Peripheral blood (PB) samples were collected to determine the hematological parameters by using a Sysmex XN5000 automated hematology analyzer (Sysmex Corporation, Kobe, Japan). Hb quantification was performed by automated capillary electrophoresis system (CE) (Sebia Capillarys 2, France). The data are shown in Additional file 1: Table S1. All subjects provided written informed consent.

The common 3 types of α-thalassemia mutations [− α3.7 (rightward), − α4.2 (leftward), –SEA (Southeast Asian), Hb Constant Spring (Hb CS or HBA2: c.427T > C), Hb Quong Sze (Hb QS or HBA2: c.377T > C) and Hb Westmead or HBA2: c.369C > G] and 17 types of β-thalassemia mutations [codons 41/42 (–TTCT) (HBB: c.126_127delCTTT), IVS-II-654 (C > T) (HBB: c.316-197C > T) –28 (A > G) (HBB: c.-78A > G), codons 71/72 (+ A) (HBB: c.216_217insA), codon 17 (AAG > TAG) (HBB: c.52A > T), codon 26 (GAG > AAG) (Hb E or HBB: c.79G > A), codon 31 (–C) (HBB: c.94delC), codons 27/28 (+ C) (HBB: c.84_85insC), IVS-I-1 (G > T) (HBB: c.92 + 1(G > T), codon 43 (GAG > TAG) (HBB: c.130G > T), − 32 (C > A) (HBB: c.-82 > A), − 29 (A > G) (HBB: c.-79A > G), − 30 (T > C) (HBB: c.-80T > C), codons 14/15 (+ G) (HBB: c.45_46insG), Cap + 40–43 (–AAACA) (HBB: c.-11_-8delAAACA), initiation codon (ATG > AGG) (HBB: c.2T > G) and IVS-I-5 (G > C) (HBB: c.92 + 5G > C)] in southern China were detected by using suspension array system as previously reported [4].

Sanger sequencing was performed to detect the mutation in HBA1 (MIM 141800), HBA2, HBB (MIM 141900) and HBG (MIM 142200) genes (PCR primers were as follows: HBA1: forward primer 5′-TGGAGGGTGGAGACGTCCTG-3′; reverse primer 5′-TCCATCCCCTCCTCCCGCCCCTGCCTTTTC-3′. HBA2: forward primer 5′-TGGAGGGTGGAGACGTCCTG-3′; reverse primer 5′-CCATTGTTGGCACATTCCGG-3′; HBB: HBBE1 forward primer 5′-CCAATCTACTCCCAGGAGCAG-3′; reverse primer 5′-TGAGGTTGTCCAGGTGAGC-3′; HBBE2 forward primer 5′-GATCTGTCCACTCCTGATGC-3′; reverse primer 5′-GGTAGCTGGATTGTAGCTGC-3′; HBBE3 forward primer 5′-TTCTGGGTTAAGGCAATAGCAA-3′; reverse primer 5′-AGGGGCTGTTGCCAATGTGC-3′; HBG1: forward primer 5′-GGCTACTTCATAGGCAGAGT-3′, reverse primer 5′-TACCTTCCCAGGGTTTCTCC-3′; HBG2: forward primer 5′-AGCCGCCTAACACTTTGAGCA-3′; reverse primer 5′-TACCTTCCCAGGGTTTCTCC-3′).