Secondary hyperparathyroidism and anemia in children treated by hemodialysis

Abstract

Background: Many patients treated using hemodialysis remain anemic despite exogenous erythropoietin therapy, suggesting that the anemia experienced by these patients is multifactorial in cause. Iron deficiency, infection, inflammation, and malnutrition have been implicated in this process. Additionally, secondary hyperparathyroidism has been associated with anemia in adults, but few data exist about this topic in children.

Study design: Cross-sectional retrospective.

Setting & participants: Children treated in hemodialysis centers (N = 588) within the Centers for Medicare & Medicaid Services' 2002 Clinical Performance Measures Project.

Predictor: Intact parathyroid hormone (iPTH) levels assessed in October, November, and December 2001 and categorized as quintiles.

Outcomes & measurements: Achievement of serum hemoglobin level > or = 11 g/dL was assessed using Poisson regression adjusting for sex, age, race, dialysis vintage, vascular access type, single-pool Kt/V, serum albumin level, normalized protein catabolic rate, calcium-phosphorus product, and erythropoietin alfa dose.

Results: Using the second quintile (iPTH, 103-224 pg/mL) as the reference quintile, there was no association between iPTH quintile and achievement of the hemoglobin goal: quintile 1 prevalence ratio, 1.0 (95% CI, 0.9-1.2); quintile 3, 0.95 (95% CI, 0.8-1.1); quintile 4, 0.99 (95% CI, 0.8-1.2); and quintile 5, 0.97 (95% CI, 0.8-1.1). Only serum albumin level >/= 3.5 g/dL (bromocresol green assay method) or > or = 3.2 g/dL (bromocresol purple assay method) was significantly associated with meeting the hemoglobin goal: 1.4 (95% CI, 1.2-1.6).

Limitations: The simultaneous collection of iPTH and hemoglobin limits causal inference. Iron stores and iron therapy are potential confounders not accounted for in this study.

Conclusions: In the largest study of this topic in children, no association was found between iPTH level and achievement of a hemoglobin level > or = 11 g/dL. Serum albumin level was associated strongly with achievement of the hemoglobin goal.

Figure 1

Median and interquartile range of hemoglobin levels stratified by iPTH quintiles. Raw data for PTH quintiles: 1, ≤108 pg/ml; 2, >108–≤246 pg/ml; 3, >246 – ≤431 pg/ml; 4, <431 – ≤808 pg/ml; 5, >808 pg/ml. Conversion factor for serum hemoglobin in g/dl to g/L, ×10; no conversion necessary for intact PTH in pg/ml and ng/ml.