Should You Test for Sickle Cell Disease?
Yes, you should test this 35-year-old African American woman with chronic CBC abnormalities for sickle cell disease or trait using hemoglobin electrophoresis or high-performance liquid chromatography (HPLC).
Why Testing is Indicated
Given her demographic profile and persistent hematologic abnormalities, this patient has two key risk factors that warrant immediate screening:
- Ethnicity: African Americans have the highest prevalence of sickle cell disease in the United States, with approximately 8% carrying sickle cell trait and 1:365 having sickle cell disease 1
- Chronic CBC abnormalities: Unexplained persistent anemia, abnormal red cell indices, or other hematologic findings should prompt consideration of hemoglobinopathies 2
The Testing Approach
First-line test: Order hemoglobin electrophoresis or cation-exchange HPLC 3. These are the gold standard diagnostic tests that can:
- Differentiate between sickle cell trait (HbAS) and sickle cell disease (HbSS, HbSC, HbS-β thalassemia)
- Quantify hemoglobin fractions
- Identify other hemoglobin variants
Do NOT rely on: A simple sickling test (solubility test) alone, as it cannot distinguish between trait and disease states and may give false negatives 1, 3
Additional baseline labs to order concurrently:
- Complete blood count with differential and reticulocyte count
- Peripheral blood smear (look for sickled cells, target cells, nucleated RBCs)
- Hemolysis markers: LDH, indirect bilirubin, haptoglobin
- If HbS is detected and levels suggest disease: extended red cell phenotyping 4
Clinical Significance by Genotype
The test results will have vastly different implications:
Sickle Cell Trait (HbAS - 30-40% HbS):
- Generally benign condition
- May affect A1C interpretation (falsely lowers it by ~0.3%) if she develops diabetes 5, 6
- Requires genetic counseling for reproductive planning
- No specific treatment needed
Sickle Cell Disease (>50% HbS):
- HbSS (sickle cell anemia): Most severe, Hb typically 60-90 g/L, requires comprehensive care 1
- HbSC disease: Moderate severity, higher baseline Hb
- HbS-β thalassemia: Severity depends on β⁰ vs β⁺ variant (HbA2 ≥4.0% helps distinguish) 3
- All require referral to hematology for disease-modifying therapy (hydroxyurea, potentially newer agents)
Important Clinical Pitfalls
If she has undiagnosed sickle cell disease, she is at risk for:
- Acute vaso-occlusive crises and acute chest syndrome
- Chronic organ damage (stroke, pulmonary hypertension, renal disease, avascular necrosis)
- Increased perioperative complications if surgery is needed 1
- Priapism (if male partner/family members) 7, 8
Testing considerations:
- If she has received recent blood transfusions, molecular testing may be needed as transfused cells can obscure results 3
- Hemoglobin electrophoresis at alkaline pH has 100% sensitivity for detecting HbS 3
- Most adults with sickle cell disease are already diagnosed, but approximately 14,000 patients in the UK and many in the US remain undiagnosed, particularly those with milder phenotypes like HbSC or HbS-β⁺ thalassemia 1, 2
Next Steps Based on Results
If positive for sickle cell disease:
- Immediate referral to hematology
- Establish baseline organ function (echocardiogram, transcranial Doppler if indicated, renal function, retinal exam)
- Initiate disease-modifying therapy discussion
- Provide comprehensive education about acute complications 4
If positive for sickle cell trait only:
- Genetic counseling
- Document for future medical care (affects A1C interpretation, relevant for anesthesia at extremes of physiology)
- Partner testing if reproductive planning 5, 6
The combination of African American ethnicity and chronic CBC abnormalities makes this a straightforward indication for testing, as early diagnosis of sickle cell disease significantly impacts morbidity and mortality through preventive care and disease-modifying therapies 1, 4.