To compare the distribution differences of serum protein electrophoresis (SPE) among different gender and age individuals, and to explore the clinical application of SPE screening monoclonal gammopathy.

A retrospective analysis was conducted based on the SPE results obtained from 533 989 cases enrolled from January 2018 to December 2019 at Zhongshan Hospital Affiliated to Fudan University. Among these patients, 435 479 inpatients were from departments of hematology, nephrology, spinal surgery, endocrinology, and rheumatology and immunology; and 98 510 were apparently healthy individuals. The distributions of albumin, α1 globulin, α2 globulin, β1 globulin, β2 globulin and γ globulin in different gender and age groups (≤20, 21-30, 31-40, 41-50, 51-60, 61-70, 71-80, 81-90, ≥91 years old) were compared. A total of 10 014 cases were selected by immunofixation electrophoresis (IFE). The positive detection rates of different SPE bands and IFE bands were analyzed. The sensitivity and specificity of SPE methods were determined according to IFE results as the gold standard.

No significant difference was examined in the proportion of SPE bands between different genders (P>0.05). There were statistically significant differences in the proportion of albumin bands between apparently healthy individuals and hospitalized patients at different ages (apparently healthy individuals: F=5.12, P<0.05, inpatients: F=4.18, P<0.05), and all of them decreased with the increase of age. The proportion of γ globulin bands increased with age (apparently healthy individuals: F=1.34, P<0.05; inpatients: F=1.24, P<0.05). The sensitivity of SPE was 69% (2 098/3 051), and the specificity was 97% (6 721/6 963). Compared with IFE method, the positive detection rate of monoclonal gammopathy was significantly different (χ²=5 049.94, P<0.05). The positive rate of monoclonal gammopathy in γ globulin region (21.11%, 2 114/10 014) was higher than that in β globulin region (3.28%, 328/10 014) (χ²=90.74, P<0.05) and β-γ globulin region (1.63%, 163/10 014) (χ²=44.34, P<0.05). IgG and IgM bands are common in γ globulin region. Among them, IgG-κ type accounted for 94.1% (995/1 058), IgG-λ type accounted for 94.8% (690/728), IgM-κ type accounted for 89.2% (222/249), IgM-λ accounted for 83.8% (62/74). IgA bands are common in β region, of which IgA-κ accounted for 49.8% (103/207) and IgA-λ accounted for 51.6% (149/289). The positive rate of monoclonal gammopathy of IgG-κ type was the highest (10.57%, 1 058/10 014), and the positive rate of monoclonal gammopathy of IgM-λ type was the lowest (0.74%, 74/10 014).

With increasing age, the proportion of albumin band in SPE decreased and the proportion of γ globulin band increased. IgG and IgM type monoclonal gammopathy is mostly found in the gamma region, with a higher detection rate in IgG type. IgA type monoclonal gammopathy is mostly found in the β region, with a lower detection rate.

Blood protein electrophoresis; Immunoelectrophoresis; Monoclonal gammopathy