Abstract:
Sickle cell anemia (SCA) is the commonest severe monogenic disorders of humans. The
disease has been highly characterized in high-income countries but not in sub-Saharan
Africa where SCA is most prevalent. We conducted a retrospective cohort study of all
children 0-13 years admitted from within a defined study area to Kilifi County Hospital
in Kenya over a five-year period. Children were genotyped for SCA retrospectively and
incidence rates calculated with reference to population data. Overall, 576 of 18,873
(3.1%) admissions had SCA of whom the majority (399; 69.3%) were previously
undiagnosed. The incidence of all-cause hospital admission was 57.2/100 person years of
observation (PYO; 95%CI 52.6-62.1) in children with SCA and 3.7/100 PYO (95%CI
3.7-3.8) in those without SCA (IRR 15.3; 95%CI 14.1-16.6). Rates were higher for the
majority of syndromic diagnoses at all ages beyond the neonatal period, being especially
high for severe anemia (hemoglobin <50 g/L; IRR 58.8; 95%CI 50.3-68.7), stroke (IRR
486; 95%CI 68.4-3,450), bacteremia (IRR 23.4; 95%CI 17.4-31.4), and for bone (IRR
607; 95%CI 284-1,300), and joint (IRR 80.9; 95%CI 18.1-362) infections. The use of an
algorithm based on just five clinical features would have identified approximately half of
all SCA cases among hospital-admitted children with a number needed to test to identify
each affected patient of only fourteen. Our study illustrates the clinical epidemiology of
SCA in a malaria-endemic environment without specific interventions. The targeted
testing of hospital-admitted children using the Kilifi Algorithm provides a pragmatic
approach to early diagnosis in high-prevalence countries where newborn screening is
unavailable.