The investigators will attempt to develop a more accurate equation to estimate eGFR in pediatric and adult sickle cell patients

200 pediatric and 200 adult SCA participants will undergo mGFR using iohexol at baseline and at one year. On the same day, participants will undergo clinical and laboratory variables important for developing an eGFR equation. From baseline data, the investigators will perform a training and validation cohort of biologically relevant predictor variables to develop a novel equation. Then the investigators will compare the novel SCA eGFR equation to the established eGFR equation. From one year data, the investigators will determine the longitudinal concordance between pediatric and adult novel and standard eGFR equations with mGFR and variables that may alter longitudinal inferences.

In a subset of 30 adult participants, the investigators will also evaluate the correlation between mGFR using iohexol and a novel measure of mGFR that is more time efficient

Inclusion Criteria:

• SCA patients (HbSS and SB0 thalassemia)
• Age: 5.0-50.0 at enrollment

Exclusion Criteria:

• Recent SCA complication associated with hospitalization (within 30 days) or ED visit (within 14 days)
• Current AKI defined as >0.3mg/g increase in SCr from prior visit
• Known history of anaphylaxis with contrast agent or known pregnancy

Patients with sickle cell anemia

Data collected in this study will be made available to other researchers, after the goals have been met and primary aims have been published. Disclosure of sensitive health and behavior data present a potential risk to human subjects, and we will take all steps to ensure that this does not happen when data are shared. In addition, we will strongly recommend that all recipient groups ensure that every member of the staff sign a Confidentiality Agreement. We will develop a data and resource sharing agreement with the legal advice from the Compliance Office of the UAB. Before data is shared with researchers, we will require that researchers enter into a data- and resource-sharing agreement. This agreement will ensure that: 1) data are used only for research purposes; 2) data do not identify any individual participant; 3) data are secure, using appropriate computer technology; and 4) there is a commitment to destroy or return data after analyses are completed.