The influence of sialic acid on the ESR.

To investigate whether changes in sialic acid levels contribute to the detrimental effect of storage on the ESR, cellular and plasma sialic acid levels were measured before and after storage and compared to the ESR. Overnight storage significantly decreased the mean control group ESR, while lower post-storage ESRs were observed for the randomly-selected patient group. Neuraminidase treatment of whole blood to decrease sialic acid content significantly increased the ESR. Approximately half of stored EDTA samples showed decreased ESRs with increased plasma sialic acid, while two-thirds with artificially increased plasma sialic acid showed a decreased ESR. Overnight storage at 5 degrees C did not affect red cell sialic acid, but significantly reduced that of platelets and leucocytes, and may therefore contribute to the significantly raised plasma sialic acid levels observed after storage. Storage also significantly increased total plasma protein levels in both control and patient groups. It is concluded that sialic acid contributes to the ESR, and that plasma sialic acid levels influence the effect of storage on the ESR.