Abstract: Objective · To investigate the rare variant types of abnormal -α3.7 deletion band samples detected by commercial kits commonly used in thalassemia, and analyze their blood type phenotype, so as to provide reference for clinical consultation. Methods · Peripheral blood samples of 4 238 patients from June 2016 to September 2019 in Ruijin Hospital, Shanghai Jiao Tong University School of Medicine were collected for routine blood analysis. DNA was extracted from whole blood, and the common mutation genes of thalassemia were detected by gap-polymerase chain reaction (Gap-PCR) and reverse dot blot (RDB). Gap-PCR and Sanger sequencing were used to detect rare mutations of α-thalassemia. Results · A total of 109 cases of -α3.7 deletion band were detected by routine genetic testing for thalassemia, among which 15 cases had abnormal -α3.7 deletion band. Gap-PCR and Sanger sequencing showed that 14 cases were confirmed to contain Hong Kong αα (HKαα) gene and 1 case was NG_000006.1:g.34569_38382 del 3 812 bp rare deletion. The misdiagnosis rate of abnormal -α3.7 deletion bands by routine Gap-PCR test for thalassemia was 13.76%. Conclusion · Patients with abnormal -α3.7 deletion bands should be detected for further confirmation by testing rare type of α-thalassemia, which will help provide more accurate genetic diagnosis results and genetic counseling.

Key words: α-thalassemia, Hong Kong αα gene, rare type, gene variant