[Hemoglobin anomalies at the university hospital center in Lome, Togo]

Abstract

Togo is a sub-Saharan African nation with a number of public health problems including endemic tropical disease. The country is also located in the Lehmann sickle cell belt characterized by a high incidence of genetic red blood cell disorders. The purpose of this study was to identify the main hemoglobin variants, evaluate their incidence and discuss diagnostic pitfalls. Data on 5604 subjects was compiled from the 3 studies, i.e., a 405-case prospective study conducted in a rheumatology department, a 5028-case retrospective study using electrophoresis and a 171-case transversal study in newborns. Diagnosis of hemoglobinopathy was based on alkaline electrophoresis. Rare hemoglobins were identified in the Biochemistry Laboratory of the Henri Mondor Hospital in Paris, France. Diagnosis of alpha-thalassemia was checked by PCR. The main abnormal hemoglobins were the S and C variants with respective incidence ranges of 15.8 to 16.7% for the AS trait and 12.1 to 15.8% for AC trait. SS sickle cell disease was observed in 1.2 to 2% of subjects and SC sickle disease in 2.3 to 4.2%. Rare hemoglobulinopathies involved the fast hemoglobulin variant, hemoglobin D, and hereditary persistence of hemoglobin F. Alpha-thalassemia was detected in 47% of the 171 newborns studied with a predominance of the heterozygous form (36.8%), followed by the homozygous form (8%). The incidence of alpha gene triplication in the newborns was about 2.4%. Hemoglobin Barts was not a consistent finding in association with diagnosis of alpha-thalassemia since it was present in 15 newborns with normal alpha genotype (8.8%) and absent in 10 newborns with heterozygous alpha genotype (5.9%). This study demonstrates that molecular biology is the best method for the detection of the alpha-globin gene abnormalities.