Biomarkers of splenic function in infants with sickle cell anemia: baseline data from the BABY HUG Trial

Abstract

We evaluated spleen function in 193 children with sickle cell anemia 8 to 18 months of age by (99m)Tc sulfur-colloid liver-spleen scan and correlated results with clinical and laboratory parameters, including 2 splenic biomarkers: pitted cell counts (PIT) and quantitative Howell-Jolly bodies (HJB) enumerated by flow cytometry. Loss of splenic function began before 12 months of age in 86% of infants in association with lower total or fetal hemoglobin and higher white blood cell or reticulocyte counts, reinforcing the need for early diagnosis and diligent preventive care. PIT and HJB correlated well with each other and liver-spleen scan results. Previously described biomarker threshold values did define patients with abnormal splenic function, but our data suggest that normal spleen function is better predicted by PIT of ≤1.2% or HJB ≤55/10(6) red blood cells and absent function by PIT ≥4.5% or HJB ≥665/10(6). HJB is methodologically advantageous compared with PIT, but both are valid biomarkers of splenic function. This trial was registered at www.clinicaltrials.gov as #NCT00006400.

Figure 1

HJB versus PIT counts. Individual patients are represented by a symbol on the scatter plot corresponding to their qualitative LS scan result. (●●●) represents patients with normal splenic uptake; (▩▩▩), patients with splenic function that is present but decreased; and (▵▵▵), patients with absent splenic function. The dashed horizontal line denotes a log₁₀ PIT count of 3.5%; and the vertical dashed line, log₁₀ HJB of 300/10⁶ RBCs.