SARS-CoV-2 infection is not associated with the emergence of monoclonal gammopathies.

BACKGROUND: Upon infection activated plasma cells produce large quantities of antibodies which can lead to the emergence of a monoclonal component (MC), detectable by serum protein electrophoresis (SPEP). This study aims to investigate any correlation between SARS-CoV-2 infection and MC development and, if identified, whether it persists during follow-up. METHODS: SPEPs of 786 patients admitted to hospitals between March 01 2020 and March 31 2022 were evaluated. Positive (SARS-CoV-2+) and negative (SARS-CoV-2-) patients to nasopharyngeal swab for SARS-CoV-2 by RT-PCR were included. The persistence/new occurrence of MC was investigated for all patients during follow-up. Patient groups were compared by chi-square analysis. RESULTS: MC was identified in 12% of all patients admitted to hospital, of which 28.7% were SARS-CoV-2+. The most common immunoglobulin isotype in both groups was IgG-k. There was no correlation between MC development and SARS-CoV-2 infection (p = 0.173). Furthermore, the risk of MC persistence in SARS-CoV-2-negative patients was revealed to be higher than in the SARS-CoV-2+ at follow-up (HR = 0.591, p = 0.05). CONCLUSIONS: Our study suggests that the detection of MC during SARS-CoV-2 infection is most likely due to the hyperstimulation of the humoral immune system, as also occurs in other viral infections.

Early screening of thalassemia in pregnant women in northern China by capillary electrophoresis for the determination of hemoglobin electrophoresis.

The objective of this study was to analyze the effectiveness of capillary electrophoresis detection of hemoglobin electrophoresis (HE) for the early screening of thalassemia. In the first choice, 974 pregnant women were selected for capillary electrophoresis to detect HE, which showed that 46 of them were abnormal (4.72%), including 16 cases with HbA2<2.5% and 28 cases with HbA2>3.5% and/or HbF≥2.0%. In one case each of HbH and HbBart's abnormal bands was found. The genotype test results showed the presence of thalassemia in 34 cases, using the genotype test results as the gold standard, after calculation it was seen that capillary electrophoresis for HE diagnosis of the occurrence of thalassemia had a sensitivity and specificity of 54.34% and 70.97% (P<0.05). These results suggest that in the screening of thalassemia in northern China, capillary electrophoresis for HE has good application and can be used as one of the routine screening tools, but further confirmation by genotype testing is still needed.

Evusheld, a SARS-CoV-2 spike protein-directed attachment inhibitor, appears in serum protein electrophoresis and immunofixation: a case study.

Serum protein electrophoresis (SPE) and immunofixation (IFE) assays are commonly used to diagnose and monitor patients with multiple myeloma (MM). Identifying analytical interferences in SPE and IFE caused by therapeutic monoclonal antibodies (tmAbs) can be challenging. Here we report the case of a 72-year-old male with a long history of relapsed immunoglobulin (Ig)G kappa MM. A follow-up SPE showed the original peak plus 2 additional cathode peaks. Immunofixation was ordered as a reflex test to investigate the new peaks that showed initial patient monoclonal IgG kappa in addition to 2 restricted bands of the IgG kappa type. Therapeutic monoclonal antibody interference was suspected and the patient's chart was reviewed. The patient was not on any antimyeloma monoclonal antibody therapy. However, preexposure prophylaxis therapeutic monoclonal antibodies tixagevimab plus cilgavimab (Evusheld) for severe acute SARS-CoV-2 was administered approximately 45 minutes before sample collection, which led to the identifiable spikes and correlated bands. After 2 days, the IgG kappa bands disappeared, confirming this therapy's effect on SPE and IFE. Therefore, clinical pathologists should be aware of when providers prescribe new monoclonal antibody therapy and become familiar with the position of commonly prescribed (tmAbs) therapies at their institutions.

[Causes of Abnormal Hemoglobin Electrophoresis].

