Abstract:
Objective: Red cell indices and parameters are used to screen beta-thalassemia trait
(BTT). Different red cell indices and formulae used to discriminate BTT in different
populations show inconsistent results.
Methods: A retrospective study was performed to assess reliability of 11 red cell
indices, parameters and formulae in differentiating BTT from non-BTT in a cohort of
individuals referred for confirmation of BTT.
Results: Of 111 individuals, 79 were females and 32 were males. Of the total, 89
were confirmed to have BTT by Hb A2 quantification. The mean age of the group
was 29.9 ± 19.2 years. The mean Hb concentration, MCV and MCH in BTT group
were 10.45 ± 1.6 g/dL, 62.1 ± 5.4 fl, and 19.7 ± 1.7 pg, respectively. The mean red
cell count in BTT group was 5.3 ± 0.8 × 109
/L while in non BTT group it was 4.7 ±
0.7 × 109
/L. The highest specificity (86.4%) was shown by Sirdah, Sriwastava and
England and Fraser indices, but their sensitivities were 61.8%, 57.3%, and 32.6%. The
lowest number of false positives (n = 3, 13.6%) was shown by Srivastava, Sirdah and
England and Fraser indices. Shine and Lal index showed 100% sensitivity and NPV
and 12 false positives. MCV and MCH showed results similar to Shine and Lal index
with 16 false positives each.
Conclusion: Use of Shine and Lal index in screening programs of BTT is superior to
all the other indices and formulae. To confirm the findings of this study, further studies
are recommended to be carried out in Sri Lanka on different ethnicities.
