Comparison between PCR– based Single Tube Genotyping of Sickle Cell Disease and Alkaline Haemoglobin Electrophoresis

Abstract

Background: Sickling test and haemoglobin solubility test are screening techniques used to detect the presence of haemoglobin S, but can't identify exact phenotype or genotype. Haemoglobin electrophoresis can determine the phenotype of sickle cell disease but it cannot be performed on infants aged less than 6 months because of the presence of hemoglobin F as the predominant hemoglobin before this age and thus it is not suitable for prenatal and neonatal screening. This study aimed to compare PCR-based single tube genotyping of sickle cell disease with routine alkaline haemoglobin electrophoresis.  Materials and Methods: This is a cross sectional-analytic study conducted at Khartoum state, Sudan in the period from November 2014 to March 2015. The total number of study subjects was 70, 35 of them with sickle cell anaemia (Hb S/S), 15 sickle cell trait (Hb A/S), and 20 healthy volunteers (Hb A/A). Blood samples were collected in EDTA blood tubes and genomic DNA was extracted from leucocytes by salting out method. Allele specific polymerase chain reaction (PCR) was used for genotyping of all samples. Alkaline haemoglobin electrophoresis was also performed on all subjects to confirm the phenotypes and the findings were compared with genotyping results. Results: Using alkaline Hb electrophoresis, 33(94.3%) out of 35 patients with provisional diagnosis of sickle cell anaemia were found to be S/S and 2(5.7%) were A/S; using PCR all the 35 patients were found to be S/S; the two patients who their phenotype was A/S while by PCR their genotype was S/S were found to have a history of recent allogenic blood transfusion. The results of Hb electrophoresis and PCR were in full agreement for both sickle cell trait individuals (A/S), and the healthy controls (A/A). Conclusion: Diagnostic accuracy of PCR based single tube genotyping of SCD is superior to routine alkaline haemoglobin electrophoresis particularly in situations of recent allogeneic blood transfusion and prenatal and neonatal screening.