Renal Function Tests
Blood tests assessing kidney function, primarily serum creatinine and estimated glomerular filtration rate (eGFR). Renal function monitoring is important for peptide drugs cleared by the kidneys and for nephrotoxic antimicrobial peptides (colistin, polymyxin B, vancomycin) that require dose adjustment.
Technical Context
Key parameters: serum creatinine (muscle-derived waste product filtered by kidneys — elevated when GFR falls), eGFR (estimated from creatinine using CKD-EPI equation incorporating age, sex, and race — normal >90 mL/min/1.73m²; CKD staged by eGFR: G1 ≥90, G2 60-89, G3a 45-59, G3b 30-44, G4 15-29, G5 <15), BUN/urea (less specific than creatinine), cystatin C (alternative filtration marker, less affected by muscle mass), and urine albumin:creatinine ratio (UACR — detecting albuminuria, an early marker of kidney damage). For peptide drugs: dose adjustment required for renally-cleared peptides in CKD (colistin, polymyxin B, vancomycin — requiring TDM); difelikefalin is specifically dosed for haemodialysis patients; GLP-1 RAs generally do not require dose adjustment in mild-moderate CKD but caution with dehydration risk from GI side effects; semaglutide FLOW trial investigated kidney outcomes in T2D patients with CKD.