Which statement about the EMIT assay is true?

The statement regarding the EMIT assay that is correct indicates that the formation of NADH is monitored at 340 nm. In EMIT (Enzyme Multiplied Immunoassay Technique), the assay relies on the enzyme activity that is coupled with the binding of a drug to an antibody. This reaction typically involves the conversion of a substrate to a product, and NADH (Nicotinamide adenine dinucleotide) is a common coenzyme that is produced in such reactions. The absorption of NADH occurs at a wavelength of 340 nm, which allows for the quantification of enzyme activity and, subsequently, the determination of drug levels.

Utilizing the monitoring of NADH production is key to this assay as it provides a reliable means of measuring enzyme-catalyzed reactions linked to the presence of the target drug. The concentration of the drug in the sample will affect this reaction's dynamics, which is critical in determining the drug levels accurately.

The other options do not accurately describe the EMIT assay. For instance, although enzyme activity is related to drug concentration, it is not typically stated that it is inversely proportional to the drug level. Instead, enzyme activity is directly proportional to the amount of free drug available that does not bind to