CLINICAL NEWS
in a Different Vein
Research from ASH’s newest peer-reviewed
journal, Blood Advances
Examining Hemoglobin Variants and Geographic
Variability of Sickle Cell Trait and Sickle Cell Disease
in Sub-Saharan Africa
Results from the prospective Uganda
Sickle Surveillance Study (US3),
which was created through a partnership among the Uganda Ministry
of Health, Makerere University, and
Cincinnati Children’s Hospital Medical Center, estimated that the overall
national prevalence was 13.3 percent
for sickle cell trait (SCT) and 0.7
percent for sickle cell disease (SCD).
However, there was considerable geographic variability in prevalence and
in hemoglobin variants among the
study population, which included infants and children from all 10 regions
and 112 districts of Uganda.
In an analysis of US3 data published in Blood Advances, Beverly A.
Schaefer, MD, and authors sought
to define the clinical importance of
these hemoglobin variants, with a
goal of creating algorithms that could
assist in the development of hemoglobinopathy screening programs in
sub-Saharan Africa.
“As newborn screening efforts for
SCD increase in sub-Saharan Africa,
recognition and correct identification
of common hemoglobin variants,
particularly those that may be mistaken for Hb S, will reduce repetitive
testing and improve testing accuracy,”
Dr. Schaefer and authors wrote.
“Given the migratory history and
tribal structure of Uganda’s population, we hypothesized that individual
hemoglobin variants would differ
across the country but would likely
be clustered by region.”
Dr. Schaefer and authors reanalyzed dried blood samples that had
undergone hemoglobin isoelectric
focusing (IEF) through the US3 study
to identify and locate variant samples.
The country-wide prevalence of
hemoglobin variants was 0.5 percent,
varying from 0.1 percent of samples
collected in the Southwestern region
to 1.8 percent in the West Nile region
(FIGURE). Variants were detected in 94
of 112 districts, and 458 samples were
identified as a hemoglobin variant.
After the study was completed, a
total of 190 dried blood samples with
variant hemoglobin bands on IEF
ASHClinicalNews.org
were located, retrieved, and evaluated
using DNA-based techniques.
The five most common hemoglobin variants in the US3 study, which
appeared in 83 percent of the tested
dried blood samples, exhibited the
following IEF patterns:
• 2 alpha globin variants (Hb
Stanleyville-II, Asn78Lys and Hb
G-Pest, Asp74Asn)
• 1 beta globin variant (Hb
O-Arab, Glu121Lys)
• 2 fusion globin variants (Hb
P-Nilotic, β31-δ50 and Hb Kenya,
Aγ81Leu-β86Ala)
Identification and geospatial mapping
of variants confirmed the authors’
hypothesis