The use of Hb as
a parameter to assess potential anaemia is sometimes not possible in the clinical setting where the Hct value is the only means available for assessment of anaemia.
Citrate agar gel electrophoresis demonstrated a variant Hb in all 8 specimens (100%), which migrated between Hb A
and Hb F, as previously described for Hb Austin (Figure 1).1 The HPLC on the 8 specimens revealed a retention time of 0.73 to 0.74 relative to Hb A
, which is also consistent with Hb Austin (Figure 2).
Hb Average RBC Lifespan in Days (n) Hb A
120 Hb S 93 (3) (20) Hb E No Data Hb C 87 (6) (18) Hb D 115 (3) (19) Table 2.
An unintended consequence, however, is the ability of these Hb variant interference-free methods to measure and report Hb [A.sub.1c] values for patients lacking Hb A
In CE-HPLC and electrophoresis assays, Hb [A.sub.1c] can be separated from Hb A
because glycation of the N-terminal valine decreases the positive charge.
Several methods, including the D-10, DiaSTAT, Dimension RxL, DS5, HA8160, and VARIANT II, showed increased scatter when samples containing Hb C or S trait were tested compared with that seen for samples homozygous for Hb A
On acid electrophoresis, the two hemoglobin variants, however, had mobilities identical to Hb A
but not Hb C.
For each test method, results for each group of samples (Hb AA, Hb AC, Hb AS
) were compared with results from the comparative method (CLC 330).
The Bio-Rad Variant (Bio-Rad Laboratories) is an automated cation-exchange HPLC instrument that has been used to quantify Hb [A.sub.2], Hb F, Hb A
, Hb S, and Hb C.
To eliminate suspected carryover when samples containing Hb C trait were analyzed by the A1c 2.2 Plus method, three samples homozygous for Hb A
were analyzed but not reported after each sample containing Hb C trait.
The Variant method poorly resolved Camden from Hb A
and underestimated gHb (Fig.
The Hb [A.sub.2] values measured by a specific method seem similar in Hb D heterozygotes and Hb A