The steady state haematological characteristics observed in 1071 patients with homozygous sickle cell (SS) disease aged 5–66 years are presented.

Cross sectional studies indicated that HbA₂ levels were consistently higher in males but no age related change was apparent. Fetal haemoglobin levels were consistently higher in females and fell significantly in males between the 5–9 and 10–14 year age groups. Total haemoglobin was significantly higher in females before age 15 and higher in males after 20 years, a dramatic age related rise occurring in males between the 10–14 and 25–29 year age groups, and a fall in patients aged 40 years and over. The mean cell volume was consistently greater in females after 15 years and a marked age related rise occurred in both sexes between the 5–9 and 25–29 year age groups. Counts of irreversibly sickled cells were consistently higher in males. Reticulocytes fell significantly with age, while platelets and total bilirubin fell significantly after the age of 15 years.

Longitudinal studies confirmed the increase in total haemoglobin levels in males over the ages 10–14 years, and a significant fall in males after the age of 30 years. Such studies also confirmed the fall in HbF in males aged 5–14 years, the increase in MCV in both sexes aged 5–29 years, and the fall in platelet counts in both sexes over the age of 20 years.

These observations provide ‘normal’values for patients seen elsewhere and also contribute to an understanding of factors determining the haemoglobin indices in SS disease.