OBJECTIVE: To investigate the possible causes of abnormal hemoglobin electrophoresis results. METHODS: The hemoglobin electrophoresis results of 5 696 patients in the First Affiliated Hospital of Chengdu Medical College from September 2018 to July 2021 were collected, and the abnormal results and clinical significance were analyzed. RESULTS: The results of 486 patients (accounting for 8.53%) were abnormal, of which 300 cases had increased HbA2, 135 cases had decreased HbA2, 44 cases had increased F alone, and 7 cases had abnormal hemoglobin bands. Among the 486 patients, 246 patients were thalassemia gene positive (the positive rate was 50.62%), including 29 cases of α thalassemia, 208 cases of ß thalassemia and 9 cases of αß thalassemia. Among the patients with elevated HbA2, 68.67% were detected ß thalassemia, 3.00% αß thalassemia, 9.33% were suspected to be caused by macrocytosis, 6.33% by thyroid dysfunction, and 12.67% by uncertainty of the method. Among the patients with reduced HbA2, 21.48% were detected α thalassemia, 60.00% iron deficiency anemia, 8.15% were suspected to be caused by thyroid dysfunction, and 10.37% by uncertainty of the method. Among the patients with elevated F alone, the results of thalassemia gene detection were negative, 40.91% of them were suspected to be caused by macrocytosis, 27.27% by hereditary persistence of fetal hemoglobin, 29.55% by special physiological condition of pregnant women, and 2.27% by hyperthyroidism. Abnormal hemoglobin bands were detected in 7 patients, including 4 cases of hemoglobin D, 2 cases of hemoglobin E, and 1 case of hemoglobin J. CONCLUSION: Thalassemia, iron deficiency anemia, macrocytosis such as megaloblastic anemia and non-severe aplastic anemia, thyroid dysfunction, hereditary persistence of fetal hemoglobin, abnormal hemoglobin diseases, the uncertainty of the method are all important causes of abnormal hemoglobin electrophoresis results. In clinical work, the patient's indicators should be comprehensively analyzed to determine the possible cause.

Reference intervals for erythrocyte parameters and hemoglobin electrophoresis parameters for young children in Guangxi.

BACKGROUND: Erythrocyte parameter analysis is the important means for diagnosis and treatment of hematological diseases, which are essential for screening of thalassemia in southern China combined with hemoglobin electrophoresis analysis. But little is known regarding the reference intervals (RIs) in healthy pediatrics in these two areas. METHODS: 95% RIs of erythrocyte parameters were calculated from 853 healthy preschoolers, aged from 1 days to <6 years, according to the C28-A3C guidelines of the Institute of Clinical and Laboratory Standards. To express the magnitude of sex and age variation, standard deviation ratio (SDR) was calculated using ANOVA. Concurrently, we selected 3814 thalassemia carriers as carriers group and drew receiver operating characteristic (ROC) curves to establish the optimal cut-off values of hemoglobin electrophoresis parameters, which were used as the upper/lower limits of RIs to efficiently screen thalassemia. RESULTS: All parameters except red blood cell (RBC) required age partitioning, confirmed by SDRage above .4. There was no need for sex partitioning on all parameters, confirmed by SDRsex below .4. The optimal cut-off value of Hemoglobin A2 (Hb A2) in the four subgroups was <7.8% (Hb A), 2.3%-3.2%, 2.5%-3.6% and 2.6%-3.6%, respectively. CONCLUSION: In this study, the establishment of RIs improved the diagnostic efficiency of hematological disease (especially thalassaemia) for children in Guangxi. It provides reliable hematological references for the identification and diagnosis, treatment monitoring, and health screening of children's clinical diseases.

