The details of this cohort and their natural history have been described previously.8 (link) In brief, we identified 1395 persons with MGUS who resided in the 11 counties of southeastern Minnesota and who had a serum M protein concentration of 3 g per deciliter or less and 10% or fewer plasma cells in the bone marrow (if assessed). Patients with light-chain MGUS were not included, since this entity was defined after the establishment of the cohort at the inception of the study.9 (link) In accordance with our clinical practice, bone marrow examination was deemed unnecessary unless the patient had unexplained anemia, renal insufficiency, or bone pain. The patients were evaluated at the Mayo Clinic from January 1, 1960, through December 31, 1994. A total of 11 patients who had previously signed a form prohibiting review of their medical records for any type of research at the Mayo Clinic were excluded.8 (link),10 (link) Of the remaining 1384 patients, 514 (37%) resided in Olmsted County, which had a population of 92,006 persons in 1980, and the remaining 870 patients resided in the other counties of southeastern Minnesota (1980 population, 312,559 persons). The medical-records-linkage system of the Rochester Epidemiology Project11 (link) makes it possible to obtain complete case ascertainment among the residents of Olmsted County.
Follow-up included the review of each patient’s inpatient and outpatient medical records at the Mayo Clinic and the review of death certificates for patients who had died. Death certificates can be currently obtained from only 10 states; however, in almost all other patients we were able to ascertain survival status by contacting the patient’s family or primary care physician. For the purposes of this study, the follow-up of the original cohort was extended by more than 15 years to December 31, 2015; this change yielded an increase by a factor of 1.3 in the number of person-years of follow-up and in the number of observed progressions.
The M proteins were identified and quantitated by means of cellulose acetate or agarose-gel electrophoresis.12 If there was an abnormal band or equivocal pattern, immunoelectrophoresis or immunofixation was performed to confirm the presence of M protein and to ascertain the type. Patients were advised to undergo serum protein electrophoresis annually.
There was no commercial funding for this study. All the authors participated in the study concept, study design, and data collection; two of the authors conducted the data analysis. The authors vouch for the accuracy of the data and analyses presented and for the fidelity of the study to the protocol.
Follow-up included the review of each patient’s inpatient and outpatient medical records at the Mayo Clinic and the review of death certificates for patients who had died. Death certificates can be currently obtained from only 10 states; however, in almost all other patients we were able to ascertain survival status by contacting the patient’s family or primary care physician. For the purposes of this study, the follow-up of the original cohort was extended by more than 15 years to December 31, 2015; this change yielded an increase by a factor of 1.3 in the number of person-years of follow-up and in the number of observed progressions.
The M proteins were identified and quantitated by means of cellulose acetate or agarose-gel electrophoresis.12 If there was an abnormal band or equivocal pattern, immunoelectrophoresis or immunofixation was performed to confirm the presence of M protein and to ascertain the type. Patients were advised to undergo serum protein electrophoresis annually.
There was no commercial funding for this study. All the authors participated in the study concept, study design, and data collection; two of the authors conducted the data analysis. The authors vouch for the accuracy of the data and analyses presented and for the fidelity of the study to the protocol.
