What test is used to diagnose sickle cell disease?

Diagnostic Testing for Sickle Cell Disease

Order a comprehensive hemoglobinopathy screen using high-performance liquid chromatography (HPLC), capillary electrophoresis, mass spectrometry, or gel electrophoresis, and confirm with a second test such as hemoglobin electrophoresis on agar gel or sickle solubility testing. 1

Primary Diagnostic Approach

Initial Screening Test

• Hemoglobinopathy screen is the definitive diagnostic test and should use one of the following methods: 1

  • High-performance liquid chromatography (HPLC)
  • Capillary electrophoresis
  • Mass spectrometry
  • Gel electrophoresis

• Newborn screening programs can detect sickle cell disease where available and represent the optimal time for diagnosis 1, 2

Confirmatory Testing (Required)

• A second confirmatory test is mandatory after the initial screen 1
• Acceptable confirmatory methods include: 1
  • Hemoglobin electrophoresis on agar gel in citrate buffer
  • Sickle solubility test
  • Cellulose acetate electrophoresis at alkaline pH 3

Critical Testing Pitfalls to Avoid

Do Not Use Solubility Testing Alone

• Never rely on sickle solubility test as the sole diagnostic method - it cannot differentiate between sickle cell trait (AS), sickle cell disease (SS), or compound heterozygous states (SC, S-beta thalassemia) 1, 3
• Solubility testing can give false negative results in neonates or heavily transfused patients 1
• The test only confirms the presence of hemoglobin S but provides no quantitative information 3, 4

Confirm All Positive Results

• All positive solubility tests must be confirmed by electrophoresis to determine the specific genotype 4
• Specimens with hemoglobin SF or SC may give incorrect differentiation between heterozygous and homozygous states 4

Supporting Laboratory Evaluation

Once diagnosis is established, obtain baseline studies: 1

• Complete blood count - typically shows normocytic normochromic anemia 1, 2
• Reticulocyte count - elevated due to chronic hemolysis 1
• Hemolysis markers - total and direct bilirubin 1
• Renal function - BUN and creatinine to assess kidney involvement 1
• Liver function tests - AST, ALT, alkaline phosphatase 1

Clinical Context

When to Order Testing

• Unexplained severe atraumatic pain in a patient without prior diagnosis 2
• Normocytic anemia of unclear etiology 2
• Family history of sickle cell disease or trait
• Ethnic background from sub-Saharan Africa, India, Mediterranean, or Middle East where prevalence is highest 2

Interpretation Nuances

• Clearly communicate the suspected diagnosis of SCD on laboratory request forms to ensure appropriate processing and interpretation 1
• Baseline laboratory values should be established for future comparison, as many patients have chronic abnormalities 1
• In neonates, high levels of fetal hemoglobin may complicate interpretation 3

Point-of-Care Options for Resource-Limited Settings

• HemoTypeSC is a rapid immunoassay with 99.5% sensitivity and 99.9% specificity that costs less than $2 per test 5
• This can support newborn screening programs in low-resource environments where HPLC is unavailable 5
• However, confirmatory testing with standard methods remains the gold standard 1