Causes of Abnormal Hemoglobin Electrophoresis / 中国实验血液学杂志

OBJECTIVE@#To investigate the possible causes of abnormal hemoglobin electrophoresis results.@*METHODS@#The hemoglobin electrophoresis results of 5 696 patients in the First Affiliated Hospital of Chengdu Medical College from September 2018 to July 2021 were collected, and the abnormal results and clinical significance were analyzed.@*RESULTS@#The results of 486 patients (accounting for 8.53%) were abnormal, of which 300 cases had increased HbA2, 135 cases had decreased HbA2, 44 cases had increased F alone, and 7 cases had abnormal hemoglobin bands. Among the 486 patients, 246 patients were thalassemia gene positive (the positive rate was 50.62%), including 29 cases of α thalassemia, 208 cases of β thalassemia and 9 cases of αβ thalassemia. Among the patients with elevated HbA2, 68.67% were detected β thalassemia, 3.00% αβ thalassemia, 9.33% were suspected to be caused by macrocytosis, 6.33% by thyroid dysfunction, and 12.67% by uncertainty of the method. Among the patients with reduced HbA2, 21.48% were detected α thalassemia, 60.00% iron deficiency anemia, 8.15% were suspected to be caused by thyroid dysfunction, and 10.37% by uncertainty of the method. Among the patients with elevated F alone, the results of thalassemia gene detection were negative, 40.91% of them were suspected to be caused by macrocytosis, 27.27% by hereditary persistence of fetal hemoglobin, 29.55% by special physiological condition of pregnant women, and 2.27% by hyperthyroidism. Abnormal hemoglobin bands were detected in 7 patients, including 4 cases of hemoglobin D, 2 cases of hemoglobin E, and 1 case of hemoglobin J.@*CONCLUSION@#Thalassemia, iron deficiency anemia, macrocytosis such as megaloblastic anemia and non-severe aplastic anemia, thyroid dysfunction, hereditary persistence of fetal hemoglobin, abnormal hemoglobin diseases, the uncertainty of the method are all important causes of abnormal hemoglobin electrophoresis results. In clinical work, the patient's indicators should be comprehensively analyzed to determine the possible cause.

[Detection of paraprotein in plasma cell tumors].

Paraprotein is a laboratory biomarker of plasma cell tumors and other lymphoproliferative diseases. Its determination is necessary for diagnosing, monitoring and assessment of therapy effectiveness. The lecture presents the main methods of qualitative and quantative analysis of monoclonal proteins: gel electrophoresis, capillary electrophoresis, immunofixation and nephelometry features, possibilities and limitations are reviewed. The main sources of errors and artifacts during these studies are considered. Also the difficulties in the diagnosis and interpretation of the results of serum and urine tests are highlighted.

HemoTypeSC point-of-care testing shows high sensitivity with alkaline cellulose acetate hemoglobin electrophoresis for screening hemoglobin SS and SC genotypes

ABSTRACT Introduction: By providing timely actionable results for prompt management, point-of-care testing (POCT) kits have revolutionised medical care for various diseases, ranging from infectious diseases like malaria to genetic disorders, such as sickle cell disease (SCD). They are, however, underutilised in the diagnosis of SCD in developing countries, where the need is greatest. Objective: The study was aimed at assessing the sensitivity of HemoTypeSC POCT among a cohort of children with SCD, previously diagnosed by Alkaline cellulose acetate hemoglobin electrophoresis (ACAE), with or without high-performance liquid chromatography (HPLC). Methods: In this descriptive cross-sectional study, HemoTypeSC test was conducted on all participants and its sensitivity was determined by comparing results with those obtained using ACAE. Discordance was verified with HPLC. Results: One hundred and forty-five children aged one to 19 years were studied. There were 84 males and 61 females (male: female ratio = 1.4:1). The HemoTypeSC was able to correctly diagnose sickle cell anemia (SCA) and hemoglobin SC in all (100%) of the children tested. Conclusion: The HemoTypeSC shows high sensitivity in detecting SCA and hemoglobin SC. Hence, it is useful for targeted screening of individuals suspected of having SCD, leading to rapid diagnosis of these hemoglobinopathies, even in resource-constrained settings.

