Evaluation of height-dependent and height-independent methods of estimating baseline serum creatinine in critically ill children.

BACKGROUND: Baseline serum creatinine (bSCr) is required for diagnosing acute kidney injury (AKI). In children, bSCr is commonly defined as the lowest measurement within 3 months of admission. Measured values are often missing and estimating bSCr using height-based glomerular filtration rate (GFR) equations is problematic when height is unavailable. METHODS: This is a retrospective cohort study including 538 children admitted to the intensive care unit (ICU) between 2003 and 2005 at two centers in Canada, with measured bSCr, height, and ICU-SCr values. We evaluated the bias, accuracy, and precision of back-calculating bSCr from height-dependent and height-independent GFR equations. Agreement of AKI defined using measured and estimated bSCr was calculated. Multivariate analyses were performed to assess the impact of bSCr estimation methods on the association between AKI and ICU mortality, length of stay, and duration of mechanical ventilation. RESULTS: Both methods underestimated bSCr by 1-3%, showed good accuracy (∼30% of patients with estimated bSCr within 10% of measured bSCr), but poor precision (wide 95% limits of agreement). The agreement between AKI defined by estimated versus measured bSCr was >80% (κ >0.5). The height-independent method performed best in children >13 years old; however, overall, both methods performed similarly across age subgroups. AKI was associated with longer stay, prolonged mechanical ventilation, and ICU mortality using measured and estimated bSCr. CONCLUSIONS: Height-dependent and height-independent bSCr estimation methods were comparable. This may have significant implications for performing pediatric AKI research using large databases, and in clinical care to define AKI when height is unknown.

Renal Function Follow-Up and Renal Recovery After Acute Kidney Injury in Critically Ill Children.

OBJECTIVES: To evaluate factors associated with renal recovery from acute kidney injury in critically ill children and the extent to which serum creatinine is measured before discharge. DESIGN: Retrospective cohort study. SETTING: Two PICUs at tertiary centers in Montreal, QC, Canada. PATIENTS: Children (< 18 yr old) admitted to the PICU between 2003 and 2005. Patients with end-stage renal disease, no healthcare number, died during admission, or admitted postcardiac surgery were excluded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Acute kidney injury was defined using internationally accepted criteria (Kidney Disease: Improving Global Outcomes). Two renal recovery outcomes commonly used in the literature were evaluated: hospital discharge serum creatinine less than 1.5 and less than 1.15 times baseline. Proportions of patients with 1) serum creatinine measurements between PICU and hospital discharge and 2) renal recovery were calculated. Univariate and multivariate analyses were performed to determine factors associated with serum creatinine monitoring and nonrecovery after acute kidney injury. Of 2,033 patients included, 829 (40.8%) had serum creatinine measurements between PICU and hospital discharge. The odds of having a discharge serum creatinine measurement increased with acute kidney injury severity (stages 1, 2, 3 adjusted odds ratio [95% CI]: 1.49 [1.03-2.15], 2.52 [1.40-4.54], 7.87 [3.16-19.60], respectively). Acute kidney injury recovery was 92.5% when defined as serum creatinine less than 1.5 times baseline versus 75.9% when defined as less than 1.15 times baseline (p < 0.001). Stage 3 acute kidney injury was associated with having a discharge serum creatinine greater than or equal to 1.5 times baseline (adjusted odds ratio = 3.51 [1.33-9.19]). CONCLUSIONS: Less than half the PICU population had serum creatinine measured before hospital discharge. More severe acute kidney injury was associated with higher likelihood of serum creatinine monitoring and lower probability of acute kidney injury recovery. Future research should address knowledge translation on post-PICU acute kidney injury follow-up before hospital discharge.

Estimation of glomerular filtration rate with and without height: effect of age and renal function level.

BACKGROUND: The current glomerular filtration rate (GFR) equation (CKiD) may be less accurate in adolescents and children with higher GFR. METHODS: This was a retrospective study (n = 161, 247 (99)mTc DTPA-GFRs). Six equations were evaluated for bias, accuracy, and low GFR diagnosis: (1) CKiD; (2) historic center; (3) Hoste(age); (4) Hoste(height); (5) modified Pottel; (6) Gao. Children with ≥ vs. <90 ml/min/1.73 m(2)) and < vs. ≥16 years were compared. Two adult equations were evaluated in children ≥16 years. RESULTS: Most equations underestimated GFR by 1-14 % in the higher GFR group, least so for Hoste(age). In the low GFR group, Hoste(age) and historic center overestimated GFR significantly more than CKiD (p < 0.05). Accuracy (within 30 % GFR) was similar across equations and GFR subgroups (66-86 %). In the ≥16 years group, CKiD underestimated GFR by ∼10 %, vs. ∼3 % for Hoste(height). Accuracy was 5-10 % lower in the older group and most equations were more sensitive than specific for detecting low GFR; this discrepancy was less for the Hoste equations. Adult equations were highly inaccurate. CONCLUSIONS: GFR estimation in older children and with higher GFR is suboptimal. The Hoste(height) may be an alternative GFR estimation method; Hoste(age) may allow for height-independent GFR estimation in patients with normal GFR.