What tests are used to diagnose hemolysis?

From the Guidelines

Diagnosing hemolysis involves a comprehensive approach that includes a complete blood count (CBC), peripheral blood smear examination, and biochemical markers such as lactate dehydrogenase (LDH), indirect bilirubin, and haptoglobin, as well as specialized tests like the direct antiglobulin test (DAT) and enzyme assays for deficiencies like G6PD, as recommended by the most recent guidelines 1.

Initial Testing

Initial testing for hemolysis typically includes:

• Complete blood count (CBC) to assess hemoglobin levels and reticulocyte count
• Peripheral blood smear examination to reveal abnormal red cell morphology
• Biochemical markers such as elevated LDH, increased indirect bilirubin, and decreased haptoglobin

Specialized Tests

Additional specialized tests may include:

• Direct antiglobulin test (DAT or Coombs test) to identify immune-mediated hemolysis
• Hemoglobin electrophoresis to identify hemoglobinopathies
• Osmotic fragility tests for membrane disorders
• Flow cytometry for paroxysmal nocturnal hemoglobinuria
• Enzyme assays for deficiencies like G6PD

Comprehensive Diagnostic Approach

A comprehensive diagnostic approach, as outlined in the guidelines 1, should also consider:

• History and physical examination
• Blood chemistry
• Disseminated intravascular coagulation panel
• Autoimmune serology
• Paroxysmal nocturnal hemoglobinuria screening
• Evaluation for viral or bacterial causes of hemolysis
• Protein electrophoresis and cryoglobulin analysis
• Work-up for bone marrow failure syndrome if refractory
• Glucose-6-phosphate dehydrogenase level
• Evaluation of common drug causes
• Assessment of methemoglobinemia This comprehensive approach is essential for determining the underlying cause of hemolysis and guiding appropriate treatment, with the goal of minimizing morbidity, mortality, and improving quality of life 1.

From the Research

Tests for Hemolysis

• Laboratory tests that confirm hemolysis include:
  • Reticulocytosis 2, 3, 4
  • Increased lactate dehydrogenase (LDH) 2, 3
  • Increased unconjugated bilirubin 2, 3
  • Decreased haptoglobin levels 2, 3
• The direct antiglobulin test (DAT) is used to differentiate immune causes from nonimmune causes of hemolysis 2, 5
• A peripheral blood smear should be performed to identify abnormal red blood cell morphologies 2, 3, 4
• Additional tests that may be used to diagnose hemolysis include:
  • Marrow erythroid hyperplasia 3
  • Free hemoglobin 3
  • Hemoglobinuria and hemosiderinuria 3
  • Decreased 51Cr red cell half-life 3
• Genetic testing, such as Sanger sequencing or next-generation sequencing, may be recommended if conventional laboratory tests are unable to detect the underlying cause of hemolysis 4