Table 1.

Hemoglobin defects in homozygotes for thalassemia and related disorders

State	Anemia	HbA	HbA2	HbF
Normal	None	Normal	Normal	Normal
β+ thalassemia	Severe	Decreased	Normal	Increased*
β0 thalassemia	Severe	Absent	Normal	Increased*
δ-β thalassemia	Mild	Absent	Absent	Increased†
HPFH	None	Absent	Absent	Increased‡
Corfu	Mild	Decreased	Absent	Increased‡

Severe anemia is usually defined as having hemoglobin levels below 70 g/L and requires frequent transfusions.

^*Slightly increased over normal (5%-10% of total normal Hb levels).

^†Moderately increased over normal (10%-30% of total normal Hb).

^‡Markedly increased, that is, almost completely compensatory (85%-100% of total normal Hb).