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Degree of Anemia, Indirect Markers of Hemolysis, and Vascular Complications of Sickle Cell Disease in Africa.

Marie Dubert, Jacques Elion, Aissata Tolo, Dapa Aly Diallo, Saliou Diop, Ibrahima Diagne, Ibrahima Sanogo, Suzanne Belinga, Odette Guifo, Guillaume Wamba, Françoise Ngo Sack, Kouakou Boidy, Ismael Kamara, Youssouf Traore, Cheick Oumar Diakite, Valérie Gbonon, Blaise Felix Faye, Moussa Seck, Indou Deme Ly, David Chelo, Roland N'Guetta, Ibrahima Bara Diop, Bamba Gaye, Xavier Jouven and Brigitte Ranque

Key points

  • Severe baseline anemia is associated with leg ulcer, microalbuminuria and echographic pulmonary hypertension in African sickle cell disease patients.

  • These vascular complications of sickle cell disease are not independently associated with indirect markers of increased hemolysis.

Abstract

The hyperhemolysis paradigm that describes overlapping "hyperhemolytic-endothelial dysfunction" and "high hemoglobin-hyperviscous" subphenotypes of sickle cell disease (SCD) patients is based on North American studies. We performed a transversal study nested in the CADRE cohort to analyze the association between steady-state hemolysis and vascular complications of SCD among sub-Saharan African patients. In Mali, Cameroon, and Ivory Coast, 2,407 SCD patients (1,751 SS-Sβ0, 495 SC and 161 Sβ+), aged three years old and over, were included at steady-state. Relative hemolytic intensity was estimated from a composite index derived from principal component analysis, which included bilirubin levels or clinical icterus, and lactate dehydrogenase levels. We assessed vascular complications (elevated tricuspid regurgitant jet velocity (TRV), microalbuminuria, leg ulcers, priapism, stroke, and osteonecrosis) by clinical examination, laboratory tests, and echocardiography. After adjustment for age, sex, country, and SCD phenotype, a low hemoglobin level was significantly associated with TRV and microalbuminuria in the whole population and with leg ulcers in SS-Sβ0 adults. A high hemolysis index was associated with microalbuminuria in the whole population and with elevated TRV, microalbuminuria, and leg ulcers in SS-Sβ0 adults, but these associations were no longer significant after adjustment for hemoglobin level. In conclusion, severe anemia at steady-state in SCD patients living in West and Central Africa is associated with elevated TRV, microalbuminuria, and leg ulcers, but these vascular complications are not independently associated with indirect markers of increased hemolysis. Other mechanisms leading to anemia, including malnutrition and infectious diseases, may also play a role in the development of SCD vasculopathy.

  • Submitted December 22, 2016.
  • Accepted September 2, 2017.