In conclusion, the present study demonstrates that high reticulocytosis in neonate blood does not bias measurement of enzyme activity in G-6-PD-deficient neonates. In addition, the high prevalence of G-6-PD variants associated with low activity (WHO class II G-6-PD type), in conjunction with mosaicism of X-chromosome inactivation could result in female heterozygous neonates with such genotypes having G-6-PD activity falling either in (low) normal or
deficiency range, and only genotyping would permit detection of heterozygotes carrying these variants among those with G-6-PD normal phenotypes