ObjectiveTo investigate the characteristics and distribution of monoclonal gammopathy in clinical patients.

MethodsA total of 936 171 patients (508 449 males and 427 722 females) who received capillary zone electrophoresis in Zhongshan Hospital Affiliated to Fudan University from January 2012 to December 2021 were selected, from which 14 945 patients with abnormal bands were screened as the study subjects, including 10 173 males and 4 772 females and the age 21-102 (65±13) years old. According to the age, patients were divided into 8 groups: 21-30 years old (168 cases), 31-40 years old (405 cases), 41-50 years old (1 326 cases), 51-60 years old (3 068 cases), 61-70 years old (4 985 cases), 71-80 years old (3 288 cases), 81-90 years old (1 519 cases), and≥91 years old (186 cases). The diagnostic results of the 14 945 patients with abnormal bands were collected and were divided into tumor group (5 196 cases) and non-tumor disease group (9 749 cases) according to the presence of tumor. The distribution of abnormal bands in different gender, age, and disease groups were retrospectively analyzed. Among the 14 945 patients, 4 988 cases underwent immunofixation electrophoresis, excluding 336 negative cases and 412 cases of double clonal bands reaction, and 4 240 patients with monoclonal immunoglobulin (M protein) reaction were selected as the study subjects, including 2 794 males and 1 446 females aged 21-102 (67±12) years old. They were divided into 8 groups according to the age: 21-30 years old (18 cases), 31-40 years old (91 cases), 41-50 years old (364 cases), 51-60 years old (862 cases), 61-70 years old (1 455 cases), 71-80 years old (904 cases), 81-90 years old (486 cases), and≥91 years old (60 cases). The diagnostic results and immunoglobin subtypes (IgA-κ, IgA-λ, IgG-κ, IgG-λ, IgM-κ, IgM-λ, κ, λ) of patients were collected, and the distribution of monoclonal gammopathy in different gender, age and disease groups were retrospectively analyzed.

ResultsAmong 936 171 patients, 14 945 cases showed abnormal bands in electropherograms with a detection rate of 1.60%; the detection rates of abnormal bands in males and females were 2.00% (10 173/508 449) and 1.12% (4 772/427 722), respectively, with a statistically significant difference ( P<0.01). There was a significant difference in the detection rate of abnormal bands among different age groups ( P<0.01); among them, the highest detection rate of abnormal band in group of ≥91 years old was 5.98%, and the ratio of male to female was 1.67∶1. Among the 14 945 cases of abnormal bands, patients aged 51-60, 61-70 and 71-80 accounted for 20.53% (3 068 cases), 33.36% (4 985 cases) and 22.00% (3 288 cases), respectively, and the differences among the age groups were statistically significant (χ ²=115.82, P<0.01). In the tumor group, the top 3 tumors with abnormal bands were plasmacytoma with 1 123 cases, lymphoma with 289 cases, and leukemia with 49 cases. The detection rate of abnormal bands in electropherograms of plasmacytoma was 89.92% (1 123/1 249), which was higher than that in lymphoma and leukemia [6.73% (289/4 296) and 6.40% (49/766), respectively, P<0.01]. Among 4 240 patients with positive M protein, the proportion of 51-60, 61-70 and 71-80 years old patients were 20.33% (862/4 240), 34.32% (1 455/4 240) and 21.32% (904/4 240), respectively, and the differences among age groups were statistically significant ( P<0.01). The results of M protein types showed that the proportion of IgG-κ type was the highest in both genders, with 32.28% (902/2 794) in males and 34.30% (496/1 446) in females. In the 21-30, 31-40, and 41-50 age groups, the proportion of IgG-λ was the highest, which were 38.89% (7/18), 36.26% (33/91) and 34.07% (124/364) in these groups respectively. However, the proportions of IgG-κ were the highest in either of the 51-60, 61-70, 71-80, 81-90 and ≥91 years old groups, which were 33.87% (292/862), 34.16% (497/1 455), 31.53% (285/904), 34.57% (168/486), 28.33% (17/60), respectively, and the differences among all age groups and gender groups had statistical significance ( P<0.01). Among patients with positive M protein in the tumor group, plasmacytoma accounted for 14.22% (603/4 240), followed by lymphoma 6.30% (267/4 240); among non-tumor diseases, M proteinemia accounted for the highest proportion (7.24%, 307/4 240), followed by pulmonary infection (5.47%, 232/4 240).

ConclusionsThe detection rate of abnormal bands in capillary zone electrophoresis may increase with age, and is higher in males than in females in the same age group; different malignant tumor diseases can also show abnormal bands in capillary zone electrophoresis, but they are still mainly hematological tumors. Among the positive results of M protein, 61-70 years old group accounts for the highest proportion; the most common type of monoclonal gammopathy is IgG type; in the age group of 21-50 years, the proportion of IgG-λ type is the highest; in the group of >50 years old, the proportion of IgG-κ type is the highest; in the diagnosis of positive monoclonal gammopathy, the top 3 diseases are all hematological diseases, including plasmacytoma, monoclonal gammopathies and lymphoma.