Serum creatinine REF: Harrison's Internal Medicine 17' edition chapter 274 The most impoant initial diagnostic step in the evaluation of a patient presenting with elevated serum creatinine is to distinguish newly diagnosed CKD from acute or subacute renal failure because the latter two conditions may respond to therapy specific to the disease. Previous measurements of plasma creatinine concentration are paicularly helpful in this regard. Normal values from recent months or even years suggest that the current extent of renal dysfunction could be more acute, and hence reversible, than might otherwise be appreciated. In contrast, elevated plasma creatinine concentration in the past suggests that the renal disease represents the progression of a chronic process. Even if there is evidence of chronicity, there is the possibility of a superimposed acute process, such as ECFV depletion, supervening on the chronic condition. If the history suggests multiple systemic manifestations of recent onset (e.g., fever, polyahritis, and rash) it should be assumed that renal insufficiency is pa of the acute process. From the following staging of CKD based on GFR it is clear that GFT can be even normal in initial staged of CKD Clinical action plan Stage Description GFR, mL/min per 1.73 m2 Action' 1 Kidney damage with normal or +GFR > or = 90 Diagnosis and treatment, treatment of comorbid conditions, slowing progression, CVD risk reduction 2 Kidney damage with mild +GFR 60-89 Estimating progression 3 Moderate +GFR 30-59 Evaluating and treating complications 4 Severe +GFR 15-29 Preparation for kidney replacement therapy 5 Kidney failure <15 (or dialysis) Kidney replacement (if uremia present)