The detection of hemoglobin variants by isoelectrofocusing using EDTA-collected and filter paper-dried cord blood specimens

A comparative study was conducted aimed at the detection of abnormal hemoglobin conditions (mainly AS, SS, AC, CC, SC, AE, AD, Hb Bart's or γ₄) by isoelectrofocusing of cord blood samples stored as liquid blood and as dried hemoglobin on filter paper. Analyses were made within four to six days after the collection of the samples; storage conditions mimicked those of testing programs using liquid blood samples (as in Georgia) or dried blood filter paper samples (as in several other states). During analysis of hemoglobin solutions extracted from dried blood samples, considerable difficulties were encountered in detecting significant hemoglobinopathies such as SS and SC, whereas even simple abnormalities such as AS, AC, AD, and AE were also often not diagnosed. Detection of the fast-moving variant Hb Bart's or γ₄ was not possible. These results again cause doubt regarding the general use of dried blood filter paper samples in newborn hemoglobin testing programs. Perhaps special precautions - such as speed in analyzing the samples, storage at -20 °C (or perhaps 4 °C) instead of at room temperature, and removal of unstable hemoglobin from the filter paper extract by centrifugation - might eliminate some of the problems that were observed.