49 - Cystatin C as a biomarker for early AKI in critical ill neonates using scavenged specimens

Poster Number: 49
Publication Number: 49.2037

Background: Neonatal acute kidney injury (AKI) is a potentially preventable mortality, morbidity, chronic lung disease, and chronic kidney disease risk factor with incidence of 30% in the first 7 days of life (DOL). The current neonatal AKI definition uses serum creatinine (SCr) and urine output, which have several limitations. While AKI is potentially reversible, SCr lags by 48-72h. Serum Cystatin C (CysC) is freely filtered without tubular section and completely metabolized by the proximal tubule, though reliability to predict AKI is not established in premature infants. Timely identification of AKI using CysC could allow successful intervention to decrease morbidity in high-risk infants.

Objective: Our primary aim was to compare CysC in critically ill infants with and without early AKI (within 7 DOL). We hypothesize CysC will be significantly higher in infants with AKI compared to those without AKI (defined by SCr criteria).

Design/Methods: This is an observational pragmatic study approved by BCM IRB. We obtained biospecimens collected for clinical purposes. We screened all hospitalized neonates for inclusion by high-risk criteria for AKI (hypoxic ischemic encephalopathy, low birth weight, prematurity, suspected sepsis, nephrotoxin exposure, mechanically ventilated, vasoactive medication, and congenital heart defects (CHD)) and exclusion criteria (> 14 DOL, not expected to survive >24 HOL, mortality < 48 HOL, known congenital anomalies of the kidney and urinary tract, or renal replacement therapy before available scavenged labs). We recorded confounders such as maternal/infant demographics, pertinent clinical data and interventions, comorbidities, and nephrotoxin exposure. We performed univariate analysis for the relationship between AKI and CysC (Quantikine ELISA).

Results: 86 infants were included in this interim analysis. 12 (14%) did not have two SCr to determine AKI status. Of the remaining 74, 11 (15%) had AKI (55% Stage 3, 45% Stage 1) and 63 (85%) did not have AKI by SCr. Those with AKI were significantly more likely to have CHD, pulmonary hypertension, and receive vasoactives, TPN, and ECMO (Table 1). Those without AKI were more likely to be an infant of a diabetic mother and to survive to discharge (Table 1). CysC by ELISA did not significantly differ by AKI status (AKI: 2.8396 [2.3136, 4.5376], non-AKI: 2.971.9 [2.5740, 3.6743] mg/L, p=0.89).

Conclusion(s): An opportunistic approach to study biomarkers in critically ill neonates with residual biospecimens can be successful to study CysC. In this interim analysis, CysC was not significantly different in patients with early AKI by KDIGO SCr criteria.