Neonatal screening for haemoglobin variants using filter paper-dried blood specimens.

Neonatal screening for haemoglobinopathies utilizing cord blood samples is well established, although it has a high miss rate and has the inherent problem of possible misdiagnosis from maternal contamination of the sample. The use of dried Guthrie card samples which are taken at six days of age avoids these problems and has the advantage of using an established system of sample collection. Controversy exists as to the method of choice for analysis of dried samples, this study of 2406 samples found that Iso-electric focusing (IEF) analysis of dried specimens gives excellent correlation when compared with cellulose acetate/citrate agar electrophoresis of liquid cord blood samples. The IEF results were clear and relatively simple to interpret even when the samples had been stored at room temperature for 4 weeks. The commercial enzyme linked immunosorbent assay (ELISA) screening test JOSHUA reliably determines the presence or absence of haemoglobin S in dried specimens. It could therefore be used as a relatively cheap and simple method for the confirmation of sickle cell trait in neonatal screening programmes based on dried specimens.