The mean HbA2 value for a normal individual was
2.373% and the value ranged from 1–3.5% with a
standard deviation (SD) of 0.49%. The 95% confidence
interval (CI) was 2.32–2.42% (mean 2.377SD 0.052).
The mean HbA2 value for a b-thalassaemia carrier was
4.163% and the value ranged from 3.6–4.8% with an SD
of 0.365%. The 95% CI was 3.98–4.34% (mean
4.167SD 0.179).
b-Thalassaemia Carrier Detection by ELISA 23
The two cases in which HbA2 values were 410 and
electrophoresis showed the presence of hemoglobin E,
the HbA2 values were 2% and 1.9%. This finding shows
the more specific nature of the ELISA, i.e., the
monospecific nature of the assay to HbA2. This could
be a negative aspect of the ELISA, by missing out on the
presence of some variant hemoglobin that may be
present in the sample.
HbA2 was estimated by ELISA and microcolumn
chromatography in 350 samples enrolled in this study.
The values obtained by both the methods compared well
with a correlation coefficient of 0.89 (n 1⁄4 350, Po0.001)
(Figs. 1 and 2) (4).
The ELISA values were on an average 3.9% lower
than the values obtained by microcolumn chromato-
graphy.