How to define anemia in children with chronic kidney disease?

In a cross-sectional study, we compared the prevalence of anemia based on age- and gender-specific reference intervals for hemoglobin (Hgb) and hematocrit (Hct) with the Kidney Disease Outcomes Quality Initiative (KDOQI) anemia definition (Hgb < 110 g/L) in 351 children with chronic kidney disease (CKD) stages I-V. Cystatin C-based GFRs were 122 +/- 36 mL/min/1.73 m(2) in patients with stage I CKD (n=196), 76 +/- 8 mL/min/1.73 m(2) for stage II (n=104), 45 +/- 9 mL/min/1.73 m(2) for stage III (n=36), and 22 +/- 5 mL/min/1.73 m(2) in patients with stage IV+V CKD (n=15). Fifty-nine patients received iron therapy and 32 patients were treated with Darbepoetin. For Hgb, a total of 90 patients fit the age and gender derived criteria, compared to only 54 patients identified by the KDOQI guidelines (p=0.0010). Similarly, for Hct, a total of 78 patients fit the age and gender derived criteria, which was a significantly higher proportion than the 56 identified by the KDOQI guidelines (r=0.22, p=0.0435). There was a significant correlation between the GFR and both the Hgb Z-score (p=0.0068) and the Hct Z-score (p=0.0128). There was poor agreement between conventional and KDOQI definitions of anemia in children with CKD.