47 ROC defined serum globulin cutoff as a screening tool for monoclonal gammopathies Punto de corte de globulinas por curva ROC para el tamizaje de gammapatías monoclonales Luz Tarín-Arzaga*, Omar Cantu-Martinez, Carlos de la Cruz-de la Cruz, Odra L. Martínez-González, Martha A. Reyes-López, José C. Jaime-Pérez, and David Gómez-Almaguer Hematology Service, Universidad Autónoma de Nuevo León, Facultad de Medicina y Hospital Universitario “Dr. José Eleuterio González,” Monterrey, Nuevo Leon, Mexico ORIGINAL ARTICLE Abstract Background: Serum protein electrophoresis (SPE), immunofixation, and free light chain assays are recommended for monoclonal gammopathy (MG) screening. High serum globulins might be an inexpensive and useful parameter to decide on a workup for MG. Objective: The objective of the study was to determine a serum globulin cutoff that predicts an abnor- mal SPE. Materials and methods: A retrospective, observational study performed in a hematological referral center. SPE, serum albumin, and globulins from patients with MG suspicion between January 2013 and August 2019 were collected. ROC curves for serum globulin and albumin/globulin ratio (A/G) were performed to identify their diagnostic yield for identifying the presence of M protein. Results: A total of 1578 SPE were collected; 1010 (64%) exhibited an M protein. After performing a ROC curve analysis, the best serum globulin value was ≥ 2.6 g/dL, with a sensitivity and specificity of 52% and 79.9%, respectively. Accordingly, the best A/G ratio cutoff (≤ 1.69) yielded a sensitivity of 58.9% and specificity of 79%. After a ROC curve sub-analysis on patients with an M protein ≥ 1 g/dL, the best serum globulin cutoff was ≥ 2.8 g/dL, with a sensitivity and specificity of 87.3% and 84.1%, respectively. The best A/G ratio cutoff was ≤ 1.38, with a sensitivity of 84.1% and spec- ificity of 88.6%. Conclusions: A serum globulin and/or A/G cutoff can be used to guide the clinical decision-making for early detection of MG and could decrease its underdiagnosis. This inexpensive laboratory testing strategy could be used to screen adult populations above the age of 50 in a cost-efficient way. Keywords: Monoclonal gammopathy. Globulin. Multiple myeloma. Screening. Serum protein electrophoresis. Resumen Antecedentes: La electroforesis de proteínas séricas (SPE), la inmunofijación y la medición de cadenas ligeras libres se recomiendan para la detección de gammapatía monoclonal (MG). Las globulinas séricas elevadas pueden ser útiles y menos costosas para considerar estudiar una MG. Objetivo: Determinar un límite de globulina sérica que prediga una SPE anormal. Material y métodos: Estudio observacional y retrospectivo, en un centro de referencia hematológico. Se recopila- ron SPE, albúmina sérica y globulinas de pacientes con sospecha de MG entre enero 2013 y agosto 2019. Se realizaron curvas ROC de globulina sérica y relación albúmina/globulina (A/G) para identificar su rendimiento diagnóstico para la presencia de proteína M. Resultados: Se recolectaron 1578 SPE; 1010 (64%) exhibieron una proteína M. Tras realizar un Correspondence: *Luz Tarín-Arzaga E-mail: tarinarzaga@gmail.com Available online: 22-06-2022 Medicina Universitaria. 2022;24(2):47-51 www.medicinauniversitaria.org Date of reception: 20-01-2022 Date of acceptance: 04-04-2022 DOI: 10.24875/RMU.22000004 1665-5796/© 2022 Universidad Autónoma de Nuevo León. Published by Permanyer. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Medicina Universitaria