Target cells in haemoglobinopathies.

A semi-quantitative method of estimating the number of target cells in blood films has been developed. It has been applied to 250 films from normal persons, pregnant women, and patients with a variety of haemoglobinopathies. Allowing for the frequency of target cells found in normal films the results show that such an examination is of value in eliminating or suggesting certain haemoglobinopathies, but not in excluding the majority of the traits.