What tests should be ordered for a possible diagnosis of sickle cell anemia?

Diagnostic Testing for Sickle Cell Anemia

Order hemoglobin electrophoresis or high-performance liquid chromatography (HPLC) as the definitive diagnostic test, confirmed by a second method such as solubility testing or electrophoresis on agar in citrate buffer. 1

Primary Diagnostic Tests

The diagnosis requires a comprehensive hemoglobinopathy screen using one of the following methods 1:

• High-performance liquid chromatography (HPLC) 1
• Capillary electrophoresis 1
• Mass spectrometry 1
• Gel electrophoresis 1

Critical caveat: A positive sickle solubility test alone is insufficient for diagnosis, as it cannot differentiate between sickle cell trait (heterozygous), compound heterozygous states, or sickle cell anemia (homozygous). 1 The solubility test may also give false negative results in neonates or heavily transfused patients. 1

Essential Baseline Laboratory Studies

Once sickle cell disease is suspected, order the following to establish baseline values and assess disease severity 2, 1:

Complete Blood Count (CBC)

• Assesses for normocytic normochromic anemia 1
• Evaluates hemoglobin level, white blood cell count, and platelet count 2
• Essential for comparison during acute presentations 3

Reticulocyte Count

• Evaluates bone marrow response to hemolysis 2, 1
• Reflects the appropriateness of erythropoietic response 2
• Often elevated in sickle cell anemia 3

Hemolysis Markers

• Total and direct bilirubin 1
• Lactate dehydrogenase (LDH) 3
• Aspartate aminotransferase (AST) 3, 1

Organ Function Assessment

• Renal function tests (BUN, creatinine) to evaluate for kidney injury 1
• Liver function tests (AST, ALT, alkaline phosphatase) to assess hepatobiliary involvement 1
• Urinalysis to check for hematuria, proteinuria, or urinary tract infection 1

Newborn Screening Context

All 50 U.S. states, the District of Columbia, Puerto Rico, the U.S. Virgin Islands, and the U.S. military have newborn screening programs capable of making a definitive diagnosis of sickle cell disease at birth. 3 If newborn screening results are available, confirm they are documented in the medical record. 3 For children born outside the United States or adolescents without documented screening, hemoglobin electrophoresis should be ordered. 3

When to Reserve Hemoglobin Electrophoresis

In patients with established sickle cell disease, hemoglobin electrophoresis should be reserved for select scenarios when diagnosis is uncertain, as most patients already have established diagnoses. 2 However, for initial diagnosis in a patient with suspected but unconfirmed disease, this test is essential. 1

Common Diagnostic Pitfalls to Avoid

• Never rely on sickle solubility testing alone for diagnosis—it cannot distinguish between trait and disease states 1
• Do not skip confirmation testing—the initial hemoglobinopathy screen must be confirmed by a second method 1
• Ensure proper communication—clearly indicate suspected sickle cell disease on laboratory request forms to ensure appropriate processing and interpretation 1
• Consider timing in neonates—solubility tests may be falsely negative in newborns due to high fetal hemoglobin levels 1
• Account for recent transfusions—heavily transfused patients may have falsely negative solubility tests 1