PCD diagnosis at screening will be determined as a nominal categorical variable indicating the participant's PCD diagnosis at screening. The categorical variable will include the following factor levels: monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), multiple myeloma (MM), AL amyloidosis, other PCD/ lymphoproliferative disorder, monoclonal gammopathy with unknown diagnosis, or no monoclonal gammopathy. Reason for unknown diagnosis may be due to non-definitive results, no results due to lab error, sampling issues, or participant did not get complete diagnostic work up.

PCD diagnosis during follow-up will be determined as a categorical variable for each new PCD diagnosis indicating whether the participant had the type of PCD diagnosed over the course of the follow up period on the study. The types of new PCD diagnosis will include SMM, MM, AL amyloidosis, and other PCD diagnosis, per diagnostic criteria as defined in Appendix A. Date of each new PCD diagnosis will also be captured.

CRAB criteria at MM diagnosis are defined as a binary variable indicating whether the participant had CRAB criteria at the time of MM diagnosis. CRAB criteria include hypercalcemia, renal insufficiency, anemia, or bone lesions as defined per IMWG. This will be evaluated only in the subjects diagnosed with MM during longitudinal follow-up

Time to MM diagnosis is defined as the duration of time from MGUS diagnosis (or SMM diagnosis for participants diagnosed with SMM at screening) to diagnosis of MM per IMWG criteria. The date of MM diagnosis is the date of the first assessment that identified MM. If the participant died without a diagnosis of MM, time to MM diagnosis will be calculated at the date of death, with death as a competing risk event. For surviving subjects who do not have documented MM diagnosis, time to MM diagnosis will be censored at the date of the last documented disease evaluation that confirmed no MM diagnosis.

Interaction with a community champion will be captured for each potential participant as a binary variable indicating whether or not the potential participant interacted with a study-associated community champion prior to enrollment or prior to declining participation. This will be captured via the "Interaction with Community Champion Survey".

Community champion impact will be reported by each enrolled participant that interacted with a community champion. It will be captured as an ordered categorical variable (5-point Likert scale) indicating the level of impact that the community champion had on the participant's decision to participate in the study. This will be captured via the "Interaction with Community Champion Survey".

For each participant that is determined to have MGUS at screening, a binary variable will be captured, indicating whether or not the participant consented to be followed longitudinally in the longitudinal portion of the study.

For participants who are approached but do not verbally agree to participation in the study, verbal reason for declining study participation will be reported and captured via a "Barriers to Participation Survey" that includes multi-select discrete options as well as an "Other" reason with free text option.

For participants with monoclonal gammopathy identified during screening but who do not agree to participate in the longitudinal portion of the study, reason for declining longitudinal participation will be reported and captured via a "Barriers to Participation Survey" that includes multi-select discrete options as well as an "Other" with free text option.

For each participant with monoclonal gammopathy identified during screening, a binary variable indicating whether a psychological counseling referral was accepted after learning of positive results.

Determined as a binary variable indicating whether the participant had light chain MGUS diagnosis at screening. Three definitions of light chain MGUS (with applicable reference ranges for FLC ratio, involved FLC) will be utilized to evaluate this endpoint: standard IMWG diagnostic criteria [with FLC ranges from Katzmann et al (2002)], iStop MM criteria incorporating age and renal function [Long et al (2025)], and Dana Farber Cancer Institute criteria incorporating race [Bertamini et al (2025)].