Technical Note: Effect of Maltose interference on Glucose Test Strip Results: Interference with Octagam and Icodextrin

Background
Diabetes is the most common cause of end stage renal failure. Those patients undergoing peritoneal dialysis to treat renal failure often suffer from problems with removing fluid. This can be improved with an osmotic agent based on a polymer of glucose - icodextrin. During circulation in the body icodextrin is mainly metabolised into maltose consisting of two glucose molecules, which accumulates in the body due to a lack of the enzyme needed to break it up (maltase). This accumulation of these metabolites of icodextrin is though to give rise to serious interference problems with some glucose test strips (1, 2). In a similar manner some immunoglobulin solutions (e.g. Octagam) are administered to the patient intravenously and contain high levels of maltose. Once again, due to the lack of maltase in the circulation, the level of maltose builds up in the bloodstream.

The Problem
Some glucose test systems using a glucose dehydrogenase dependent on the co-enzyme pyrroloquinone (GDH-PQQ) show a high degree of cross reactivity with maltose. Hence patients who are hypoglycaemic have been reported to test as hyperglycaemic (2), with potentially life threatening consequences. Indeed, in the UK one fatality has already occurred, and two further adverse incidents have been reported.

The Microdot® System
The Microdot® System uses a different enzyme – a NAD dependent glucose dyehydrogenase (GHD-NAD) which shows no significant cross reactivity with maltose. Laboratory tests with maltose and Octagam have confirmed this. See attached results. Further clinical studies are ongoing. Other test strip systems that use the same type of enzyme (e.g. HemoCue), similarly, show no interference with maltose, Octagam or Icodextrin.