Estado actual de la medida de hemoglobina A1c y objetivos para su mejora: del caos al orden para mejorar la atención de la diabetes / Status of Hemoglobin A1c measurement and goals for improvement: from chaos to order for improving diabetes care

El Estudio de Control y Complicaciones de la Diabetes (DCCT) y el Estudio Prospectivo de Diabetes en el Reino Unido (UKPDS) establecieron la importancia de la hemoglobina A1c (Hb A1c) como un predictor de consecuencias en pacientes con diabetes mellitus. En 1994, la Asociación Americana de Diabetes comenzó a recomendar metas específicas para Hb A1c, pero la falta de comparación entre los ensayos limitó la capacidad de los médicos para usar estos objetivos. El Programa de Estandarización Nacional de Hemoglobina Glicosilada (NGSP) fue implementado en 1996 para estandarizar los resultados de la Hb A1c según los estudios DCCT / UKPDS. El NGSP certifica a los fabricantes de métodos de Hb A1c como trazables al DCCT. Los criterios de certificación se han reforzado con el tiempo y el NGSP ha trabajado con el Colegio Americano de Patólogos en establecer requisitos estrictos para la aptitud de los ensayos. Como resultado, la variabilidad de los valores de la Hb A1c entre los laboratorios clínicos se ha reducido considerablemente. La Federación Internacional de Química Clínica (IFCC) ha desarrollado un sistema de referencia para la Hb A1c , que facilita la trazabilidad de la metrología a un orden superior. El NGSP mantiene la trazabilidad a la red de la IFCC a través de continuas comparaciones de muestras. Ha habido controversias en relación a si el informe de los resultados de Hb A1c debe ser en unidades IFCC o NGSP, o una estimación promedio de glucosa. Los diferentes países se encuentran tomando esta decisión. La variabilidad entre los resultados de Hb A1c se ha reducido considerablemente. No todos los países informarán Hb A1c en las mismas unidades, pero se han establecido ecuaciones que permiten la conversión entre diferentes unidades. Ahora se recomienda Hb A1c para el diagnóstico de la diabetes, acentuando aún más la necesidad de un ensayo de óptimo rendimiento. El NGSP proseguirá sus esfuerzos para mejorar los tests de Hb A1c asegurando que se cumplan las necesidades clínicas.

BACKGROUND: The Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS) established the importance of hemoglobin A1c (Hb A1c) as a predictor of outcome in patients with diabetes mellitus. In 1994, the American Diabetes Association began recommending specific Hb A1c targets, but lack of comparability among assays limited the ability of clinicians to use these targets. The National Glycohemoglobin Standardization Program(NGSP) was implemented in 1996 to standardize Hb A1c results to those of the DCCT/UKPDS. CONTENT: The NGSP certifies manufacturers of Hb A1c methods as traceable to the DCCT. The certification criteria have been tightened over time and the NGSP has worked with the College of American Pathologists in tightening proficiency-testing requirements. As a result, variability of Hb A1c results among clinical laboratories has been considerably reduced. The IFCC has developed a reference system for Hb A1c that facilitates metrological traceability to a higher order. The NGSP maintains traceability to the IFCC network via ongoing sample comparisons. There has been controversy over whether to report Hb A1c results in IFCC or NGSP units, or as estimated average glucose. Individual countries are making this decision. SUMMARY: Variability among Hb A1c results has been greatly reduced. Not all countries will report Hb A1c in the same units, but there are established equations that enable conversion between different units. Hb A1c is now recommended for diagnosing diabetes, further accentuating the need for optimal assay performance. The NGSPwill continue efforts to improve Hb A1c testing to ensure that clinical needs are met.

Hemoglobina glicosilada A1c como criterio diagnóstico de diabetes y pre-diabetes / Glycosylated hemoglobin as a diagnostic criterion for diabetes and pre diabetes

The clinical usefulness of A1c glycosylated hemoglobin (A1c), in the metabolic control of diabetic patients is well known and the goal is to achieve values below 7 percent to prevent the appearance of microangiopathic complications. Standardized measurement methods are required to obtain trustful values. The proposal of the American Diabetes Association to accept A1c as a diagnostic criterion for diabetes and as a means to identify subjects at risk of developing the disease is currently being discussed. The establishment of universal cutoff points has been hindered by the fact that factors such as ethnic influence on glycosylation may modify values of A1c. The use of A1c as an alternative to blood glucose measured during fasting ad after a 75 g glucose load, will not be possible without standardizing measurement methods and performing studies to validate it as a diagnostic method in different populations, including Chileans.

