Accuracy of prenatal diagnosis for haemoglobin disorders in the UK: 25 years' experience.

We have reviewed the accuracy of prenatal diagnosis for the thalassaemias and sickle cell disorders performed for UK residents since the service began in 1974. Prenatal diagnosis has been performed in 3254 pregnancies: 517 by fetal blood analysis, 681 by Southern blotting and 2056 by polymerase chain reaction (PCR) methods, the majority using the amplification refractory mutation system (ARMS). The number of homozygotes diagnosed was 808 (24.8%). Twenty-five diagnostic errors have been recorded, ten arising from non-laboratory errors (0.31%) and 15 due to technical problems associated with the diagnostic techniques. The latter group consisted of eight misdiagnoses by globin chain synthesis (1.55%), five by Southern blot analysis (0.73%) and two by PCR methods (0. 10%). The data show that the accuracy of prenatal diagnosis has improved with each development of diagnostic technique, and confirms that prenatal diagnosis of beta-thalassaemia and sickle cell disorders by ARMS-PCR is very accurate and reliable. The overall error rate for prenatal diagnosis by PCR methods in the UK is now 0. 41%. Copyright 2000 John Wiley & Sons, Ltd.