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.

[Infection by Borrelia burgdorferi in patients with the human immunodeficiency virus. A diagnostic problem]. / Infección por Borrelia burgdorferi en pacientes infectados por el virus de la inmunodeficiencia humana. Un problema diagnóstico.

BACKGROUND: Given that Lyme's disease and HIV infection may present with similar clinical symptoms and that the serologic tests for the determination of antibodies against Borrelia burgdorferi present frequent false positives, the presence of antibodies against B. burgdorferi in patients with HIV in different evolutive stages was studied. METHODS: Antibodies against B. burgdorferi were determined by IFI and ELISA in a serum sample of 72 individuals with HIV. Western blot (WB) against B. burgdorferi was performed in the sera which were positive by one method or the other. The presence of antiphospholipid antibodies was also studied. RESULTS: A total of 24 sera (33%) were positive by IFI and/or ELISA. Twenty-one (29%) by IFI and 7 (10%) by ELISA (chi 2; p = 0.006). Four (5.5%) were positive by both methods. Only one of the sera was positive by IFI, ELISA and WB. No statistical relation was found upon comparison of the positive results against B. burgdorferi with the different evolutive stages of HIV infection or with the presence of antiphospholipid antibodies. CONCLUSIONS: The high prevalence of false positive serology to B. burgdorferi in the collective of patients with the human immunodeficiency virus infection together with the possibility of presenting similar clinical manifestations has led to extreme prudence in the diagnosis of infection by B. burgdorferi in patients with HIV infection.

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

Consensus document. Recommendations on assessing proteinuria during the diagnosis and follow-up of chronic kidney disease.

The presence of persistently elevated urinary concentrations of protein or albumin is considered a sign of kidney damage. The diagnosis and staging of chronic kidney disease (CKD) is nowadays based upon the presence of signs of kidney damage together with the estimation of the glomerular filtration rate.The presence of either proteinuria or albuminuria identifies a group of patients with higher risk of CKD progression and higher cardiovascular risk. Treatment with angiotensin converting enzyme inhibitors or angiotensin-receptor blockers,for instance, decreases both the progression of CKD and the incidence of cardiovascular events and death in patients with CKD and proteinuria. Thus, proteinuria is currently considered a therapeutic target by itself. Despite of the importance of detecting and monitoring proteinuria in the diagnosis and follow-up of CKD, there is not a consensus among the clinical practice guidelines published by different scientific societies on the diagnostic cut-off levels, on different sampling procedures,on the units used in laboratory reports or just on whether it should be defined in terms of albumin or proteinuria. The goal of this document, created by the consensus of the Spanish Society of Clinical Biochemistry and Molecular Pathology(SEQC, representing its spanish acronym) and the Spanish Society of Nephrology (S.E.N.), is to recommend to medical and laboratory clinicians appropriate guidelines for the detection and monitorization of proteinuria as a marker of CKD in adults and children. These recommendations result from searching,evaluating and summarizing current scientific evidence published in the last years.

Documento de Consenso. Recomendaciones sobre la valoración de la proteinuria en el diagnóstico y seguimiento de la enfermedad renal crónica / Consensus Document. Recommendations on assessing proteinuria during the diagnosis and follow-up of chronic kidney disease

La presencia de concentraciones elevadas de proteína o albúmina en orina, de modo persistente, es un signo de lesión renal y constituye, junto con la estimación del filtrado glomerular, la base sobre la que se sustenta el diagnóstico de la enfermedad renal crónica (ERC). Su presencia identifica a un grupo de pacientes con un riesgo superior de progresión de la enfermedad renal y con mayor morbilidad cardiovascular. El tratamiento con inhibidores de la enzima de conversión de la angiotensina o antagonistas del receptor de la angiotensina, en individuos con ERC y proteinuria, ha demostrado que disminuye tanto la progresión de la enfermedad renal como la incidencia de eventos cardiovasculares y muerte, por lo que la disminución del valor de la proteinuria es considerado un objetivo terapéutico. Pese a la importancia de la detección y monitorización de la proteinuria en el diagnóstico y seguimiento de la ERC, no existe consenso entre las guías de práctica clínica publicadas por distintas Sociedades científicas sobre cuáles son los valores que indican su presencia, si ésta debe ser definida en términos de albúmina o de proteína, el espécimen más adecuado para su medida o el tipo de unidades en que deben ser expresados los resultados. La finalidad de este documento, elaborado con el consenso de la Sociedad Española de Bioquímica Clínica y Patología Molecular (SEQC) y la Sociedad Española de Nefrología (S.E.N.), es proporcionar recomendaciones, a los facultativos clínicos y de laboratorio, para la detección y monitorización de la proteinuria como marcador de la presencia de ERC en adultos y en niños. Las recomendaciones son el resultado de la búsqueda, evaluación y síntesis de la evidencia científica publicada sobre el tema en los últimos años (AU)

The presence of persistently high urinary concentrations of protein or albumin is considered a sign of kidney damage. Nowadays, the diagnosis of chronic kidney disease (CKD) is based on the presence of signs of kidney damage together with the estimation of the glomerular filtration rate. The presence of either proteinuria or albuminuria identifies a group of patients with a higher risk of progression of CKD and higher cardiovascular risk. Treatment with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers decreases both the progression of CKD and the incidence of cardiovascular events and death in patients with CKD and proteinuria. Thus, proteinuria is currently considered a therapeutic target by itself. Despite the importance of detecting and monitoring proteinuria in the diagnosis and follow-up of CKD, there is no consensus among the clinical practice guidelines published by different scientific societies on the diagnostic cut-off levels, on different sampling procedures, on the units used in laboratory reports or just on whether it should be defined in terms of albuminuria or proteinuria. The goal of this document, created with the agreement of the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC, representing its Spanish acronym) and the Spanish Society of Nephrology (S.E.N.), is to recommend appropriate guidelines to medical and laboratory physicians for detecting and monitoring proteinuria as a marker of CKD in adults and children. These recommendations are the result of searching, evaluating and summarising current scientific evidence published in the last few years (AU)