Valor diagnóstico de la electroforesis de proteínas y cadenas ligeras libres en suero en el mieloma múltiple / Diagnostic value of serum protein electrophoresis and free light chains in the multiple myeloma's diagnosis

RESUMEN Fundamento: La electroforesis de proteínas y las cadenas ligeras libres en suero son técnicas utilizadas en el diagnóstico del mieloma múltiple. Sin embargo, la utilidad diagnóstica de ambas pruebas puede variar según el método empleado y condiciones reales del medio donde se realicen. Objetivo: Determinar el valor diagnóstico de la electroforesis de proteínas y de las cadenas ligeras libres en suero en el mieloma múltiple. Metodología: Se realizó un estudio retrospectivo de los parámetros electroforesis de proteínas en suero y cadenas ligeras libres en suero a 43 pacientes con diagnóstico de mieloma múltiple por evaluación de la médula ósea. La electroforesis de proteínas se realizó por el método convencional de separación de proteínas sobre papel de acetato de celulosa y para las cadenas ligeras libres se aplicó un ensayo inmunoturbidimétrico en el que se usó un analizador químico (Cobas 311). Se calcularon 7 parámetros que evaluaron la exactitud diagnóstica. Resultados: Todos los parámetros que evaluaron la exactitud diagnóstica estuvieron dentro de los intervalos de confianza en ambas pruebas. Conclusiones: La electroforesis de proteínas y las cadenas ligeras libres en suero son ensayos de gran utilidad en el diagnóstico del mieloma múltiple y se deben utilizar en conjunto para la mayor captación posible de casos.

ABSTRACT Background: Protein electrophoresis and serum free light chains are techniques used in the diagnosis of multiple myeloma. However, the diagnostic utility of both tests may vary according to the method used and the actual conditions of the environment where they are performed. Objective: To determine the diagnostic value of protein electrophoresis and serum free light chains in multiple myeloma. Methodology: A retrospective study of serum protein electrophoresis parameters and serum free light chains was conducted in 43 patients diagnosed with multiple myeloma by bone marrow evaluation. Protein electrophoresis was completed by the conventional method of protein separation on cellulose acetate paper and for free light chains an immunoturbidimetric assay was applied in which a chemical analyzer (Cobas 311) was used. Seven parameters were calculated to evaluate diagnostic accuracy. Results: All parameters assessing diagnostic accuracy were within confidence intervals in both tests. Conclusions: Protein electrophoresis and serum free light chains are very useful assays in the diagnosis of multiple myeloma and should be used in conjunction for the highest possible approval of cases.

Dual detection high-speed capillary electrophoresis for simultaneous serum protein analysis and immunoassays.

Serum protein electrophoresis (SPE) separates serum proteins into bands whose shape and amplitude can alert clinicians to a range of disorders. This is followed by more specific immunoassays to quantify important antigens and confirm a diagnosis. Here we develop a high-speed capillary electrophoresis (HSCE) platform capable of simultaneous SPE and immunoassay measurements. A single laser excitation source is focused into the detection zone of the capillary to measure both refractive index (SPE) and fluorescence signals (immunoassays). The refractive index signal measures characteristic SPE profiles for human serum separated in 100 mM boric acid (pH 10), 100 mM arginine (pH 11), and 20 mM CHES (pH 10). For the immunoassay, the fluorescence electropherograms reveal that CHES provides the optimal buffer for measuring the immunocomplex and separating it from the free antigen. Immunoassays in CHES yield a LOD of 23 nM and a LOQ of 70 nM for the detection of fluorescein. The high pH reduces protein adsorption but reduces antibody affinity. Preliminary studies carried out in 50 mM barbital at pH 8 show improved stability of the immunocomplex and better separation for immunoassay quantification. Further optimization will open new capabilities for measuring orthogonal diagnostic signals in seconds with HSCE.

