title: Biochemical surrogate markers of hemolysis do not correlate with directly measured erythrocyte survival in sickle cell anemia.
abstract: Hemolysis is a key feature of sickle cell anemia (HbSS). Direct quantitation of hemolysis could be used as an objective outcome in clinical trials of new therapeutics for HbSS and would also enable better human studies of the pathogenesis of complications of HbSS that are ostensibly hemolysis-related, such as pulmonary hypertension. However, contemporary human studies in HbSS have used only surrogate markers of hemolysis rather than direct measurements of RBC survival. We directly quantified hemolysis in HbSS by measuring survival of an age cohort of RBCs labeled with a stable isotope, administered orally as15N-glycine, a metabolic precursor of heme. The atomic excess of15N in heme extracted from blood was monitored by mass spectrometry over time. We performed 13 labeling experiments in 11 individuals with HbSS. Mean RBC survival was 31.9 days (range 14.1-53.6). Both HbF level, a known determinant of hemolysis, and absolute reticulocyte count (ARC), an index of the marrow's response to hemolysis, correlated with directly measured RBC survival (r = 0.61, P < 0.002; r = -0.84, P < 0.001). However, commonly used biochemical surrogates of hemolysis (LDH, AST, bilirubin, and plasma free hemoglobin) did not correlate with directly measured RBC survival. These biochemical surrogates should be interpreted cautiously, at best, in clinical trials and human physiologic studies in HbSS. ARC was the best correlate of total hemolysis, but only 70% of the variation in RBC survival was reflected in this marker. If greater accuracy is required in human studies,15N-glycine RBC labeling can directly and accurately quantify hemolysis. Am. J. Hematol. 91:1195-1201, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.|Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Quinn
authors.affiliation: Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Eric P
authors.initials: EP
authors.lastname: Smith
authors.affiliation: Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Shahriar
authors.initials: S
authors.lastname: Arbabi
authors.affiliation: Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Paramjit K
authors.initials: PK
authors.lastname: Khera
authors.affiliation: Department of Emergency Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lindsell
authors.affiliation: Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.|Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Omar
authors.initials: O
authors.lastname: Niss
authors.affiliation: Aflac Cancer and Blood Disorders Center, Emory University School of Medicine, Atlanta, GA.
authors.forename: Clinton H
authors.initials: CH
authors.lastname: Joiner
authors.affiliation: Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Franco
authors.affiliation: Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH.|Cincinnati Veterans Affairs Medical Center, Cincinnati, OH.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D000755:Anemia, Sickle Cell / Q000473:pathology*; D015415:Biomarkers / Q000097:blood*; D002470:Cell Survival; D004912:Erythrocytes / Q000473:pathology*; D005260:Female; D005319:Fetal Hemoglobin; D005998:Glycine / Q000008:administration & dosage; D006461:Hemolysis; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes / Q000008:administration & dosage*; D017701:Reticulocyte Count; D055815:Young Adult
chemical_list: D015415:Biomarkers; D009587:Nitrogen Isotopes; D005319:Fetal Hemoglobin; D005998:Glycine