4. Discussion
In routine laboratories, the detection of “nondeletion” alpha globin
chain variants in populationswith specificmutation spectrumismainly
performed using traditional well-established PCR-based methods.
These methods, however, target a specific mutation each time and
represent a time-consuming strategy in most populations [7]. More
advantageous in terms of time-saving and costs, especially, when
genotyping samples with a large spectrum of globin gene mutations,
are methods locating or excluding nucleotide variations by evaluating
the melting behaviour of selected PCR amplicons within a gene region.
These methods, however, do not provide a definitive diagnosis, and all
samples must be characterized using another appropriate method to
specify the nucleotide variation [8].
Here,we present a simple, less laborious and cost-effective genotyping
platform for identifying 13 known “nondeletion” alpha globin gene
mutations using as tools PCR and PEXT reaction combinedwith dipstick
assay (biosensor). The method comprises PCR amplification of a single
1087 bp fragment for each HBA1 and HBA2 gene using any conventional
thermal cycler; multiplex PEXT reaction of few (10) cycles, using
unpurified amplification product as a template, to incorporate biotin
into extended allele-specific primers and, finally, visual detection of
the reaction products within minutes by the dipstick biosensor. The
genotype is simply assigned by observing each pair of spots. For any
particular mutation, a normal (wild-type) individual will produce red
colour at the left spot only, whereas a case that is homozygous for a
mutation will produce colour only at the right spot of the pair. Both
spots will be red if the sample is heterozygous for the mutation. The
entire protocol of the proposedmethod including PCR, primer extension
reaction and the dipstick assay takes about 2 h.