Which of the following estimates blood creatinine level most accurately -

Among the given options, the enzyme assay is the most accurate. Methods to measure serum creatine to assess GFR are:- i) Gas chromatography-isotope dilution mass spectroscopy (GC-IDMS):- It is the most accurate and method of choice. ii) High-performance liquid chromatography (HPLC). (iii) Enzymatic creatinine method (enzyme assay). (iv)Alkaline picrate methods:- Jaffe method Accuracy in decreasing order is GC-IDMS > HPLC > Enzyme assay > Alkaline picrate (Jaffe) method.