Diagnostics

Hemoglobin D (Hb D-Punjab)

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Method:
Anticoagulant:
Recommendation:

Method:

Blood Count
Anticoagulant:

EDTA*
Recommendation:

obligatory

Method:

Hemoglobin Differentiation
Anticoagulant:

EDTA*
Recommendation:

obligatory

Method:

Iron Status
Anticoagulant:

Serum**
Recommendation:

Dep. on Blood Count

Method:

Molecular genetics
Anticoagulant:

EDTA***
Recommendation:

once

^{*3 ml EDTA blood (blood count tube), **7.5 ml serum, ***7.5 ml EDTA blood (extra tube)}

Overview
Diagnostics

Hb D-Punjab: Overview

Hemoglobin D-Punjab (Hb D-Punjab or Hb D-Los Angeles) is caused by an amino acid exchange of amino acid 121 of the β-globin chain from glutamate to glutamine (HBB:c.364G>C, p.Glu122Gln, HbVar-ID 509) and occurs frequently in Punjab with a prevalence of 2 - 3%. Hb D-Punjab is of clinical importance especially in combination with Hb S and its differentiation from other, clinically less important Hb D variants is therefore of diagnostic importance. Compound heterozygosity for Hb D-Punjab and Hb S results in a sickle cell disease, which is, however, less severe than other forms such as homozygous HbS.

Hb D-Punjab: Diagnosis

Diagnosis or exclusion of the presence of Hb D-Punjab is made by a combination of blood count, hemoglobin separation, and molecular genetic testing in the case of abnormal findings to confirm the diagnosis and distinguish it from other Hb D variants.

Carriers of Hb D-Punjab do not show any abnormalities in the blood count. In individual cases of HbD-Punjab homozygosity, mild hemolytic anemia (Hb approximately 10 g/dL to normal) with mild hypochromia and erythrocytosis may occur; reticulocytes may be slightly elevated.

Patients with combined Hb D-Punjab and Hb S typically have a hemoglobin concentration of 5-10 g/dL and reticulocytosis of 5-20%; macrocytosis of up to 110-120 fl often occurs.

Iron status is normal in Hb D-Punjab carriers; in the homozygous state, ferritin may be elevated due to iron overload from hemolysis.

Heterozygous carriers of Hb D-Punjab show an Hb D fraction slightly below 50% in addition to Hb A and Hb A2. Concurrent α-thalassemia decreases the Hb D fraction. Clinically less relevant forms of Hb D other than Hb D-Punjab often migrate similarly in hemoglobin differentiation, so the presence of Hb D-Punjab must be confirmed unequivocally by a second method.

Sequencing of the β-globin gene and detection of the underlying mutation HBB:c.364G>C p.Glu122Gln (HbVar ID 509) confirms Hb D-Punjab and is necessary to make a definitive diagnosis. If no Hb A and predominantly Hb D is detected in the hemoglobin differentiation (>80%), a blood count and molecular genetic deletion analyses using MLPA are performed to distinguish homozygous Hb D from combined heterozygous Hb D and β-thalassemia.

Bain BJ. Haemoglobinopathy Diagnosis. Wiley-Blackwell 2020;3. Edition.

Thomas L 2022 Labor und Diagnose. www.labor-und-diagnose-2020.de. Ausgabe 30.06.2022.

Status: April 2024

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