citrate sample. This and other blood sample findings supported the diagnosis of EDTA-dependent pseudothrombocytopenia. This condition is a laboratory artifact caused by the presence of antiplatelet antibodies in the patient’s serum.

Thoughts from Dr. Farber

Remember this pearl should this situation ever come up. More importantly, no matter how much faith you may put in lab testing, remember that an unexpected finding does not automatically mean you missed something on your history and examination; the error may lie in the technology.

Reference

  1. Lee ACW. Pseudothrombocytopenia: what every clinician should know. Pediatr Neonatol. Published online December 15, 2020.
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