Majority of newborns with sickle cell disease survived to adulthood
SAN FRANCISCO — Approximately 91% of newborns with sickle cell disease survived to age 25 years, although the mortality rate accelerated thereafter, according to study results presented at the ASH Annual Meeting and Exposition.
Low baseline hemoglobin also was associated with early mortality, results showed.
Previous estimates of sickle cell disease survival were conducted in the 1980s, Timothy McCavit, MD, MS, assistant professor of pediatrics at the University of Texas Southwestern Medical Center, said during a press briefing. One of these studies, “The Cooperative Study of Sickle Cell Disease,” estimated an average survival to age 44 years for men and 48 years for women with sickle cell anemia.
“Inherent in these studies were significant limitations,” McCavit said. “These were studies which [may have] … involved [a] consenting … group of patients and therefore likely excluded patients who were unlikely to be identified or enrolled. There was also survival bias; they enrolled adults, and so by definition there was a bias toward enhanced survival in those estimates. More recently, studies of survival have estimated somewhat decreased survival from these estimates in adults, and that’s really what has driven us to look at a newborn inception cohort.”
McCavit and colleagues evaluated data from 1,214 patients who were enrolled in the Dallas Newborn Cohort after they were identified as having sickle cell disease through newborn screening (49.2% female). The mean age and mean follow-up of the cohort was 13.2 years (range, 0.1-30).
A majority of the patients had the sickle cell anemia genotype (60.5%), whereas 30.6% had sickle-hemoglobin C disease, 6.8% had beta-positive thalassemia and 2.1% had beta-zero thalassemia.
At the time of the analysis, 606 of the patients were lost to follow-up or had aged out of the pediatric program, eight of whom had died due to their sickle cell disease.
Overall, the survival rate for the entire Dallas Newborn Cohort until age 25 years was 91.4% (95% CI, 88.4-93.7).
The 25-year survival rate for patients with sickle-hemoglobin C disease or beta-positive thalassemia was 98.6% (95% CI, 96.7-99.4). Patients with sickle cell anemia or beta-zero thalassemia had an 87.7% (95% CI, 83.3-91) survival rate, and in univariate analyses researchers found these genotypes were associated with early mortality.
Univariate analyses also indicated early mortality was associated with lower baseline hemoglobin and blood oxygen saturation levels.
In multivariate analyses, only lower baseline hemoglobin levels were associated with an increased risk for mortality (HR=0.76; 95% CI, 0.59-0.98).
Researchers noted the mortality rate increased in early adulthood.
“We’re quite pleased that a disease that has historically been associated with death in childhood is now demonstrating over 90% survival rates into adulthood, and we’re not seeing the degree of acceleration of early mortality one might expect in early adulthood,” McCavit said. “Nevertheless, the acceleration we do see is concerning, and we think merits a lot of focus on the 15- to 25-[year] age range.”
There may be several factors influencing that acceleration, McCavit said.
“We know that the transition of patients being followed in pediatric centers is complicated,” McCavit said. “I think that the drop-off may be in fact be biologically driven to an extent, but the care network that is available to older people with sickle cell disease is remarkably limited compared [with] the care network that is available to children. The extent to which under- or non-insurance is responsible for that is unknown, but I wouldn’t be surprised if it played a role.”
For more information:
Mathias MD. Abstract #559. Presented at: ASH Annual Meeting and Exposition; Dec. 6-9, 2014; San Francisco.Disclosure: The researchers report no relevant financial disclosures.