Efecto de las condiciones de conservación de la muestra de orina en el análisis de catecolaminas por HPLC

Autores

Dayana Álvarez-Mejías, Pamela Loaiza-Yee

RESUMEN

A nivel de la Caja Costarricense del Seguro Social, la medición de catecolaminas únicamente se realiza en el Laboratorio Clínico del Hospital San Juan de Dios, por lo que se considera de suma importancia determinar el efecto de las diferentes condiciones de almacenamiento de la muestra sobre la estabilidad de las catecolaminas urinarias, así como verificar la precisión y veracidad de la metodología utilizada. Se utilizaron alícuotas de un pool de orina humana, las cuales se almacenaron bajo diferentes condiciones de pH, temperatura y exposición a la luz. Las concentraciones de catecolaminas obtenidas se compararon contra una alícuota con las condiciones de almacenamiento recomendadas por el fabricante. La técnica utilizada fue cromatografía líquida de alta resolución acoplada a un detector electroquímico. La verificación de precisión y exactitud se realizó de acuerdo con la guía EP15 A2. Se encontraron diferencias estadísticamente significativas en las condiciones de alteración de pH y el sometimiento de la muestra a tres ciclos de descongelado para la noradrenalina y dopamina; el almacenamiento de la muestra en refrigeración afecta los niveles de dopamina medidos. Niveles de pH entre 5.5 y 6.0 no conducen a oxidación de las catecolaminas en la muestra de orina. Los ciclos de descongelamiento provocan pérdida en la recuperación de las catecolaminas. Periodos cortos de exposición de las muestras de orina a la luz no provocan pérdida de estabilidad de las catecolaminas. Aunque existen diferencias estadísticamente significativas, las diferencias porcentuales entre las concentraciones determinadas no se consideran clínicamente significativas, pues no generan una interpretación diagnóstica distinta.

Palabras clave

catecolaminas, noradrenalina, adrenalina, dopamina, cromatografía líquida de alta resolución, detector electroquímico HPLC.

ABSTRACT

In the Caja Costarricense de Seguro Social, the measurement of catecholamine is only carried out in the Clinical Laboratory of Hospital San Juan de Dios, so it´s considered very important to determine the effect of the different storage conditions of the sample on the stability of urinary catecholamine, as well as verify the accuracy and veracity of the methodology used. Aliquots were used from a pool of human urine, which were stored under different conditions of pH, temperature and exposure to light, the concentrations of catecholamine obtained were compared against an aliquot with the storage conditions recommended by the manufacturer. The technique used was high performance liquid chromatography coupled to an electrochemical detector. The accuracy and accuracy verification were carried out in accordance with the EP15 A2 guide. Statistically significant differences were found in the conditions of alteration of pH and the subjection of the sample to three thawing cycles for noradrenaline and dopamine; storage of the sample in refrigeration affects the measured dopamine levels. At pH levels between 5.5 and 6.0 there is no oxidation of catecholamine in the urine sample. Thawing cycles cause loss in the recovery of catecholamine. Short periods of exposing urine samples to light do not cause loss of stability of the catecholamine. Although there are statistically significant differences, the percentage differences between the determined concentrations are not considered clinically significant, since they do not generate a different diagnostic interpretation.

Keywords

catecholamine, noradrenaline, adrenaline, dopamine, high performance liquid chromatography, electrochemical detector, HPLC.
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