Monoclonal Gammopathy of Undetermined Significance: Indications for Prediagnostic Testing, Subsequent Diagnoses, and Follow-up Practice at Mayo Clinic

Objectives: To determine the indications for prediagnostic testing, subsequent diagnoses found, and follow-up practices in patients who were incidentally diagnosed with monoclonal gammopathy of undetermined significance (MGUS). Patients and Methods: From our prospective MGUS database, we identified 329 patients residing in southeastern Minnesota who were diagnosed from January 1, 2011, through December 31, 2014, and followed up at Mayo Clinic. Results: Most test orders came from nonhematologists (n=310, 94.2%). The top 5 indications were neuropathy (n=65, 19.8%), renal disease (n=45, 13.7%), anemia (n=42, 12.8%), bone disorder or connective tissue pain (n=42, 12.8%), and cutaneous disease (n=19, 5.8%). Hypercalcemia was an infrequent indication (n=9, 2.7%). The final diagnosis for all neuropathy evaluations was sensory/motor neuropathy—not otherwise specified, with 18.7% having IgM MGUS. Chronic kidney disease—not otherwise specified, iron deficiency, and osteoporosis/osteopenia were the most common subsequent diagnoses for test indications of renal disease, anemia, and bone disorder or connective tissue pain, respectively. Most patients (n=213, 64.7%) had 1 or more follow-up visit during the study period. A minority were followed by hematologists (43.5%, n=143). Patients with low-risk MGUS comprised 45.0% (n=148) of the cohort. Male patients and younger patients were more likely to be followed up than their counterparts (P<.01). About one-third (n=27, 32.1%) of patients 80 years or older (n=84) continued to have regular follow-up visits. Hematologists were more likely to follow patients with MGUS more closely than nonhematologists (P<.001). However, the intensity of follow-up was not based on MGUS risk. Conclusion: Monoclonal protein testing is commonly performed for signs and symptoms not typically associated with lymphoplasmacytic malignancies. There is a significant variation in MGUS follow-up between hematologists and nonhematologists (P<.001) that is not based on risk factors or clinical practice guidelines.