Creatinine determination according to Jaffe--what does it stand for?

In 1886, Max Jaffe discovered a reaction of creatinine with picric acid in an alkaline environment. Although the manuscript describes the nature of a precipitate and does not deal with an analytical assay, Jaffe's landmark paper elucidated the basic principles of the creatinine determination method (originally developed by Otto Folin), which became immensely popular and has easily withstood the test of time. Despite the advent of the enzymatic creatinine analysis, the analytical method is still popular due to its simplicity and low cost. As there is no standard recipe for the 'Jaffe' method, much methodological variation has occurred over time. This lack of methodological standardization implies that even in the 21st century, improving the interchangeability of Jaffe results is still an issue.