genes G C A T T A C G G C A T Article Hemoglobin A 2 and Heterogeneous Diagnostic Relevance Observed in Eight New Variants of the Delta Globin Gene Noraesah Mahmud 1,2 , Massimo Maffei 1, * , Massimo Mogni 1 , Gian Luca Forni 3 , Valeria Maria Pinto 3 , Giuseppina Barberio 4 , Silvana Ungari 5 , Antonella Maffè 5 , Cristina Curcio 6 , Francesco Zanolli 7 , Raffaella Paventa 8 , Mariarosa Carta 9 , Alberta Caleffi 10 , Mariella Mercadanti 10 , Sauro Maoggi 11 , Giovanni Ivaldi 12 and Domenico Coviello 1   Citation: Mahmud, N.; Maffei, M.; Mogni, M.; Forni, G.L.; Pinto, V.M.; Barberio, G.; Ungari, S.; Maffè, A.; Curcio, C.; Zanolli, F.; et al. Hemoglobin A 2 and Heterogeneous Diagnostic Relevance Observed in Eight New Variants of the Delta Globin Gene. Genes 2021, 12, 1821. https://doi.org/10.3390/genes12111821 Academic Editor: Gael Roue Received: 22 October 2021 Accepted: 17 November 2021 Published: 19 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Laboratorio Genetica Umana, IRCCS Istituto Giannina Gaslini, 16147 Genova, Italy; noraesah.mahmud@moh.gov.my (N.M.); massimomogni@gaslini.org (M.M.); domenicocoviello@gaslini.org (D.C.) 2 Department of Pathology, Hospital Kuala Lumpur, Kuala Lumpur 50586, Malaysia 3 Centro Microcitemia e Anemie Congenite, Ospedali Galliera, 16128 Genova, Italy; gianluca.forni@galliera.it (G.L.F.); valeria.pinto@galliera.it (V.M.P.) 4 Medicina di Laboratorio, Azienda ULSS 2 Marca Trevigiana, 31100 Treviso, Italy; giuseppina.barberio@aulss2.veneto.it 5 Genetica e Biologia Molecolare ASO S. Croce e Carle, 12100 Cuneo, Italy; ungari.s@ospedale.cuneo.it (S.U.); maffe.a@ospedale.cuneo.it (A.M.) 6 Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, 20122 Milano, Italy; cristina.curcio@policlinico.mi.it 7 Formerly, Servizio di Immunoematologia e Medicina Trasfusionale, A.O. Santa Maria degli Angeli, 33170 Pordenone, Italy; francesco.zanolli@hotmail.it 8 Formerly Laboratorio Analisi, ASL AT, 14100 Asti, Italy; raffaellapaventa@gmail.com 9 Medicina di Laboratorio, Ospedale S. Bortolo, AULSS 8 Berica, 36100 Vicenza, Italy; mariarosa.carta@aulss8.veneto.it 10 U.O. Diagnostica Ematochimica, Azienda Ospedaliero-Universitaria, 43126 Parma, Italy; acaleffi@ao.pr.it (A.C.); mercandrea1953@libero.it (M.M.) 11 Sebia-Italia S.r.l., 50012 Bagno a Ripoli, Italy; sauro.maoggi@sebia.it 12 Formerly, Laboratorio Genetica Umana, Galliera Hospital, 16128 Genova, Italy; g.ivaldi@live.it * Correspondence: massimomaffei@gaslini.org Abstract: Background: Hemoglobin A (Hb A) (α 2 β 2 ) in the normal adult subject constitutes 96–98% of hemoglobin, and Hb F is normally less than 1%, while for hemoglobin A 2 (Hb A 2 )(α 2 δ 2 ), the normal reference values are between 2.0 and 3.3%. It is important to evaluate the presence of possible delta gene mutations in a population at high risk for globin gene defects in order to correctly diagnose the β-thalassemia carrier. Methods: The most used methods for the quantification of Hb A 2 are based on automated high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). In particular Hb analyses were performed by HPLC on three dedicated devices. DNA analyses were performed according to local standard protocols. Results: Here, we described eight new δ-globin gene variants discovered and characterized in some laboratories in Northern Italy in recent years. These new variants were added to the many already known Hb A 2 variants that were found with an estimated frequency of about 1–2% during the screening tests in our laboratories. Conclusions: The knowledge recognition of the delta variant on Hb analysis and accurate molecular characterization is crucial to provide an accurate definitive thalassemia diagnosis, particularly in young subjects who would like to ask for a prenatal diagnosis or preimplantation genetic diagnosis. Keywords: δ-globin gene; δ-globin gene variant; Hb A 2 -variant; β-thalassemia; Hb-variants 1. Introduction Adult hemoglobin (Hb A) (α 2 β 2 ) accounts for 96–98% of all functioning hemoglobin in adult life. Fetal hemoglobin (Hb F) (α 2 γ 2 ) is prevalent in fetal life, but decreases after Genes 2021, 12, 1821. https://doi.org/10.3390/genes12111821 https://www.mdpi.com/journal/genes