What are the methods for diagnosing sickle cell disease?

Diagnosis of Sickle Cell Disease

Primary Diagnostic Method

Sickle cell disease is diagnosed through comprehensive hemoglobinopathy screening using high-performance liquid chromatography, capillary electrophoresis, mass spectrometry, or gel electrophoresis, which must be confirmed by a second test such as solubility testing or electrophoresis on agar in citrate buffer. 1

Newborn Screening and Initial Detection

• Most patients in developed countries are identified through newborn screening programs, which can detect sickle cell disease where available 1, 2
• Hemoglobin electrophoresis serves as the gold standard confirmatory test, identifying hemoglobin S and distinguishing between different genotypes (HbSS, HbSC, HbS-β⁰-thalassemia) 3
• In unscreened populations, diagnosis occurs when patients present with unexplained severe atraumatic pain or normocytic anemia 2

Critical Diagnostic Pitfall

Never use a positive sickle solubility test in isolation for diagnosis, as it does not differentiate between heterozygous (sickle cell trait), compound heterozygous, or homozygous states. 1 The solubility test can also give false negative results in neonates or heavily transfused patients 1

Confirmatory Testing Algorithm

1. Initial screening: Perform hemoglobinopathy screen using HPLC, capillary electrophoresis, mass spectrometry, or gel electrophoresis 1
2. Confirmation: Always confirm with a second test—either solubility testing or electrophoresis on agar gel 1, 4
3. Timing consideration: Diagnosis should be made as early as possible, ideally in the first day of life to prevent complications 4

Essential Baseline Laboratory Evaluation

Once diagnosis is suspected or confirmed, obtain:

• Complete blood count to assess for normocytic normochromic anemia, elevated white blood cell counts, and establish baseline hemoglobin levels 1, 3
• Reticulocyte count to evaluate bone marrow response to hemolysis and assess appropriateness of erythropoietic response 1, 3
• Hemolysis markers including total and direct bilirubin 1
• Renal function tests (BUN, creatinine) to evaluate for kidney injury 1
• Liver function tests (AST, ALT, alkaline phosphatase) to assess hepatobiliary involvement 1
• Coagulation studies (PT, PTT) to evaluate for coagulopathy 1
• Urinalysis to check for hematuria, proteinuria, or signs of urinary tract infection 1

Extended Red Cell Antigen Profiling

Obtain an extended red cell antigen profile by genotype or serology at the earliest opportunity, optimally before the first transfusion, including at minimum K, Jk^a/Jk^b, Fy^a/Fy^b, and other relevant antigens. 1 Genotyping is strongly preferred over serologic phenotyping because it provides additional antigen information and increased accuracy, particularly for C antigen determination and Fy^b antigen matching 1. A serologic phenotype may be inaccurate if the patient has been transfused in the last 3 months 1

Important Diagnostic Considerations

• Baseline laboratory values should be established and documented for future comparison, as many patients with SCD have chronic abnormalities 1
• Laboratory abnormalities must be interpreted in the context of the patient's clinical presentation 1
• Clearly communicate the diagnosis of SCD on all laboratory request forms to ensure appropriate processing and interpretation 1
• In heterozygous subjects presenting with pathological manifestations, more sophisticated biochemical tests or molecular biology investigations may be necessary to determine the cause of disease 4