Journal Article

Dialysis with icodextrin interferes with measurement of serum <i>α</i>‐amylase activity

Gerrit Schoenicke, Bernd Grabensee and Joerg Plum

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 17, issue 11, pages 1988-1992
Published in print November 2002 | ISSN: 0931-0509
Published online November 2002 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/17.11.1988
Dialysis with icodextrin interferes with measurement of serum α‐amylase activity

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Background. The glucose polymer icodextrin has gained a widespread use in peritoneal dialysis especially in patients with low ultrafiltration and high peritoneal transport properties. In patients using a once‐daily exchange with icodextrin, a decreased serum amylase activity has been reported. We explored the potential underlying mechanisms of this effect.

Methods. Using standard chromolytic methods, serum amylase activity was measured in blood samples from 11 patients on icodextrin treatment and from 11 patients on conventional glucose treatment. Samples were additionally supplemented with α‐amylase and unused icodextrin dialysis fluid. Potential complex formation between icodextrin and α‐amylase was studied by SDS‐gel electrophoresis with protein silver staining and fluorophore‐assisted carbohydrate staining with the AMAC (FACE) method, which provides oligosaccharide labelling. Lipase activity was measured in parallel in all samples by two standard methods.

Results. Amylase activity was reduced by 90% in serum from patients using icodextrin for the long dwell (15.9±10.9 U/l) vs patients using standard glucose (157.1±23.7 U/l; P<0.001). Addition of icodextrin to serum samples from patients using conventional glucose solutions induced a dose‐dependent decrease in amylase activity. The assay results indicated a substrate competition between ET7‐G7PNP and icodextrin. AMAC fluorophore staining of icodextrin and subsequent gel electrophoresis failed to demonstrate complex formation between icodextrin and α‐amylase. Unlike the amylase findings, icodextrin did not affect lipase activity.

Conclusions. The present findings indicate that icodextrin competitively interacts as a substrate in the amylase assay. In support of this, fluorophore‐assisted oligosaccharide electrophoresis on SDS gel failed to reveal the formation of an ‘amylase/icodextrin complex’. Lipase measurement should provide an alternative and unconfounded method for diagnosing pancreatitis in icodextrin patients.

Keywords: α‐amylase activity; icodextrin; interaction; lipase activity; pancreatitis; peritoneal dialysis

Journal Article.  2715 words.  Illustrated.

Subjects: Nephrology

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