Tests
1st tests to order
hemoglobin (Hb)
mean corpuscular volume (MCV)
Test
The MCV correlates with phenotypic and genotypic worsening of the disease. Patients with alpha-thalassemia silent carrier have a normal to slightly low MCV, whereas those with deletional alpha-thalassemia trait usually have an MCV of <78 femtoliters.[48] Those with deletional Hb H disease will have an MCV in the mid-60s.[43] Patients with Hb H/Constant Spring will have an MCV that is normal to mildly low, and those homozygous for Hb Constant Spring will often have a normal MCV.
Result
low
mean corpuscular hemoglobin (MCH)
Test
MCH will be normal to low (24-29 picograms) in those with 1 alpha-thalassemia silent carrier, and it will be low (<27 picograms) in those with >1 alpha-globin deletion or in those with nondeletional mutations. Mean MCH is approximately 20 picograms in Hb H disease.[43]
Result
low
red blood cell count
Test
Should be performed in all patients.
Result
increased; variable, corresponding to severity
peripheral smear
reticulocyte percentage
Test
Elevated (5% to 10%), and may be further increased during acute infections or hemolytic crises.[48]
Result
increased
serum iron
Test
Result
normal or elevated
Tests to consider
brilliant cresyl blue staining of red blood cells
Test
Numerous inclusion bodies are typically seen in Hb H disease.[16] Felt by some experts to be more reliable than Hb electrophoresis for diagnosis of Hb H disease.
May be reduced or absent in the presence of heterozygous beta-thalassemia such as Hb S, Hb C, Hb E, or beta-thalassemia.[43][56]
Result
demonstrates Hb H inclusions in peripheral blood red cells
Hb electrophoresis
Test
Hb H and Hb Bart can be detected as fast-moving hemoglobins. Will not pick up alpha-thalassemia silent carrier or alpha-thalassemia trait outside of the newborn period (Hb Barts), and will not differentiate deletional from nondeletional forms of Hb H (except for Hb Constant Spring). Patients with Hb H disease and concomitant heterozygous beta-hemoglobinopathies such as Hb S, Hb C, Hb E, or beta-thalassemia have low or absent Hb H, which may confound the diagnosis of Hb H disease.
Do not repeat hemoglobin electrophoresis in patients who have a prior result, unless the results of interventional therapies are being monitored or to make a more specific diagnosis.[49]
Result
presence of Hb H, Hb Bart, and concomitant hemoglobinopathies (Hb E, Hb S, Hb C, Hb D)
Hb fractionation by high-performance liquid chromatography (HPLC)
Test
Hb fractionation by HPLC provides fast separation and precise estimation of hemoglobin variants.
Will not pick up alpha-thalassemia silent carrier or alpha-thalassemia trait outside of the newborn period (Hb Barts), and will not differentiate deletional from nondeletional forms of Hb H (except for Hb Constant Spring). Patients with Hb H disease and concomitant heterozygous beta-hemoglobinopathies such as Hb S, Hb C, Hb E, or beta-thalassemia have low or absent Hb H, which may confound the diagnosis of Hb H disease.
Result
presence of Hb H, Hb Bart, and concomitant hemoglobinopathies (Hb E, Hb S, Hb C, Hb D)
gap-polymerase chain reaction (gap-PCR)
Test
Seven of the most common alpha-thalassemia deletions (-alpha(3.7), -alpha(4.2), --(FIL), --(THAI), --(MED), -(alpha)(20.5) , --(SEA)) can be diagnosed by gap-PCR.[48]
If there are existing genetic test results, do not repeat a genetic test unless there is uncertainty about the existing result, for example, the result is inconsistent with the patient’s clinical presentation or the test methodology has changed.[51]
Result
detects specific deletions
multiplex ligation-dependent probe amplification
Test
Used to detect deletions and duplications in the alpha-globin gene cluster causing alpha-thalassemia.[48]
If there are existing genetic test results, do not repeat a genetic test unless there is uncertainty about the existing result, for example, the result is inconsistent with the patient’s clinical presentation or the test methodology has changed.[51]
Result
detects deletion alleles
direct sequencing/reverse dot blot
Test
Used to detect nondeletional alpha-thalassemia mutations.[48][50]
If there are existing genetic test results, do not repeat a genetic test unless there is uncertainty about the existing result, for example, the result is inconsistent with the patient’s clinical presentation or the test methodology has changed.[51]
Result
detect nondeletional alpha-thalassemia mutations
MRI (hepatic or cardiac)
Test
Hepatic iron overload can be assessed by R2 or R2* MRI.[53]
MRI is the gold standard for measurement of hepatic iron concentration.[16]
Cardiac iron loading is assessed by T2* cardiac MRI.[48] Cardiac iron loading is uncommon in nontransfused patients.
Result
hepatic or cardiac iron in patients with iron overload is demonstrated by difference in organ-to-muscle signal intensity
superconducting quantum interference devices (SQUID)
liver biopsy
Test
If iron status is significantly elevated as evident by a serum ferritin >800 nanograms/mL, hepatic iron overload can be assessed by liver biopsy.[52][53]
MRI is preferred to liver biopsy for assessment of iron overload where possible as it has better accuracy and fewer procedural risks. Liver biopsy may be used where assessment of histology is needed.[21]
Result
liver iron ≥5 mg/gram dry weight on liver biopsy indicates need for iron chelation therapy
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