Renal Functions Tests (RFT) PDF

Renal Functions Tests (RFT) Fatima Yousuf Mohamed MSc Clinical Chemistry Objectives To discuss the clinical significance of RFT. To identify the conditions in which we perform RFT. To understand tests of renal function.  What...

Renal Functions Tests (RFT) Fatima Yousuf Mohamed MSc Clinical Chemistry Objectives To discuss the clinical significance of RFT. To identify the conditions in which we perform RFT. To understand tests of renal function.  What are the renal functions? Clinical significance of RFT Assess the functional capacity of the kidney. Diagnosis of renal diseases. Prognosis and severity of renal diseases. Monitor response to treatment. Medication management. Early detection of possible renal impairment. Renal functions should be assessed in the following conditions: Family history of chronic kidney disease Diabetes Mellitus (DM) Hypertension Elderly Autoimmune disease Systemic infections Urinary tract infection Drug toxicity Renal calculi Renal function tests Are group of tests performed together to evaluate renal functions. Include the following: Urine analysis Glomerular function tests Tubular function tests Glomerular function tests Blood urea and BUN Serum creatinine BUN: creatinine ratio Serum uric acid Clearance Measurements Clearance Measurements Clearance is defined as that volume of plasma from which certain substance can be completely eliminated into the urine per unit of time (ml/min). Substance used should be: Synthesized at a constant rate Completely filtered by the glomeruli Neither reabsorbed nor secreted by the renal tubules. Easily measured, available and inexpensive Markers (substances) used to assess clearance Endogenous markers such as: creatinine, Cystatin C. Exogenous marker such as: inulin. Clearance Measurements Cont… Measurement of clearance is used to estimate the Glomerular Filtration Rate (GFR). GFR is defined as the volume of plasma filtered by glomerular capillaries per unit of time. Creatinine Clearance Calculation of creatinine clearance has become the standard laboratory method to determine GFR. CCr = UCr (mg/dL) × VUr (mL) ×1.73 PCr(mg/dL) × 1440 (min) A Where:  CCr is creatinine clearance  UCr is urine creatinine  VUr is urine volume excreted in 24 hours  PCr is serum creatinine concentration  1.73 is the generally accepted average body surface A is the actual body surface area of the individual Reference Ranges Female: 88 – 128 ml/min Male: 97 – 137 ml/min Decreased result in : Physiological decrease with age, with a decrease of about 6.5 mL/min for each decade of life. Pathological decrease as in renal failure. Serum creatinine inversely proportional to Creatinine Clearance Estimated Glomerular Filtration Rate Cockcroft-Gault formula GFR (mL/min) =(140 - Age)×Weight(kg) 72 × SCr(mg/dL) × (0.85 if female)*  Urine microalbumin &albumin: creatinine ratio The term microalbuminuria describes small amounts of albumin in urine. Important in the management of patients with diabetes mellitus who are at risk of developing nephropathy overtimes. Quantitative albumin-specific immunoassays, usually using nephelometry or immunoturbidimetry, are widely used.  Normally the urinary excretion of albumin is