Clinical decision interval

Hi all,

I have a question regarding clinical decision intervals (grey zone).
We have developed a new screening test and we want to provide the physician with an interval on which he can base his decision.
A total of 74 men were recruited. All samples were analysed both with the new screening test and the gold standard (the latter provides a cut-off. However, this cut-off tends to change over time).
Unfortunately, we don't have any information on the clinical aspects of the patients.
I grouped the patients based on the cut-off of the gold standard and performed a ROC analysis.
As the screening test is a subjective method, the total variance is relatively high. For this reason, we want to provide an interval.
My question is, what is the correct method to calculate this interval?

Thank you in advance!
Maybe I'm telling complete nonsense here, but would it be an idea to calculate the variance of intermediate precision and to use this value in a z-test?