Routine monitoring of a patient with monoclonal gammopathy of undetermined significance (MGUS) should include serum protein electrophoresis and serum-free light-chain assay to detect and quantify the paraprotein and assess for changes indicating progression towards myeloma or related disorders.
If serum protein electrophoresis is abnormal, serum immunofixation should be performed to confirm the presence and type of paraprotein.
Urine testing for Bence–Jones protein (urine electrophoresis) may be considered if serum free light chain testing is not available, but it should not be used alone to exclude myeloma.
Regular monitoring should also include assessment of renal function and calcium levels, as these can be affected by progression to myeloma, although these specific tests are implied rather than explicitly detailed in the provided context.