Foetal haemoglobin, erythrocytes containing foetal haemoglobin, and hematological features in congolese patients with sickle cell anaemia

Abstract

High HbF levels and F cells are correlated with reduced morbidity and mortality in sickle cell disease (SCD). This paper was designed to determine the HbF and F cells levels in Congolese sickle cell anemia (SCA) patients in order to determine their impact on the expression of SCD. Population and Method. HbF levels were measured in 89 SCA patients (mean age 11.4 yrs) using a standard HPLC method. F cell quantitation was done in a second group of SCA patients (n = 42, mean age 8.9 yrs) and compared with a control group (n = 47, mean age 5 yrs). F cells were quantified by a cytofluorometric system (MoAb-HbF-FITC; cut off at 0.5%). Results. The mean value of HbF was 7.2% ± 5.0 with heterogeneous distribution, most patients (76%) having HbF < 8%. Mean values of F-cells in SCA patients and control group were 5.4% ± 7.6 (median: 2.19%; range 0,0-30,3%) and 0.5% ± 1.6 (median 0.0, range 0-5.18), respectively. SCA patients with F cells >4.5% developed less painful crisis and had higher percentage of reticulocytes. Conclusion. Congolese SCA patients displayed low levels of HbF and F-cells that contribute to the severity of SCD.

Figure 1

Population distribution of the HbF rate. Patient distribution related to HbF rate displayed a heterogeneous pattern with a predominant group (74%) with HbF% <8. GIobally, only 20/89 (or 22.5%) of patients displayed values higher than 10% of HbF.

Figure 2

Illustration of flow cytometric and KS aspects of F cells values in a SCA patient and a control. HbF expression was, also, analyzed using the Kolmogorov-Smirnov (KS) statistic test (D-value), which allows the objective and accurate identification of small differences in fluorescence intensity. Samples were considered positive when D ≥ 0.15.

Figure 3

% F cells distribution in 42 SCA patients related to age. The mean value was at 5.44 ± 7.6 with a non gaussian pattern even after log-transformation of values (not shown).