Thalassemia minor DF

Discriminant Factor (DF) is a mathematical computation to discriminate Thal minor from Iron Deficiency:

Mentzer:
MCV/RBC =
less than 13: Thal minor
more than 13: Fe def

Shine-Lal:
(MCV)squared X MCH =
less than 1530: Thal minor
more than 1530: Fe def

England-Frazer :
MCV-(Hgb X 5)-RBC- 3.4 =
(-) thal minor
(+) Fe def

The England-Frazer formula is the most often used.

Other notes:

• Hemoglobin is very seldom, if ever, below 95 g/L. If the Hgb is less than 93 g/L it is unlikely the patient has beta thalassemia minor

White cell count and differential - normal

Retics - relative increasePI decreased

Bone marrow - normal to slight erythroid hyperplasia.

Serum iron - normal
TIBC - normal
Ferritin - normal
Bilirubin - slight increase due to intramedullary hemolysis
FEP - normal

Hemoglobin studies:
Hgb A - decreased
Hgb A2 - increased
Hgb F - Sl increase to normal

source
F.A. Rice, ART, CLS March 1, 1996
(link)