Arterial oxygen tension, haemoglobin F and red cell 2, 3 diphosphoglycerate in sickle cell anaemia patients with digital clubbing.

Eleven (12.4%) out of 89 steady-state homozygous sickle cell patients attending our clinic had digital clubbing. These patients were compared with two groups of age- and sex-matched controls-SS patients without clubbing and apparently healthy HbAA individuals. The patients with clubbing had significantly lower arterial oxygen tension than the SS patients without clubbing and the HbAA controls. The mean (SD) values of PaO2 in the three groups were 64.16 (10.39), 75.66 (15.25) and 93.62 (13.45) mmHg, respectively. Also, the patients with clubbing had significantly higher levels of HbF-7.34 (3.53)% against 4.9 (3.14)%--and higher red cell 2, 3 DPG concentrations--1.59 (0.36) mumol/ml against 1.14 (0.52) mumol/ml--than the SS patients without clubbing. This work shows that severe hypoxaemia with compensatory increases in HbF and red cell 2, 3 DPG levels is a prominent feature in SS patients with clubbing. The predisposing factor(s) to this severe degree of hypoxaemia in the patients with clubbing are still not quite clear.