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.
Jaffe method
Kinetic jaffe method
Technicon method
Enzyme assay