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Clin Chem. 2011 Dec;57(12):1687-92. doi: 10.1373/clinchem.2011.171314. Epub 2011 Oct 6.

Long-term biological variation of serum protein electrophoresis M-spike, urine M-spike, and monoclonal serum free light chain quantification: implications for monitoring monoclonal gammopathies.

Author information

1
Division of Clinical Biochemistry & Immunology, Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN, USA. katzmann.jerry@mayo.edu

Abstract

BACKGROUND:

We analyzed serial data in patients with clinically stable monoclonal gammopathy to determine the total variation of serum M-spikes [measured with serum protein electrophoresis (SPEP)], urine M-spikes [measured with urine protein electrophoresis (UPEP)], and monoclonal serum free light chain (FLC) concentrations measured with immunoassay.

METHODS:

Patients to be studied were identified by (a) no treatment during the study interval, (b) no change in diagnosis and <5 g/L change in serum M-spike over the course of observation; (c) performance of all 3 tests (SPEP, UPEP, FLC immunoassay) in at least 3 serial samples that were obtained 9 months to 5 years apart; (d) serum M-spike ≥10 g/L, urine M-spike ≥200 mg/24 h, or clonal FLC ≥100 mg/L. The total CV was calculated for each method.

RESULTS:

Among the cohort of 158 patients, 90 had measurable serum M-spikes, 25 had urine M-spikes, and 52 had measurable serum FLC abnormalities. The CVs were calculated for serial SPEP M-spikes (8.1%), UPEP M-spikes (35.8%), and serum FLC concentrations (28.4%). Combining these CVs and the interassay analytical CVs, we calculated the biological CV for the serum M-spike (7.8%), urine M-spike (35.5%), and serum FLC concentration (27.8%).

CONCLUSIONS:

The variations in urine M-spike and serum FLC measurements during patient monitoring are similar and are larger than those for serum M-spikes. In addition, in this group of stable patients, a measurable serum FLC concentration was available twice as often as a measurable urine M-spike.

PMID:
21980167
PMCID:
PMC3736848
DOI:
10.1373/clinchem.2011.171314
[Indexed for MEDLINE]
Free PMC Article

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