Direct assay of acetoacetate in serum, plasma, urine and other biological samples. Sensitive and accurate. Linear detection range of 0.012 to 1 mM (1.2 – 100 nmole/well) for acetoacetate in 96-well plate assay. Convenient. No sample pretreatment needed. The procedure involves adding a single working reagent and reading the optical density at room temperature in kinetic mode. High-throughput. Can be automated as a high-throughput 96-well plate assay for thousands of samples per day. Method: OD550nm. Samples: Serum, plasma, urine, and other biological samples. Procedures: 30 min. Size: 100 tests in 96-well plate.