Correlation between vancomycin clearance and cystatin C-based glomerular filtration rate in paediatric patients

Aims: Because of limitations with the serum creatinine-based glomerular filtration rate (GFRcr), estimates of the serum cystatin C-based glomerular filtration rate (GFRcys) are getting attention to predict vancomycin clearance (CLvan). We evaluated the correlations between (i) CLvan and GFRcr, and (ii) CLvan and GFRcys in paediatric patients. Methods: We evaluated a retrospective cohort of patients between 1 and 19 years old admitted to a tertiary hospital between 2017 and 2019. CLvan was estimated using measured vancomycin trough concentrations. We conducted Spearman's correlation analyses between CLvan and 1/creatinine, GFRcr, 1/cystatin C and GFRcys. Subgroup analyses were conducted for the young child, child, adolescent subgroups, intensive care unit patients and low body weight (<10th percentile) patients. Results: We analysed 40 patients. GFRcys correlated with CLvan better than GFRcr did (ρ = 0.731, P < 0.001 vs ρ = 0.504, P = 0.001). In the subgroup analyses, the correlation between GFRcys and CLvan was stronger than that between GFRcr and CLvan (child subgroup ρ = 0.712, P = 0.002 vs ρ = 0.282, P = 0.289; intensive care unit patients ρ = 0.772, P < 0.001 vs ρ = 0.540, P = 0.004; low body weight patients ρ = 0.671, P < 0.001 vs ρ = 0.464, P = 0.022). Conclusions: Serum cystatin C-based GFR strongly correlates with vancomycin clearance, suggesting the possibility of better prediction models than creatinine-based GFR. Further prospective studies are required for the validation of the prediction model in a large paediatric population.