Hemoglobin A1c: past, present and future

Hemoglobin A[HbA] has been used for decades to monitor the control of glycemia in diabetes. Although HbA1c is currently undergoing a reassessment, and major developments have been underway in recent years, HbA1c is not recommended at present for diabetes screening or diagnosis. The objective of this review is to summarize the recent developments and to review a potential diagnostic role for HbA1c. Implementation of changes in HbA1c results and units of measurements have been suggested for the purpose of test standardization. These include lower reference ranges [by about 1.5-2 points] and measurement units expressed in percentage [%], as mg/dL [mmol/L] or mmol/mol [or a combination of these units]. In diabetes screening and diagnosis, the current diagnostic guidelines use measurement of plasma glucose either fasting or after glucose load. These diagnostic methods have shortcomings warranting a potential diagnostic role for HbA1c. While recent developments in HbA1c methodologies are acknowledged, it is not yet known which changes will be implemented, and how soon. Given the recent literature supporting HbA1c diagnostic abilities, and given the shortcomings of the current guidelines, it is possible that a diagnostic role for HbA1c may be considered in future practice guidelines, globally. Very recently, the first of such recommendations has been proposed by an expert panel, as announced by the US Endocrine Society

A importância da determinação da hemoglobina glicada no monitoramento das complicações crônicas do diabetes mellitus / The importance of glycated hemoglobin determination in the management of chronic complications associated with diabetes mellitus

O diabetes é uma situação clínica muito freqüente que envolve cerca de 7 por cento da população mundial. Por essa razão muitos esforços têm sido empregados na implementação de métodos de monitoramento e no desenvolvimento de terapias efetivas para o seu controle. A hemoglobina glicada (HbA1c) é o teste mais indicado na quantificação do risco de complicações crônicas em pacientes diabéticos. O Diabetes Control and Complications Trial (DCCT) e o United Kingdom Prospective Diabetes Study (UKPDS) concluíram que o risco de complicações em pacientes diabéticos é diretamente proporcional ao controle glicêmico, determinado através dos níveis de HbA1c. A medida exata e precisa da HbA1c é uma questão importante para os laboratórios clínicos, sendo que vários fatores podem afetar as determinações, levando a resultados equivocados. O objetivo deste estudo é demonstrar os diferentes métodos para a quantificação da HbA1c, bem como discutir os problemas mais freqüentes de padronização dessa determinação.

Diabetes is a widespread disease, involving about 7 percent of the entire world population. For this reason, many efforts have been devoted to the wide application of valid monitoring procedures and to the development of effective therapeutic approaches. Glycated hemoglobin (HbA1c) is the pre-eminent factor for quantifying the risk of chronic complications in patients with diabetes. The Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS), demonstrated conclusively that risks for complications in patients with diabetes are directly related to glycemic control, as measured by glycated hemoglobin (HbA1c). Accurate determination of HbA1c is an important issue for clinical laboratories and several factors may affect and lead to erroneous results. The main objective of this study is to show the different methods for glycated hemoglobin quantification and to discuss the most frequent problems of standardization glycated hemoglobin measurements.

Estudio de confiabilidad interexamen de la hemoglobina glicosilada para el diagnostico de la Diabetes Mellitus / Inter examination reliability study of the glycosylated hemoglobin in the diagnosis of Diabetes Mellitus

Pregunta de investigación: ¿cuál es la confiabilidad interexamen de la hemoglobina glucosilada para diagnosticar en forma precoz a los pacientes portadores de diabetes mellitus?. Objetivos: 1.- Determinar la variabilidad interexamen entre dos ó mas pruebas de hemoglobina glicosilada en un mismo sujeto. 2.- Conocer si algunas variables pueden alterar la prueba de hemoglobina glucosilada en un mismo sueto. Diseño: Estudio de confiabilidad interexamen. Ambiente: Hospital Obrero No 1 de la CNS, servicio de Medicina Interna y pacientes diabéticos internados y atendidos en consulta externa. Pacientes: casos consecutivos. Métodos: Pacientes con y sin diabetes fueron estudiados en tres ooportunidades distintas, usando el mismo método de hemoglobina glicosilada. Entre el grupo de pacientes diabéticos se estudiaron personas con todos los nieles de severidad de la enfermedad. En cada paciente se estudiaron una serie de covariables. Los datos se estudiaron con análisis de correlación, estadísticas de asociación y coeficiente de correlación intraclase. Resultados: El coeficiente de correlación intraclase muestra resultados substanciales a casi perfecto. No se encontraron covariables que influyan en la estabilidad del examen. Conclusiones: La hemoglobina glicosilada se mantiene estable en mediciones repetidas. Este hecho refuerza la utilidad de su uso en el diagnóstico y manejo de la diabetes.(au)