Background: Hydroxyurea (HU) treatment for Sickle cell anemia (SCA) and Sickle beta thalassemia (Sβ-Thal) increases Hgb F level and prevent the symptoms of those diseases which are caused due to Hgb S polymerization. RBCs containing above 20% Hgb F called Fetal Cells (F cells) can inhibit the polymerization. One of the methods to determine the efficacy of HU treatment is measurement of Hgb F percentage in the peripheral blood using HPLC. This method is the acceptable method for monitoring these patients. Since Hgb F is not homogenously distributed among RBCs, HPLC results analysis are not specific and don't provide sufficient information regarding treatment success.
Aim: To examine whether calculating F cells using FACS method instead of Hgb F analyzed by HPLC is better for understanding HU treatment efficiency. Compare the differences between patients treated by HU compared to untreated patients.
Methods: 45 SCA and Sβ-Thal patients aged 2-50 years, (34 patients treated by HU and 11 patients untreated), were examined for F cells presence using FACS based on a combination of two antibodies. The first directed against Hgb F while the second is specific for carbonic anhydrase (CA). Blood samples were also tested for CBC, Reticulocyte count, HPLC and microscopic observation.
Results: Statistically significant differences were found between the two groups in MCV, MCH and Chr (p<0.01). Significantly higher levels of Hgb F and F cells in HU treated patients were observed and also less pathological RBCs morphology. There was a strong positive correlation (R2=0.85) between Hgb F calculated by HPLC and F cells calculated by FACS. Calculation of Hgb F per F cells was performed.
Conclusions: F cells calculation by FACS is required as an additional method for routine assessment of SCA patients treated by HU. Implementation of FACS for F cells examination can provide the physicians accurate information, matching of therapeutic regime for each patient and predicting the disease progress.