Table 1. Classification of hereditary spherocytosisa.

	Carrier	Mild spherocytosis	Moderate spherocytosis	Severe spherocytosisb
Hemoglobin (g/dl)	Normal	11–15	8–12	6–8
Reticulocytes (%)	≤3	3–6	≥6	≥10
Bilirubin (mg/dl)	0–1	1–2	≥2	≥2
Spectrin content (% of normal)	100	80–100	50–80	40–60
Peripheral smear	Normal	Mild spherocytosis	Spherocytosis	Spherocytosis
Osmotic fragility fresh blood	Normal	Normal or slightly increased	Distinctly increased	Distinctly increased
Incubated blood	Slightly increased	Distinctly increased	Distinctly increased	Distinctly increased

^aFrom Eber SW, Armbrust R, Schroter W. Variable clinical severity of hereditary spherocytosis: relation to erythrocytic spectrin concentration, fragility, and autohemolysis. J Pediatr 1990;117:409-416.

^bValues in untransfused patients.