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Forced expiratory volume in 1 second predicts sickle cell anemia death
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A decreased forced expiratory volume in 1 second corresponded with earlier death in adult patients with sickle cell anemia, according to the results of a prospective cohort study.
However, obstructive and restrictive pulmonary function patterns did not predict earlier death in adult patients, according to the researchers.
“In the largest prospective cohort study completed investigating the natural history of sickle cell disease in children and adults, the Cooperative Study of Sickle Cell Disease (Platt OS, et al. N Engl J Med. 1994;330(23):1639-1644.) noted an increased risk of earlier death in patients with sickle cell anemia was associated with acute chest syndrome, renal failure, seizures, and elevated baseline white cell count and a low level of fetal hemoglobin,” Michael Rutledge DeBaun, MD, MPH, professor of pediatrics and medicine at Vanderbilt University School of Medicine and director of Vanderbilt-Meharry Center for Excellence in Sickle Cell Disease, and colleagues wrote. “In sickle cell anemia, no single attribute of pulmonary function test results has been associated with earlier death.”
DeBaun and colleagues sought to test a hypothesis that abnormal pulmonary function resulted in earlier death from sickle cell anemia. They constructed a prospective cohort using data from the Cooperative Study of Sickle Cell Disease.
The analysis included data from 430 black participants with sickle cell anemia who completed at least one pulmonary function test when aged older than 21 years. The researchers measured forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and total lung capacity (TLC) and categorized results based on age, sex, height and race.
The Cooperative Study of Sickle Cell Disease recorded patient deaths in the clinical record; however, they did not note cause of death for all deaths, and the availability of autopsy information varied. The researchers computed patient follow-up from the date of lung function testing until one of the following: bone marrow transplantation, last Cooperative Study of Sickle Cell Disease visit or death.
The mean age at time of first pulmonary function test was 32.6 years (± 9.5 years). Median follow-up was 5.5 years.
Fifteen percent of the cohort (n = 63) died during follow-up. Forty-seven percent of patients who died had normal pulmonary function patterns, whereas 29% had restrictive patterns, 8% had obstructive patterns, 2% had mixed patterns and 14% had non-specific pulmonary function patterns.
Results of a multivariable analysis indicated risk for earlier death appeared associated with lower FEV1 (HR = 1.02; 95% CI, 1-1.04), older age (HR = 1.07; 95% CI, 1.04-1.1), male sex (HR = 2.09; 95% CI, 1.2-3.65), higher lactate dehydrogenase levels (HR per mg/dl = 1.002; 95% CI, 1-1.003) and higher acute chest syndrome incidence rate (HR per event/year = 10.4; 95% CI, 3.11-34.8).
However, the presence of obstructive (HR = 1.18; 95% CI, 0.44-3.20) and restrictive (HR = 1.31; 95% CI, 0.64-2.32) pulmonary function patterns did not increase risk for earlier death.
The researchers acknowledged that the potential for misclassification of pulmonary function abnormalities and the exclusion of lung diffusion capacity tests in the analysis may be limitations to these findings. Further, the researchers noted that the initial data were collected at a time when disease modifying therapy, such as hydroxyurea, was not frequently used.
“As has been the case in individuals with cystic fibrosis, potential therapeutic intervention, such as macrolide therapy, can be evaluated to determine if FEV1 predicted values can be increased,” DeBaun and colleagues wrote. “Such strategies may enable intervention for those deemed at risk for early death in a population where cardiopulmonary disease is the main cause of death and only one disease modifying therapy has been approved by the FDA.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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