To skim or splice? Comparing the quantification of M-proteins using two peak-integration protocols across multiple electrophoresis platforms.

OBJECTIVES: M-protein quantification by peak integration in serum protein electrophoresis (SPE) plays a central role in diagnosing, prognosing and monitoring monoclonal gammopathies. The conventional perpendicular drop (PD) integration approach integrates M-spikes from the baseline, which performs acceptably when the M-protein concentration is relatively high compared to the amount of background proteins present. The alternative peak-integration protocol by tangential skim (TS), however, allows for more accurate M-protein estimations by excluding background proteins. Despite some guideline recommendations, TS has been poorly adopted, making an understanding of the differences between the two protocols and their potential impacts paramount when considering a change from PD to TS. DESIGN & METHODS: We conducted retrospective investigations of the differences in M-protein quantification over large concentration ranges between PD and TS on 3 of the most popular electrophoresis platforms. RESULTS: Compared to PD, TS gave consistently lower results; the differences between the two methods increased tremendously and became more sporadic as M-protein concentrations dropped below 15 g/L in all 3 platforms. At < 15 g/L, the average % difference ranged from -81 % to -95 %, while above 15 g/L, the average % difference was only -13 to -31 %. Medical decision point analyses using linear regression predicted statistically significant and platform-dependent differences, which could impact clinical interpretation. CONCLUSIONS: Careful consideration of the magnitude of concentration changes and the potential impacts on patient classification and management should be made when switching to TS for M-protein quantification.

Detection of Plasma Cell Disorders by Mass Spectrometry: A Comprehensive Review of 19,523 Cases.

OBJECTIVES: To verify the analytical performance of a new mass spectrometry-based method, termed MASS-FIX, when screening for plasma cell disorders in a routine clinical laboratory. PATIENTS AND METHODS: Results from 19,523 unique patients tested for an M-protein between July 24, 2018, and March 6, 2020, by a combination serum protein electrophoresis (SPEP) and MASS-FIX were examined for consistency with pretest implementation performance. MASS-FIX's ability to verify abnormal results from SPEP and free light chain measurements was then compared with that of immunofixation electrophoresis (IFE) using a separate cohort of 52,586 patients tested by SPEP/IFE during the same period. RESULTS: Overall, 62.4% of our cohort was negative for an M-protein. Importantly, 7.3% of all specimens had an M spike on SPEP (0.1 to 8.5 g/dL) and MASS-FIX detected an M-protein in all these samples. Of all samples, 30.3% had M-proteins that were detected by MASS-FIX but the SPEP finding was too small for quantification. Of the positive samples, 5.7% contained a therapeutic monoclonal antibody. Of the positive samples, 4.1% had an N-glycosylated light chain (biomarker of high-risk plasma cell disorders). MASS-FIX confirmed a higher percentage of SPEP abnormalities than IFE. MASS-FIX was slightly more sensitive than IFE when confirming an M-protein in samples with an abnormal free light chain ratio. MASS-FIX had a very low sample repeat rate (1.5%). MASS-FIX was highly automatable resulting in a higher number of samples/technologist/day than IFE (∼30% more). CONCLUSION: Overall, MASS-FIX was successful in maintaining validation characteristics. MASS-FIX was more sensitive in confirming SPEP abnormalities when compared with IFE. Ability to detect therapeutic monoclonal antibodies and glycosylated light chains was distinctly advantageous.

Accurate Quantification of Monoclonal Immunoglobulins Migrating in the Beta Region on Protein Electrophoresis.

