Serum Cystatin C May Help Predict AKI Risk in Children

In children undergoing heart surgery, increases in serum cystatin C during the early postoperative period are associated with an increased rate of acute kidney injury (AKI), suggests a study in Kidney International.

The prospective study included 288 children undergoing cardiac surgery at three children’s hospitals. One-half were aged 2 years or younger. Preoperative and postoperative cystatin C were evaluated as predictors of AKI. The predictive value of cystatin C was compared with that of serum creatinine-based estimates of glomerular filtration rate.

Stage 1 AKI or worse developed in 42 percent of the children and stage 2 AKI or worse in 11 percent. Children with higher preoperative creatinine-based estimated glomerular filtration rates were at higher risk of AKI: adjusted odds ratio (OR) 1.5 for stage 1 and 1.9 for stage 2 AKI.

Preoperative cystatin C was unrelated to AKI risk. However, children in the highest quintile of postoperative cystatin C were at significantly increased risk: OR 6.0 for stage 1 and 17.2 for stage 2 AKI. Being in the highest tertile of percent change in cystatin C was independently associated with AKI risk; being in the highest tertile of serum creatinine predicted stage 1 but not stage 2 AKI. Postoperative change in both cystatin C and creatinine predicted longer ICU stay, while postoperative change in cystatin C also predicted duration of mechanical ventilation.

Early diagnosis of AKI is particularly challenging in children. The new study suggests that early postoperative increases in serum cystatin C may predict the development of AKI in children undergoing cardiac surgery. Postoperative cystatin C may be useful for risk stratification in AKI treatment trials. More study of the association between preoperative renal function and AKI risk is needed [Zappitelli M, et al: Early postoperative serum cystatin C predicts severe acute kidney injury following pediatric cardiac surgery. Kidney Int 2011; 80: 655–662].

October 2011 (Vol. 3, Number 10 & 11)