Haemoglobinopathy Screen

Clinical background:

Haemoglobinopathy screening may be required in the following scenarios: 

1. To confirm a provisional clinical diagnosis, such as sickle cell disease (SCD) or β thalassaemia major
2. To explain a haematological abnormality, such as anaemia or microcytosis
3. To identify an abnormality in the presymptomatic phase
4. To identify foetuses at risk of significant haemoglobinopathies and offer the parents informed choice
5. To permit genetic counselling of prospective parents
6. To identify the presence of sickle cell haemoglobin preoperatively

Haemoglobinopathies are a heterogeneous group of more than 1,000 mutations, which are categorised into 2 main groups:

• Haemoglobin variants which arise from an alteration in the globin protein structure.
• Thalassaemias which arise from inadequate production of structurally normal globin. 

Specimen container paediatric:

EDTA – Purple/Pink top

Specimen container adult:

EDTA – Purple/Pink top

Minimum volume paediatric:

1ml of EDTA whole blood sample

Minimum volume adult:

1ml of EDTA whole blood sample

Sample Stability:

7 days for samples stored at 4^oC

Transport requirements:

• Newcastle Hospitals patient and catchment area requests
  • Samples should be sent ambient and within 24 hours of sample being taken to allow completion of full blood count required for interpretation of haemoglobinopathy screen.
• External hospital patient requests
  • Samples should be sent ambient within 7 days of sample being taken ensure these have been stored at 4^oC prior to sending to reduce impact of degradation on sample results.

Freq Analysis:

Monday-Friday completed daily within routine hours 08:30-17:00

Saturday, Sunday and Out of hours completed ad hoc for clinically urgent HbS quantitation requests only

Add on test:

• All urgent add ons via telephone, 0191 28 24718 for protein laboratory or 0191 28 5819 for RVI haematology and must be confirmed via email to the appropriate email address:
  • [email protected] (internal)
  • [email protected] (external)
• Add on can only be completed on patients who have had a valid and available full blood count sample (EDTA whole blood sample)

Quality assurance:

Laboratory participates in the UKNEQAS Variant Haemoglobins EQA Scheme. The assay is UKAS accredited.

Interpretation:

Patient results are interpreted using the results of the haemoglobinopathy screen and the results of the patients full blood count. Any variant haemoglobin detected is confirmed by three technologies to assess identification prior to interpretation of results.

The reports are guided by the advice provided by BSH guidelines and the antenatal screening handbook.

The laboratory is able to identify clinically significant variant haemoglobins and thalassaemia status’s as stated in the guidelines. Any further advice on interpretation should be discussed with the protein laboratory team or clinical haematology. An interprative report is provided with each patient result.

Reference ranges:

• Hb F <1.1%
• Hb A₂ 2.2 – 3.3%

Factors Affecting Result:

• Red cell transfusion – If a patient has had a red cell transfusion within the previous 4 months of the sample being taken this will impact on the validity of the result, testing will be rejected if presence of transfused blood confirmed. To assess haemoglobinopathy screening results, the patient should be tested 4 month after red cell transfusion unless they are a know Sickle Disease patient requiring assessment of HbS quantitation or beta thalassaemia major patient.
• Age – Patients age can impact on result. For patients who are less than 6 months old we do not recommend completion of a haemoglobinopathy screen and recommend referral to the patients newborn sickle screening to assess risk of clinically significant haemoglobinopathy/thalassaemia status. For patients between 6 months and 13 years old we are unable to assess for presence of non-clinically significant forms of thalassaemia and recommend re-testing at 13 years old if clinical concern and assessment required.

Other info:

• All haemoglobinopathy screening completed for antenatal screening must have an accurate and completed family origin questionnaire provided – this is required for accurate interpretation of patient results.
• All samples tested for haemoglobinopathy screening must pass sample acceptance policy, the patient form and sample must match for the patients first name, surname, date of birth and medical record number either (NHS number or hospital number). Any samples which fail the acceptance policy will be rejected.
• All external hospital requests must have an accompanying full blood count result completed on the sample sent, any which do not have an appropriate full blood count available will be rejected.