BACKGROUND: The concentration of monoclonal immunoglobulins (Igs) in neoplastic monoclonal gammopathic manifestations is generally measured by densitometric scanning of the monoclonal peaks on gel or by measuring absorbance at 210 nm in capillary electrophoresis (CE). For monoclonal Igs migrating in the beta region, measurement is complicated by the major beta-region proteins, namely, transferrin and C3. METHODS: C3 interference in densitometry was eliminated by heat treatment of serum, and monoclonal Igs were quantified by densitometry of the residual band. The immunochemical measurement of transferrin was converted to its equivalent densitometric quantity. For monoclonal Ig migrating with transferrin, the contribution of the latter was removed by subtracting the converted transferrin concentration from the combined densitometric quantification of the band. With CE, monoclonal Ig was measured by using immunosubtraction (ISUB) to guide demarcation. RESULTS: The results obtained using the C3 depletion and transferrin subtraction method were lower and yet comparable to the results derived from using CE measurement guided by ISUB. As we expected, the results from both methods were lower than those derived from a perpendicular drop measurement of the peak or via nephelometric assay of the involved isotype. DISCUSSION: Accurate measurement of monoclonal Igs is important for the diagnosis and monitoring of monoclonal gammopathic manifestations. Determination of serum free light chain concentration per gram of monoclonal Ig is an essential measure for the diagnosis of light chain-predominant multiple myeloma. The method described herein improves accuracy of measurements for monoclonal Igs migrating in the beta region, without the need for special reagents or equipment.

Application of an optimized interpretation model in capillary hemoglobin electrophoresis for newborn thalassemia screening.

INTRODUCTION: Newborn screening is an important supplement to thalassemia control and prevention. Capillary electrophoresis (CE) technology has several advantages for thalassemia screening but with low sensitivity, especially for thalassemia carriers. This study aims to illustrate the application of an optimized interpretation model in newborn thalassemia screening by capillary hemoglobin electrophoresis. METHODS: Two thousand, two hundred fifty-eight neonates selected from four regions in China were enrolled and were screened for α-thalassemia and ß-thalassemia by capillary electrophoresis. Results were interpreted based on an optimized model integrated with multiple parameters. Molecular analysis was carried out in synchrony and used as the gold standard for the screening performance assessment. The consistency among different regions and thalassemia genotypes were also investigated. RESULTS: Among the 2258 neonates, 485 were identified to have a likely diagnosis of thalassemia, and 422 α-thalassemia, 80 ß-thalassemia, and 21 α/ß-thalassemia cases were confirmed by molecular analysis, including 277 α-thalassemia silent carriers, 135 α-thalassemia trait carriers, 10 Hemoglobin H disease, and 80 ß-thalassemia trait carriers. The screening sensitivity, specificity, positive, and negative predictive value for α-thalassemia and ß-thalassemia were 84.83%, 99.14%, 95.98%, 96.41%, and 88.75%, 98.73%, 76.34%, and 99.48%, respectively. The optimized interpretation model showed higher performance for thalassemia carriers, though some neonates with silent α-thalassemia genotypes (-α3.7 /αα, -α4.2 /αα, and αWS α/αα) and ß-28 /ßN genotype were still missed. The screening performance among different regions was comparable. CONCLUSIONS: Capillary hemoglobin electrophoresis with the optimized interpretation model shows reliable performance for newborn thalassemia screening. It is applicable to large-scale population screening.

Reflexing Suspicious ß-Region Findings on Capillary Serum Protein Electrophoresis to Immunofixation or Immunosubtraction for Detecting Monoclonal Proteins.

OBJECTIVES: Monoclonal immunoglobulins (M-proteins) that migrate in the ß region on serum protein electrophoresis (SPEP) are often cloaked by this region's normal constituents. The present study interrogates the utility of using both quantitative and qualitative alterations in ß-region bands for detection of ß-migrating M-proteins. METHODS: Consecutive SPEP cases analyzed by capillary electrophoresis were searched to identify the initial workup on 1,841 patients with increased total ß regions, suspicious ß-region findings resulting in reflex immunofixation (IFE), or immunosubtraction (ISUB). To augment quantitative information, separate ß1 and ß2 measurements were established and retrospectively used to evaluate their sensitivity for M-protein detection. RESULTS: We identified M-proteins in 205 (11.1%) cases, including immunoglobulin A (IgA) (54%), IgG (24%), IgM (13%), and free light chain (9%) isotypes. Of the 15 cases flagged by separate ß1 and ß2 measurements that were not identified by total ß-region measurement, 1 progressed to myeloma. Of the 56 ß-migrating M-proteins identified by qualitative features but without increase in any of the ß-region measurements, 1 progressed to myeloma. CONCLUSIONS: A combination of separate measurements for ß1 and ß2 regions together with detection of ß-region distortions increase sensitivity for identifying ß-migrating M-proteins via reflex IFE or ISUB.

