Hb Electrophoresis in ß-Thal + Iron Deficiency: Example

Normal Hemoglobins have a Heme Moiety plus 4 Globin chains
  • Always  2 α-chains
  • The 2 α-chains pair preferentially with 2 β-chains (HbA)
  • Some α’s (<3%) pair with δ-chains (HbA2) or γ-chains (HbF)
Case #1:  Normal:  Suppose we have:
  • 1,000 Heme moieties (with iron)
  • 2,000 α-chains
  • 2,000 β-chains
  • Various γ-chains and δ-chains
980 of the Hemes join with 1960 α-chains and 1960 β-chains
The other 20 Hemes join with α’s plus δ’s or γ’s
This gives a normal electrophoresis of, say:
  • 98%  HbA
  • 1.5%  HbA2
  • 0.5%  HbF
Case #2:  β-Thalassemia = Deficient number of β-chains:
  • 1,000  Heme moieties (with iron)
  • 2,000  α-chains
  • 1,800  β-chains (decreased)
  • Various γ-chains and δ-chains
900 of the Hemes join with 1,800 α-chains and the 1,800 β-chains
The other 100 Hemes join with the left-over α’s pairing with δ’s and γ’s
This gives an abnormal electrophoresis of, say:
  • 90%  HbA
  • 7%  HbA2
  • 3%  HbF
Case #3:  β-Thalassemia + Iron-Deficiency (i.e. fewer Hemes)
  • 750 Hemes (if Hct drops from 40 to 30)
  • 2,000  α-chains
  • 1,800  β-chains  (decreased due to β-Thal)
  • Various γ-chains and δ-chains
735 of the Hemes join with 1470 α’s and 1470 β’s
The other 15 Hemes join with α’s plus δ’s and γ’s
This now gives a normal electrophoresis:
  • 98%  HbA  [735 out of 750]
  • 1.5%  HbA2
  • 0.5%  HbF
Decreased quantities, but normal percents.
Increase the Hemes, & we’re back to Case #2 (abnormal percents)

Hope this makes sense [???]