The haematology of steady state homozygous sickle cell disease: interrelationships between haematological indices.

The interrelationships between steady state haematological variables in 825 patients with homozygous sickle cell (SS) disease have been examined. On simple correlation coefficient analysis HbA2 correlated negatively with both HbF and MCV, red cell count (RBC) correlated positively with total haemoglobin and negatively with MCV and reticulocytes, and MCV correlated positively with reticulocytes. Less consistent were positive correlations between HbA2 and RBC, between HbF and both MCV and haemoglobin, between MCHC and MCV, and a negative relationship between haemoglobin and reticulocyte count. Partial correlation coefficient analysis clarified some of these relationships. In principal component analysis, the first component weighted positively on Hb and RBC and negatively on reticulocytes and possibly reflected the haemolytic rate. The second component weighted positively on HbF and MCV and negatively on HbA2 and may be related to alpha thalassaemia status. The third component weighted almost exclusively on MCHC and may relate to the degree of intracellular polymerization of HbS. These three components accounted for approximately 75% of the total variation in the haematological data.