I have a data set of 450 subject with each having 3 repeated measurements using a new device. I want to compare these measurements with the gold standard measurement (which I have a single measurement) and show the good correlation with the gold standard. measurements are continuous variables. I'm a little bit confused which statistical test I should use. Initially I used to calculate means of 3 repeated measurements and compare it using Spearman Correlation. Is it okay to use Inter Class Correlation so simple R2, or the best way is to use some sort of repeated measure test?

Thanks,