The<unk>  is a colorimetric method used in clinical chemistry to determine creatinine levels in blood and urine. In 1886, Max<unk>  (1841–1911) wrote about its basic principles in the paper Über den Niederschlag, welchen Pikrinsäure in normalem Harn erzeugt und über eine neue<unk>  des Kreatinins in which he described the properties of creatinine and picric acid in an alkaline solution. The color change that occurred was directly proportional to the concentration of creatinine, however he also noted that several other organic compounds induced similar<unk> s. In the early 20th century, Otto Folin adapted<unk> 's research into a clinical procedure. The<unk> , despite its nonspecificity for creatinine, is still widely employed as the method of choice for creatinine testing due to its speed, adaptability in automated analysis, and cost-effectiveness, and is the oldest methodology continued to be used in the medical laboratory. It is this nonspecificity that has motivated the development of new reference methods for creatinine analysis into the 21st century.
Jaffe reaction
Agar dilution
Jones' stain
Wayson stain
Mixed-field agglutination
Feulgen stain
Welner table
Simpson test