Which Analytes must have calibration linearity performed.  The one with less than 3 calibrators or more than 3 calibration points

You verify linearity by testing a low, mid, and high value along the AMR. What I've seen on the job is a low point needs to be within 50% of the low end of AMR and the high point needs to be within 10% of the high end of AMR. Those requirements are developed by the lab prior to verification, and are up to the pathologist.

Many times, calibrators satisfy this requirement if there are 3+ levels of calibrator. However, I've had some calibrators that do not sufficiently cover the AMR. I've either had to use additional samples to verify linearity in those cases, or you can change AMR to fit with what the calibrators can verify.