Trough value prediction using umbilical blood cystatin C value during tobramycin administration

Area of Science:

• Neonatal pharmacokinetics
• Pediatric pharmacology
• Clinical chemistry

Background:

• Aminoglycoside therapy, including tobramycin, is crucial in neonatal care but requires therapeutic drug monitoring.
• Estimating drug trough values non-invasively is essential to minimize risks associated with repeated blood draws in infants.

Purpose of the Study:

• To investigate the utility of umbilical cord blood serum creatinine (Cr) and cystatin C (CysC) for estimating neonatal tobramycin (TOB) trough values.
• To determine if cord blood biomarkers can predict TOB levels without increasing invasive testing risks.

Main Methods:

• A cohort of 16 infants treated with tobramycin from birth was studied.
• Cord blood Cr and CysC were measured, alongside tobramycin trough levels at 3 days of age.
• Correlations between cord blood biomarkers (adjusted for gestational week, birth weight, and body surface area) and TOB trough values were analyzed.

Main Results:

• Cord blood CysC adjusted for gestational week and body surface area (CysC/GW/BSA) demonstrated a strong correlation with tobramycin trough values (r=0.77).
• A cut-off value of 0.29 for CysC/GW/BSA effectively predicted TOB trough values ≥1 mg/mL (AUC: 0.927, sensitivity: 1.00, specificity: 0.75).

Conclusions:

• Umbilical cord blood CysC/GW/BSA is a reliable and non-invasive predictor of tobramycin trough levels in neonates.
• This method allows for early estimation of drug levels, facilitating dosage adjustments to prevent nephrotoxicity and reduce infant risks.