I am a medical director for a clinical laboratory so I will give you the answer why this would be the case in my human lab...
I suspect that the manufacturer of the equipment/test they are using to measure the insulin only measures up to 200. Basically that means that the instrument cannot accurately measure beyond 200. They cannot deviate from the manufacturer instructions. They would only be able to report higher if the manufacturer allowed dilutions of samples to effectively increase the reportable range. So if you mix 1 part sample and 1 part diluent (x2 dilution) you could report up to 400 (200 x2).
As you mentioned, it’s not always helpful to report >200 because there can be a huge clinical difference in much higher values. I am not sure what the highest insulin value would be that is still compatible with life, however. So it’s possible values much much higher are not relevant. Hope this makes sense.
May 2019, Minnesota
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