Biomarkers in sickle cell disease.

More than 100 different blood and urine biomarkers have been described in sickle cell disease (SCD), with the number increasing rapidly as analytical techniques develop. Nearly all of these biomarkers are abnormal in the steady state, and become more so during complications. The range of abnormalities demonstrates the multisystem nature of SCD and the complex pathophysiology. Some biomarkers indicate damage to specific organs, such as urine albumin:creatinine ratio in nephropathy, whereas others indicate more systemic processes. Biomarkers have been useful in identifying various interrelated pathological mechanisms, including haemolysis, inflammation, hypercoagulability, oxidative stress, reperfusion injury, vasculopathy and endothelial dysfunction. However, most biomarkers correlate closely with other more routine measurements, and also with each other. It is not clear that any provide specific prognostic or clinical information beyond that given by the simple measurement of haemoglobin concentration. The identification of prognostically validated biomarkers in prospective clinical trials would be useful.