The risk of acute events among patients with sickle cell disease in relation to early or late initiation of care at a specialist center: evidence from a retrospective cohort study

Abstract

Background: The greatest disease burden of sickle cell disease occurs early in life. Understanding factors that reduce disease related events in this period is therefore important. Hence, we assessed the impact of early care at a specialist center on the incidence of acute events during the first five years.

Methods: This was a retrospective cohort study among Jamaican children with sickle cell disease. Medical records of patients born January, 2004 to December, 2009, who were registered at the Sickle Cell Unit, a specialist care facility, were abstracted for dates of initiation to care, first occurrence and frequency of the outcomes of interest (vaso-occlusive crises, acute splenic sequestration, acute chest syndrome, and infection). Patients were classified according to whether initiation of care was before (early) or after 5 months of age (late). Using standardized t-tests, χ2 tests, and a multiple-failure survival analysis the rates of acute events between groups were compared.

Results: Of the total study group (n= 290), homozygous sickle cell disease accounted for 97% and 95% of the early (n=113) and late groups (n=177) respectively. The mean age of presentation in the early and late group was 0.2 and 2.3 years (p<0.01), with a mean length of follow-up of 5.2 and 3.2 years respectively (p<0.01). Vaso-occlusive crisis (n=880) and acute chest syndrome (n= 571) together accounted for 91.6% of the total number of events (n=1584). The risk of vaso-occlusive crisis and acute chest syndrome (among patients who presented with these acute events) was significantly higher in the "late" group, by 43% (Incidence rate ratio, (IRR) = 1.43, p<0.001); 95% CI (1.18-1.72) and 40% (IRR=1.40. p=0.002), 95% CI (1.12-1.75) respectively compared to "early" group. There was no difference in risk between groups for acute splenic sequestration and infection among persons presenting with these events.

Conclusion: The risk of acute events in children with sickle cell disease exposed to early care at a specialist care is significantly less. Therefore, widespread screening with rapid referral to a specialist center stands to reduce substantial morbidity in Jamaica and other regions with high prevalence of sickle cell disease.

Keywords: Acute chest syndrome; Acute splenic sequestration; Penicillin prophylaxis; Red blood cell disorder; Sickle cell disease.

Fig. 1

Flow diagram showing the proportion of early or late presenters diagnosed by newborn screening. N represents the number of patients

Fig. 2

Kaplan-Meier survival curves showing incidences of acute events. Kaplan-Meier survival curves showing incidences of Acute Chest Syndrome (a); Vaso-occlusive crisis (b); Acute Splenic Sequestration (c) and Infection (d) in patients born between January 1, 2005 and December 31, 2009 who presented early or late to the Sickle Cell Unit in Jamaica and were followed from time of imitation of care at a specialist center to age 5.5years (N = 290)