From the Guidelines
To assess for hemoglobinopathies, a complete blood count (CBC) is the initial test recommended, as it assesses bone marrow function and can indicate abnormalities that warrant further evaluation, including hemoglobin electrophoresis for specific diagnosis 1. When evaluating for hemoglobinopathies, it's crucial to consider the patient's overall clinical presentation and laboratory findings.
- A CBC with differential count provides valuable information on the patient's hematologic status, including anemia, which can be a manifestation of various hemoglobinopathies.
- Abnormalities in the CBC, such as low mean corpuscular volume, can suggest deficiencies of iron, folic acid, and vitamin B12, or inherited disorders of hemoglobin synthesis, as noted in the clinical practice guidelines for evaluation of anemia 1. Key diagnostic tests for hemoglobinopathies include:
- Hemoglobin electrophoresis, which is essential for separating and quantifying different hemoglobin variants.
- Peripheral blood smear, which can reveal characteristic cell morphologies such as sickle cells or target cells. Additional tests like high-performance liquid chromatography (HPLC) and genetic testing for specific mutations may be necessary for a definitive diagnosis and to guide management. It's essential to perform these tests when the patient is in a steady state, avoiding periods of acute illness that could interfere with the interpretation of the results.
From the Research
Blood Tests for Hemoglobinopathies
- Hemoglobinopathies can be diagnosed using a stepwise algorithmic approach, starting with a detailed clinical history and hematologic evaluation, including complete blood count (CBC), reticulocyte count, and red blood cell (RBC) morphology 2
- Protein-based analytic methods such as Hb electrophoresis or isoelectric focusing (IEF), cation exchange high performance liquid chromatography (HPLC), and reversed phase HPLC can be used to identify hemoglobinopathies 2, 3
- Nucleic acid-based methods, including polymerase chain reaction (PCR), reverse transcribed (RT)-PCR, and sequencing of genomic DNA, can also be used to diagnose hemoglobinopathies 2
- High-performance liquid chromatography (HPLC) is a useful method for identifying and quantifying hemoglobin variants, with the ability to separate over 45 commonly encountered variants within 12 minutes 4
- HPLC can provide accurate quantitation of hemoglobin concentrations, including Hb F and A2, which are useful for diagnosing HPFH and beta-thalassemia 4, 5
Specific Tests for Hemoglobinopathies
- Hb electrophoresis and HPLC can be used to identify variant hemoglobins, such as Hb S, C, D-Punjab, O-Arab, E, and Lepore 3
- Isoelectric focusing (IEF) can provide excellent resolution, but is labor-intensive and lacks accurate quantitation 4
- Special confirmatory tests, such as determination of p50, Heinz body prep, and isopropanol or heat stability tests, can be useful when an abnormality of Hb function or stability is suspected 2
Interpretation of Test Results
- The interpretation of test results requires a comprehensive approach, combining clinical history, hematologic evaluation, and protein-based and nucleic acid-based analytic methods 2, 3
- HPLC results should be interpreted in conjunction with other methods, as rare Hb variants can have similar retention times to common variants 5