Rapid identification of hemoglobin variants by electrospray ionization mass spectrometry

The precise identification of human hemoglobin variants, over 700 human hem oglobin variants are known, is essential for prediction of their clinical a nd genetic significance. A systematic approach to their rapid identificatio n is described. Traditionally this requires protein or DNA characterization which entails lengthy analytical procedures, To overcome these obstacles a rapid approach to variant hemoglobin identification has been developed usi ng conventional phenotypic methods combined with electrospray ionization-ma ss spectrometry (ESI-MS). The latter requires only a small amount of whole blood (10 mul) but in most cases 2 mul would have been sufficient and no pr eanalytical steps, such as separation of red cells or globin chains, are ne cessary. Aged, hemolyzed blood samples can also be analyzed. This approach has been used to positively identify 95% of the variants in over 250 sample s. The remaining 5% in which a variant Was detected by phenotypic technique s were not resolved by mass spectrometry. Ninety-nine different abnormaliti es comprising 36 alpha -chain variants, 59 beta -chain variants (including 2 extensions), and 4 hybrid hemoglobins were identified. These include 15 n ovel variants. The application of ESI-MS described requires approximately 1 h to prepare and analyze each sample and has minimal reagent costs. The tu rnaround time on a single sample can be as little as 2 h. This technique ca n now be considered a useful additional tool for reference laboratories. (C ) 2001 Academic Press.