• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • SSMGMS - Mass spectrometry MGUS raw result
  • SSMGMSI - Mass spectrometry MGUS interpretation
  • SSMGMSF - Comb mass spec and IF MGUS raw result
  • SSMGMSFI - Comb mass spec and IF MGUS interpretatio

National Health and Nutrition Examination Survey

1988-1994 Data Documentation, Codebook, and Frequencies

Monoclonal gammopathy of undetermined significance (MGUS) mass spectrometry - Serum (Surplus) (SSNH3MGM)

Data File: SSNH3MGM.xpt

First Published: February 2025

Last Revised: NA

Component Description

Monoclonal gammopathies (also referred to as monoclonal immunoglobulins, monoclonal proteins, or M proteins) are conventionally detected by serum protein electrophoresis and serum protein immunofixation. Monoclonal gammopathies represent identical antibodies made by a clone of plasma cells and are detected in patients with multiple myeloma and its precursor condition, monoclonal gammopathy of undetermined significance (MGUS).

Mass spectrometry is a new, more sensitive and specific method to identify monoclonal proteins. Mass spectrometry used to detect monoclonal gammopathies has been referred to as MASS-FIX. In addition to improved sensitivity and specificity, mass spectrometry can also be used to identify antibodies used in treatment that can be accurately identified in patients, and distinguished from monoclonal proteins associated with MGUS and myeloma.

Using mass spectrometry can enable detection of monoclonal gammopathies even in people who are negative using conventional serum protein electrophoresis and immunofixation. The test provides a positive/negative result on whether a monoclonal gammopathy is present; and if present, also identifies the heavy and light chain subtype of the monoclonal gammopathy, such as IgG kappa, IgG lambda, or IgA kappa.

Eligible Sample

All NHANES III (1988-1994) MEC-examined and home-examined participants aged 10 to 49 years were eligible.

Description of Laboratory Methodology

Serum samples were batched and loaded onto a liquid handler along with reagents and a barcoded sample plate. The pre-analytical steps included:

(1) Plating immuno purification beads.

(2) Adding 10 μl of serum.

(3) Bead washing.

(4) Eluting the immunoglobulins (Igs), and reducing to separate the heavy and light Ig chains.

The resulting plate was transferred to a second low-volume liquid handler for matrix assisted laser desorption ionization (MALDI) plate spotting. Matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectra were collected. Integrated in-house developed software was utilized for sample tracking, driving data acquisition, data analysis, history tracking, and result reporting. Complete details of the methods are detailed by Kohlhagen et. al. (Kohlhagen et. al., 2020).

Results are reported as monoclonal protein PRESENT or ABSENT, and if PRESENT, the type of monoclonal gammopathy is also provided. Inadequate samples or equivocal results are denoted as INDETERMINATE.

Laboratory Quality Assurance and Monitoring

Stored serum specimens were shipped to the Protein Immunology Laboratory at Mayo Clinic, Rochester, Minnesota.

Data Processing and Editing

Data were received after all analyses were complete. The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Specific variables and edits:

SSMGMS: Mass spectrometry raw result for monoclonal gammopathy of undetermined significance

This variable denotes reported mass spectrometry results. The data were not edited.

SSMGMSI: Mass spectrometry interpretation for monoclonal gammopathy of undetermined significance

This variable is a summary interpretation of SSMGMS. Participants with a value of “1” (absent) for SSMGMS are coded as “1” (absent). Participants with a value of “5” through “20” are coded as “2” (present). Participants with a value of “2” (quantity not sufficient), “3” (indeterminate), or “4” (repeat) for SSMGMS are coded as “3” (indeterminate). Participants with a value of “missing” for SSMGMS are coded as “missing”.

SSMGMSF: Combined mass spectrometry and immunofixation raw result for monoclonal gammopathy of undetermined significance

This variable is a combined report of mass spectrometry results from SSMGMS and SSMGMSI and immunofixation results (refer to the SSNH3UOL Documentation for a description of immunofixation methods). When SSMGMSI is “1” (absent) or “3” (indeterminate), immunofixation results, if present, are instead provided.

SSMGMSFI: Combined mass spectrometry and immunofixation interpretation for monoclonal gammopathy of undetermined significance

This variable is a summary interpretation of SSMGMSF. Participants with a value of “1” (absent) for SSMGMSF are coded as “1” (absent). Participants with a value of “5” through “20” are coded as “2” (present). Participants with a value of “2” (quantity not sufficient), “3” (indeterminate), or “4” (repeat) for SSMGMSF are coded as “3” (indeterminate). Participants with a value of “missing” for SSMGMSF are coded as “missing”.

Analytic Notes

Refer to the NHANES III Laboratory Data File Documentation for general information on NHANES laboratory data.

There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. Additionally, availability of specimens for surplus projects is lower than for other laboratory tests performed on NHANES participants. The specimen availability can also vary by age or other population characteristics. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.

Please refer to the NHANES Analytic Guidelines for further details on the use of sample weights and other analytic issues.

Sample Weights, Demographics, and Other Related Variables

The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES III Laboratory Data File contains sample weights, demographic data, health indicators, and other related information collected during household interviews as well as the sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDPSTRA6 and SDPPSU6, respectively) in the laboratory data file. Additionally information on these variables and variables for subsets (such as NHANES III Phase I and NHANES III Phase II) can be found in the NHANES III Laboratory Data File Documentation.

This laboratory data file can be linked to the other NHANES III data files using the unique survey participant identifier (i.e., SEQN).

References

• Kohlhagen M., Dasari S., Willrich M., et al. Automation and validation of a MALDI-TOF MS (Mass-Fix) replacement of immunofixation electrophoresis in the clinical lab. Clin. Chem. Lab. Med. (2020) 59(1): 155-163.

Codebook and Frequencies