¿Funciona la medicina basada en la evidencia?

LONDRES – La medicina basada en la evidencia, como escribieron David Sackett y sus colegas en 1996, es “la aplicación explícita, minuciosa y prudente de la mejor evidencia disponible a la toma de decisiones para la atención de cada paciente”. Definición que a primera vista parece inobjetable; de hecho, muchos dirán que eso es la “medicina”, a secas. Pero la idea se ha vuelto objeto de un arduo debate, y muchos piensan que ya no sirve. El mes pasado, el British Medical Journal preguntó a sus lectores si la medicina basada en la evidencia dejó de funcionar, y las respuestas fueron prácticamente parejas: 51% por el sí y 49% por el no.

La controversia es sobre el tipo de evidencia. Sackett da a entender, pero no estipula, que las decisiones de los médicos deberían basarse en la evidencia epidemiológica (resultados de ensayos aleatorizados controlados y de estudios de muchos años de duración con grandes cohortes) y, previsiblemente, en la opinión del paciente.

Los estudios epidemiológicos intentan responder preguntas como “si 1000 personas con diabetes tipo 2 se dividen aleatoriamente en cuatro grupos de 250 personas a las que durante diez años se les darán, respectivamente, los fármacos A, B, C o ninguno (o un placebo), ¿qué sucederá con las tasas de supervivencia y qué complicaciones y efectos secundarios puede haber?”. Si el ensayo se realiza correctamente (con una cantidad suficiente de sujetos divididos en forma realmente aleatoria y valorando los hallazgos “a ciegas”), los resultados deberían ser confiables.

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