This guideline is really aimed at secondary care as it will be the worst affected patients that suffer with hyperphosphataemia. However, we do have some stable CKD4 patients just under primary care, so it is worth remembering that this can be an issue.
Basically, patients with CKD 4 or 5, should have their phosphate levels checked regularly. They don't specify how often. The NICE CKD guidance just says to judge how often based upon initial readings and to seek specialist advice if uncertain. Limits vary from area to area, but you are aiming for a level of 0.9 to 1.5 mol/l in dialysed patients.