How to determine LoD, LoQ, Linearilty, Cutoff, Expected values for an IVD assay (infectious disease or physiological state monitoring eg. hormones).
Has anyone preformed these, can you explain the producer in simple terms?
I understand it involves statistical methods.
Hi Xin,
It would help if you could describe the assay you are working on. Please provide a copy of the calibration curve data for the assay because that has much of the information you are after. Ideally you would need to provide the calibration curve data obtained say every week throughout the shelf life of the IVD kit.
In very broad terms the LoD is 2 * SD of the signal observed for the zero standard.
The strict definition of the LoQ is the value of your lowest standard ..... because there is always a real difficulty in getting a matrix matched 'zero' sample.
Linearity is usually expressed qualitatively as "the assay was linear between 10 IU and 550 IU".
Cutoff is usually expressed as a value above which the IVD result becomes unreliable. But sometimes manufacturers use 'cutoff' as a diagnostic point eg. "Values below 400IU by our IVD are considered 'negative' for the disease". You will see below that Cutoff and Expected Values can sometimes be used interchangeably by IVD manufacturers
Expected values can refer to values expected you should obtain from quality control materials supplied with the IVD. Or they can refer to expected values (or cutoff values) in the clinical condition where the IVD is used ... eg "First trimetester
Thanks I'll see what I can make of them. Just so you know I head off on some overseas leave on 2nd March and will not be back until 14th March..... corona virus permitting !!
- Badges
- Science topic
- Similar topics
- Microbiology
- Assays