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Test ID: Sickle Test
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Sickle Cell Solubility Test
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Useful For
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Screening test used for detection of hemoglobin S; an abnormal Beta chain variant hemoglobin causing sickling disorder. Positive sickling test occurs in sickle cell trait (heterozygous for HbS) and in sickle cell disease includings sickle cell anaemia (homozygousity for Hb S) and cases with coinheritance of HbS and another Beta chain variant (double heterozygosity).
Note: Quantification of hemoglobin S is done by other hemoglobinopathies testing methods (i.e: HPLC,Capillary electrophoresis)
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Method name and description
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SICKLEDEX method: A strong reducing agent reduces the hemoglobin which becomes insoluble in the concentrated phosphate buffer and forms a cloudy turbid suspension.
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Reporting name
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Sickle Cell Solubility Test
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Clinical information
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Haemoglobin S, has a glutamic acid to valine substitution at position 6 of the Beta chain. Hemoglobin S is freely soluble when fully oxygenated; on deoxygenation, its solubility is reduced and polymerization of the abnormal hemoglobin occurs. The polymerized Hb will precipitate in the red blood cells causing rigid, deformed red cells leading to hemolysis, blockage of blood flow and consequent tissue infarction. Homozygous hemoglobin S (sickle cell anaemia) is a serious chronic hemolytic anemia most commonly found in those of African or Middle Eastern descent. Hemoglobin S trait generally does not have any clinical implications.
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Specimen type / Specimen volume / Specimen container
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Whole blood.
Container/Tube: EDTA
Specimen Volume: 2 ml (may be part of CBC).
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Collection instructions / Special Precautions / Timing of collection
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Specimens must be analyzed within 48 hours of collection to avoid hemolysis of the specimen.
Do not centrifuge.
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Relevant clinical information to be provided
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Patient/family history of sickle cell disease, other hemoglobinopathies.
Recent history of blood transfusion.
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Storage and transport instructions
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Ambient / Refrigerated. Specimen should not expose to extremely hot or cold weather, as this will impact the specimen integrity.
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Specimen Rejection Criteria
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Insufficient quantity of blood (<1ml in macrotubes & <0.5ml in microtubes).
Errors in patient identification.
Delayed (old) specimen.
Clotted specimen/hemolyzed sample.
Wrong/unlabeled collection container.
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Biological reference intervals and clinical decision values
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Factors affecting test performance and result interpretation
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False positive result may occur in patients with erythrocytosis, hyperglobulinemia, extreme leukocytosis or hyperlipidemia.
Patients with severe anemia (< 15 % hematocrit) may give false positive or false negative results.
False negative results may be encountered in newborn/infants (under the age of 6 months) with elevated levels of hemoglobin F.
Sickling test result could be modified by recent blood transfusion.
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Turnaround time / Days and times test performed / Specimen retention time
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2 working days
Test is performed daily
Specimen is retained for 3 days at 2-8ºC.
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