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Difficulty: MediumOrdering Laboratory Tests

Match each patient's clinical presentation with the most appropriate diagnostic laboratory test to order to confirm the suspected underlying hematologic condition.

  • A 29-year-old woman presenting with rapidly progressive fatigue, jaundice, and a peripheral smear showing numerous spherocytes and polychromasia.Direct antiglobulin (Coombs) test
  • A 38-year-old man presenting with acute confusion, fever, petechiae, and a peripheral smear demonstrating numerous schistocytes.ADAMTS13 activity assay
  • A 34-year-old man presenting with chronic fatigue, episodic dark morning urine, and a recent unprovoked intra-abdominal venous thrombosis.Flow cytometry for GPI-anchored proteins (CD55/CD59)
  • A 24-year-old asymptomatic man found to have a mild microcytic anemia with normal serum ferritin and total iron-binding capacity on routine screening.Hemoglobin electrophoresis

Answer

Match Autoimmune Hemolytic Anemia presentation to the Direct antiglobulin (Coombs) test; Thrombotic Thrombocytopenic Purpura presentation to the ADAMTS13 activity assay; Paroxysmal Nocturnal Hemoglobinuria presentation to Flow cytometry for CD55/CD59; and suspected Thalassemia trait to Hemoglobin electrophoresis.
Each clinical vignette provides classic findings for a hematologic disorder that requires a highly specific confirmatory laboratory test. The 29-year-old with spherocytes has autoimmune hemolytic anemia, confirmed by a direct antiglobulin test. The 38-year-old with schistocytes and neurological symptoms has TTP, confirmed by an ADAMTS13 assay. The 34-year-old with dark morning urine and abdominal thrombosis has PNH, confirmed by flow cytometry for GPI-anchored proteins. The asymptomatic 24-year-old with microcytosis and normal iron stores has thalassemia minor, confirmed by hemoglobin electrophoresis.

Step-by-Step Solution

1
Analyze each clinical vignette and peripheral blood smear description to identify the most likely underlying hematologic diagnosis.
The vignettes describe classic presentations for autoimmune hemolytic anemia (AIHA), thrombotic thrombocytopenic purpura (TTP), paroxysmal nocturnal hemoglobinuria (PNH), and thalassemia minor.
Accurate clinical pattern recognition is required before selecting the targeted confirmatory laboratory evaluation.
2
Determine the specific diagnostic laboratory test required to definitively confirm each identified condition.
AIHA requires a direct Coombs test, TTP requires an ADAMTS13 assay, PNH requires flow cytometry, and thalassemia trait requires hemoglobin electrophoresis.
Ordering the correct confirmatory assay prevents unnecessary testing, reduces cost, and ensures timely initiation of condition-specific therapy.

Key Concept

Ordering targeted diagnostic laboratory tests for specific hemolytic and microcytic anemias based on distinct clinical presentations.
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Topics

Ordering Laboratory Tests

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