First-generation assay epitopes typically span amino acids 4 to 10 of the Hb [beta] chain, (7) encompassing the altered amino acid at position 6 present in Hb S and Hb C
(5), (15) The ADA states that Hb [A.sub.1c] can be used to assess glycemic control in patients with Hb S trait; (16) other groups have expanded this recommendation to include Hb C
and Hb D trait.
With alkaline agarose gel testing, some common Hb variants comigrate, such as Hb C
, Hb E, Hb A2 & Hb O-Arab and Hb S, Hb D and Hb G.
The electrophoretic migration of Hb C
, Hb E, Hb A2, and Hb O is similar at alkaline pH.
Analysis by IEF showed the presence of Hb S and another Hb migrating near the position for Hb C
. An HPLC analysis revealed the following: Hb A, <I% (RI, >94%); Hb [A.sub.2],3.5% (RI, 2.0%-3.8%); Hb F, 5.9% (RI, <2.0%); Hb S, 42.1% (RI, none); and Hb Other, 47.5% (RI, none).
On the other hand, the following variants were not detectable with MS: Hb C
, D, E, E-Saskatoon, O-Arab, Lepore-Boston -Washington, and Schlierbach.
Whole blood samples from individuals homozygous for Hb A (n = 73) and heterozygous for Hb C
or S (n = 46 and 76, respectively) were collected in EDTA-containing tubes.
As reported previously (23), Hb O-Arab and Hb C
had statistically different retention times (P <0.001), whereas the %Hb values were not statistically different (P = 0.84).
Whole blood samples from individuals homozygous for Hb A (n = 43) and heterozygous for Hb C
or S (n = 43 and 61, respectively) were collected in EDTA tubes.
One comparison (5) of CIEF with cation-exchange chromatography for the qualitative and quantitative analysis of Hb variants found that quantitative data between the two methods were highly correlated and that CIEF gave slightly better resolution of the unusual variants Hb C
Harlem and Hb D Punjab.
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
It previously has been shown that the presence of Hb C
or S trait, both of which have substitutions at position six of the [beta] chain, can affect the accuracy of some immunoassay results (8).