Valor diagnóstico de la electroforesis de proteínas y cadenas ligeras libres en suero en el mieloma múltiple / Diagnostic value of serum protein electrophoresis and free light chains in the multiple myeloma's diagnosis

Fundamento: La electroforesis de proteínas y las cadenas ligeras libres en suero son técnicas utilizadas en el diagnóstico del mieloma múltiple. Sin embargo, la utilidad diagnóstica de ambas pruebas puede variar según el método empleado y condiciones reales del medio donde se realicen. Objetivo: Determinar el valor diagnóstico de la electroforesis de proteínas y de las cadenas ligeras libres en suero en el mieloma múltiple. Metodología: Se realizó un estudio retrospectivo de los parámetros electroforesis de proteínas en suero y cadenas ligeras libres en suero a 43 pacientes con diagnóstico de mieloma múltiple por evaluación de la médula ósea. La electroforesis de proteínas se realizó por el método convencional de separación de proteínas sobre papel de acetato de celulosa y para las cadenas ligeras libres se aplicó un ensayo inmunoturbidimétrico en el que se usó un analizador químico (Cobas 311). Se calcularon 7 parámetros que evaluaron la exactitud diagnóstica. Resultados: Todos los parámetros que evaluaron la exactitud diagnóstica estuvieron dentro de los intervalos de confianza en ambas pruebas. Conclusiones:La electroforesis de proteínas y las cadenas ligeras libres en suero son ensayos de gran utilidad en el diagnóstico del mieloma múltiple y se deben utilizar en conjunto para la mayor captación posible de casos [AU]

Method comparison for serum protein electrophoretic M-protein quantification: Agarose gel electrophoresis and capillary zone electrophoresis in canine and feline sera.

BACKGROUND: Densitometric quantification of myeloma paraproteins (M-proteins) is used to monitor secretory myeloma related disorders in humans and dogs. The previous work in dogs used agarose gel electrophoresis (AGE) but did not establish if other methods of serum protein electrophoresis, such as capillary zone electrophoresis (CZE), were comparable. OBJECTIVES: We aimed to determine if the densitometric quantification of M-proteins using CZE would yield results comparable to AGE methods. METHODS: Fifty-one serum samples from 22 dogs and 18 cats with confirmed monoclonal gammopathies and previously performed AGE were evaluated using CZE on a Sebia Minicap system. Samples were run in duplicate, and their M-proteins were densitometrically measured using the corrected perpendicular drop method previously described. Human-based quality control samples were used to determine the inter-run coefficient of variation (CV). Patient samples were used to calculate the intra-run CV. Method comparison was performed using simple linear regression, Passing-Bablok regression, and Bland-Altman analyses, and Medx evaluations. RESULTS: Inter-run and intra-run CVs for CZE were 3.71%-7.65% and 2.89%-4.74%, respectively. Simple linear regression demonstrated an excellent correlation (r > 0.98). Passing-Bablok regression was compatible with the presence of proportional bias in the entire population, and Bland-Altman plots revealed a proportional bias in the feline cases. The Medx evaluation suggested that the two methods did not perform similarly in clinical samples with poor performance at a decision limit of 0.5 gm/dL. CONCLUSIONS: Capillary zone electrophoresis is an acceptable method for M-protein densitometric quantification in canine and feline sera but cannot be used interchangeably with AGE-based evaluations.