Long-Term Effects of Hydroxyurea in Children With Sickle Cell Anemia (The BABY HUG Follow-up Study)

• Comparison of the proportion of infants with decreased or absent spleen function [ Time Frame: Measured at Years 2 and 4 (or at the end of the study, whichever comes first) ] [ Designated as safety issue: Yes ]
• Comparison of kidney damage, as measured by glomerular filtration rate (GFR) [ Time Frame: Measured at Years 2 and 4 (or at the end of the study, whichever comes first) ] [ Designated as safety issue: Yes ]

Sickle cell anemia (SCA) is an inherited blood disorder that can cause organ damage. The BABY HUG study is evaluating the use of the medication hydroxyurea at preventing organ damage in children with SCA. The purpose of this follow-up study is to evaluate the long-term effects of hydroxyurea in children who have participated in the BABY HUG study.

SCA is an inherited blood disorder in which the body makes sickle-shaped red blood cells that contain abnormal hemoglobin. The sickled cells block blood flow in the vessels that lead to limbs and organs. This can cause pain, serious infections, and organ damage. The BABY HUG study (NCT00006400) is examining whether the medication hydroxyurea can prevent organ damage, especially in the spleen and kidneys, in children with SCA. This study is a follow-up study to the BABY HUG study and will enroll children who have participated in the BABY HUG study. The purpose of this study is to examine the long-term effects of using hydroxyurea as a treatment for SCA, including both the risks and benefits. Study researchers will also investigate the optimal age to begin treatment with hydroxyurea in children with SCA.

This study will enroll children between 2 and 7 years old who participated in the BABY HUG study. Hydroxyurea will not be provided to participants as part of this study, but participants may receive the medication from their own doctors. Parents of participants can choose for their child to participate in this study in one of two ways—by enrolling in either a passive follow-up group or an active follow-up group. For participants in the passive follow-up group, study researchers will review participants' medical records every 6 months, in addition to reviewing brain ultrasound tests and computed tomography (CT) or magnetic resonance imaging (MRI) scans, if completed. Participants will have a blood and urine collection at baseline and Year 4 (or at the end of the study, whichever comes first). Participants in the active follow-up group will take part in the same study procedures as participants in the passive follow-up group. In addition, at Year 2, participants in this group will undergo an additional blood and urine collection, a scanning procedure to obtain images of the liver and spleen, a kidney test, neuropsychological testing, and an ultrasound imaging test to evaluate liver and spleen size.

Children from the initial BABY HUG study who agree to participate in this follow-up study.

• 1
  Participants in the active follow-up group.
• 2
  Participants in the passive follow-up group.

Inclusion Criteria:

• All children who completed at least 18 months of follow-up visits in the initial BABY HUG study
• Children from the initial BABY HUG study who are on a chronic transfusion program or who are recipients of a bone marrow transplant

Exclusion Criteria:

• Any child who was not enrolled in the initial BABY HUG study for at least 18 months