ORIGINAL ARTICLE How to define anemia in children with chronic kidney disease? Guido Filler & Kyle Mylrea & Janusz Feber & Hubert Wong Received: 25 April 2006 / Revised: 17 September 2006 / Accepted: 9 October 2006 / Published online: 10 January 2007 # IPNA 2007 Abstract 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. Keywords Guidelines . Chronic kidney disease . Children . Classification . Anemia Abbreviations CKD chronic kidney disease KDOQI kidney disease outcomes quality initiative Hgb hemoglobin Hct hematocrit GFR glomerular filtration rate Introduction The publication of the National Kidney Foundation’ s Dialysis Outcomes Quality Initiative (KDOQI) Clinical Practice Guidelines in 1997 represented the first compre- hensive effort to give evidence-based guidance for the management of patients with chronic kidney disease (CKD). The KDOQI guidelines have since been embraced around the world [1]. These guidelines have also been applied to children with CKD with regard to the manage- ment of their anemia and complications. The KDOQI guidelines are proposed despite a well- recognized age-dependency of hemoglobin and hematocrit [2]. KDOQI defines anemia in pre-menopausal females and pre-pubertal patients as Hgb<110 g/L, which fails to recognize this age-dependency [3]. Only in the most recent revision of the pediatric practice recommendations for anemia in chronic kidney disease, the guidelines have been revised to reflect the age dependency [4]. In older pediatric studies by the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) group, a hematocrit <0.33 was used similarly without considering the age dependency [5]. Treatment guidelines for Epoetin use are not age- dependent and largely based on outcome data using arbitrary cutoffs of Hgb 110 g/L and Hgb 120 g/L in adults [6]. The rationale for these recommendations stem from the Pediatr Nephrol (2007) 22:702–707 DOI 10.1007/s00467-006-0397-7 G. Filler : K. Mylrea : J. Feber : H. Wong Division of Pediatric Nephrology, Department of Pediatrics, Children’ s Hospital of Eastern Ontario, University of Ottawa, Ottawa, Canada G. Filler (*) Department of Pediatrics, Children’ s Hospital of Western Ontario, University of Western Ontario, 800 Commissioner ’ s Road East, London, ON N6A 5W9, Canada e-mail: guido.filler@lhsc.on.ca