The prevalence of bleeding disorders among healthy pediatric patients with abnormal preprocedural coagulation studies.

BACKGROUND: We evaluated the prevalence of hemostatic disorders among pediatric patients with abnormal screening coagulation tests. PROCEDURE: We analyzed 48 consecutive referrals for abnormal prothrombin times, partial thromboplastin times, or closure times obtained as preprocedural screens. Patients were evaluated by uniform diagnostic testing. RESULTS: Seventeen patients (35%) had an isolated nonspecific inhibitor (NSI). Six patients (12.5%) presented with mildly low factor activity with a concomitant NSI. These deficiencies were of unclear clinical significance. One patient (2%) had a lupus anticoagulant. Only 9 patients (19%) had a possible or true mild bleeding disorder: 5 patients (10%) had isolated low von Willebrand factor levels, 2 patients (4%) had possible type I von Willebrand disease, and 2 (4%) had platelet aggregation disorders. In all patients, personal and family bleeding history had a positive predictive value of 45% for hemostatic disorders. CONCLUSIONS: The most common diagnosis among the patients referred to us for abnormal preoperative coagulation tests was a NSI, which is not associated with an increased risk of operative bleeding complications. Less than 20% had a possible or true mild bleeding disorder. Although certain bleeding disorders can be occult in children and are associated with perioperative bleeding risks, our study demonstrates the inherent limitations in making a laboratory diagnosis of a bleeding disorder in pediatric patients preoperatively. Our findings contribute to existing doubt about the usefulness of prothrombin times, partial thromboplastin times, and closure times to identify occult bleeding disorders in this population.

Evidence for ineffective erythropoiesis in severe sickle cell disease.

Peripheral destruction of sickled erythrocytes is a cardinal feature of sickle cell disease (SCD). Less well established is the potential contribution of ineffective erythropoiesis to the pathophysiology of this hemoglobinopathy. Since patients with SCD frequently develop mixed hematopoietic chimerism after allogeneic nonmyeloablative stem cell transplantation, we used this opportunity to directly compare the differentiation and survival of SCD and donor-derived erythropoiesis in vivo. Donor and recipient erythropoiesis was compared in 4 patients with SCD and 4 without SCD who developed stable mixed hematopoietic chimerism following transplant. Molecular analysis of chimerism in peripheral blood and bone marrow demonstrated higher expression of donor-derived beta-globin RNA relative to the level of donor-derived genomic DNA in patients with SCD. Analysis of chimerism in immature (glycophorin A-positive [GYPA(+)], CD71(hi)) and mature (GYPA(+), CD71(neg)) erythroblasts confirmed the intramedullary loss of SS erythroblasts with progressive maturation. In patients with SCD, relative enrichment of donor erythroid precursors began to appear at the onset of hemoglobinization. Ineffective erythropoiesis of homozygous hemoglobin S (SS) progenitors thus provides a maturation advantage for homozygous hemoglobin A (AA) or heterozygous hemoglobin S/hemoglobin A (SA) donor erythroid precursor cells that results in greater donor contribution to overall erythropoiesis following stem-cell transplantation and improvement of clinical disease.