Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Haemoglobin S (HbS) or sickle cell haemoglobin, results from an autosomal recessive mutation to the beta globin gene. Red cells containing HbS have a reduced deformability, under conditions of Hypoxia they form the so-called sickle shape and are easily destroyed resulting in occlusion of the microcurculation and a chronic haemolyitic anaemia. Heterozygotes have sickle cell trait, homozygotes have sickle cell disease. HbS may be found in conjunction with other Haemoglobin mutations and compound heterozygotes may display the features of homozygous disease or be asymptomatic depending on the combination. The screening test will detect the presence of HbS or a form of sickling haemoglobin variant in a sample, it will not distinguish between HbAS (heterozygote) and HbSS (homozgote) or other sickling haemoglobin A/V. All requested will received a haemoglobinopathy screen to confirm the result. The test is used as a quick pre-op screening test in patients with a family history of HbS or if the patient is from a region with a high prevalence of the mutation (Africa, Middle East, Mediterranean and India) as general anaesthesia presents a significant risk to patients with this mutation.
Specimen container paediatric:
EDTA – Purple/Pink top
Specimen container adult :
EDTA- Purple/Pink top
Minimum volume paediatric:
1ml – to allow for follow up haemoglobinopathy screening
Minimum volume adult:
1ml – to allow for follow up haemoglobinopathy screening
Special requirements:
Testing should not be requested on patients who are within 4 month post red cell transfusion as this will impact on validity of results. Testing should not be requested on patients who are less than 6 month old. Suggest request for haemoglobinopathy screen or review of patient newborn sickle screening blood spot result.
Sample stability:
Sample suitable for up to 45 days when stored between 1-10oC.
Transport requirements:
No Special transport requirements
Freq analysis:
Monday-Friday Completed daily within routine hours, Saturday, Sunday and Out of hours completed ad hoc for clinically urgent requests only
Add on test:
All urgent add ons via telephone, phone extension 24766 for protein laboratory or 25819 for RVI haematology must be confirmed via email to the appropriate email address:
[email protected] (internal)
[email protected] (external)
Quality assurance:
Participate in UK NEQAS Abnormal Haemoglobin Scheme
Interpretation:
Positive – Suggest Haemoglobin S present or a form of sickleing haemoglobin variant. Negative – Suggest Haemoglobin S not present.
All results require confirmation via High Performance Liquid Chromatography via a Haemoglobinopathy screen. During routine hours, this will be completed by the Protein laboratory. If confirmation and haemoglobin S quantitation required urgently out of hours this must be discussed with the Biochemistry Biomedical Scientist on shift EXT 24305/24041.
Reference Ranges:
Sickle solubility- reference range not applicable. Results reported as Positive or Negative.
Factors affecting result:
Patient age – Testing not appropriate for patients under 6 month due to intereferance cause by HbF. Please refer to patient’s Newborn screening result if confirmation of sickle status required or request a haemoglobinopathy screen if newborn screening results not available.
Post transfusion – Testing not appropriate if patient is post transfusion. This may give a false negative result. Discuss with laboratory if clinical concern.
Testing should not be completed on clotted sample or haemolysed sample.
A repeat sample will be requested False positive may occur due to abnormal plasma proteins or parenteral nutrition therapy.
Other Info:
All newly identified abnormal haemoglobin variants will have a sickle solubility screen completed to support haemoglobinopathy screening interpretation.