OBJECTIVETo analyze the genotype-phenotype correlations in the Hb Constant Spring (HbCS) carriers, and to investigate the effect of HbCS on hematologic parameters.

METHODSComplete blood cell count and hemoglobin electrophoresis analyses were performed in 125 HbCS cases. The α-and β-thalassemia mutations were determined by reverse dot-blotting and Gap-PCR.

RESULTSThe presence of the SEA deletion or Hb Quong Sze (HbQS) with HbCS leads to HbH-CS disease. There was significant difference between HbH-CS and αCSα/-α, HbH-CS and αCSα/αα in the hematological parameters. The genotype of αCSα/-α or αα/αCSα had slight effect on hematological parameters. When the Hb Constant Spring mutation co-existed with heterozygous β-thalassemia, the hematological characteristics of β-thalassemia was presented. Only 57.6% of carriers with HbCS were detected by hemoglobin electrophoresis.

CONCLUSIONThe cases with co-existence of HbCS trait and other α-thalassemia trait, or β-thalassemia trait, showed variation in their red blood cell parameters. For such compound heterozygotes for HbCS and other α- or β-thalassaemia mutations, which were usually misdiagnosed in clinical screening by hemoglobin electrophoresis, accurate diagnose can be made by molecular diagnosis.