Vertical cutoff methods in serum protein electrophoresis for the measurement of monoclonal protein concentrations: Which is best?

BACKGROUND: Monoclonal protein (M-protein) concentrations are measured by serum protein electrophoresis (SPE). Two methods are used for demarcating the M-protein area in the electropherogram: perpendicular drop (PD) and tangent skimming (TS). The aim of this study was tocompare both methods and to establish which is the most accurate and precise. METHODS: We studied 24 sera containing M-protein (5-44 g/L). The systematic error (SE) was evaluated in a dilution series of 12 sera. Within-day, between-day, and interobserver variability were assessed. SPE was performed by capillary and agarose gel electrophoresis. M-protein concentrations were measured using both cutoff methods. RESULTS: The PD method shows a constant SE ranged 1.00-2.27 g/L, while constant SE for TS is ranged -0.30--0.57 g/L. None of the cutoff methods or electrophoretic methods showed a proportional SE, with the exception of the TS method in capillary electrophoresis for ß-migrating M-protein. The PD method was more precise than the TS method in all three estimates of imprecision. An increased CV for concentrations < 10 g/L in between-day imprecision was observed with the TS method. Interobserver imprecision was greater for M-protein concentrations < 17 g/L for both cutoff methods (14.85%, 26.42% respectively). CONCLUSIONS: Despite being less precise, the TS method provides a more accurate measurement of M-protein concentration.

Estudio de la ferropenia en el laboratorio clínico / Laboratory evaluation of iron deficiency

El hierro es un elemento químico esencial para todos los organismos vivos, necesario para un amplio espectro de funciones metabólicas vitales. La exploración del metabolismo del hierro puede ser difícil en algunas situaciones, tales como en el paciente con una enfermedad crónica, por la respuesta de los biomarcadores frente a la inflamación. En los últimos años el laboratorio clínico ha incorporado nuevos biomarcadores a los tradicionalmente empleados, con el fin de mejorar su contribución al diagnóstico y seguimiento de la ferropenia. Se ha realizado una búsqueda sistemática de la evidencia científica publicada en los diez últimos años para los siguientes biomarcadores: el diagnóstico morfológico de la sangre periférica, los índices hematimétricos, y las concentraciones plasmáticas de transferrina (y sus índices), ferritina, receptor soluble de transferrina y hemoglobina, en la ferropenia. Se emiten recomendaciones para estos biomarcadores en relación al diagnóstico y manejo del paciente ferropénico

Iron is an essential chemical element for all living organisms, and is required for a broad spectrum of vital metabolic functions. The study of iron metabolism can be challenging in some situations, such as in patients with chronic diseases, due to the effect of inflammation response. In recent years, clinical laboratory research has introduced new biomarkers to those commonly used, with the aim of improving the diagnosis and management of iron deficiency. In this work, a systematic search of the scientific evidence reported during the last decade has been made for the following biomarkers: morphological diagnosis of peripheral blood, hematimetric indices, and plasma concentrations of transferrin (and its indices), ferritin, transferrin receptor, and haemoglobin, in iron deficiency. Recommendations are made for these biomarkers related to the diagnosis and management of the iron-deficient patient