Diabetes and CKD: Pitfalls – Monitoring response to therapy

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There are two important issues to remember when assessing glucose control in patients ESRD, one relating to immediate blood sugar measurement, and another relating to longer term diabetes control.

The first has previously been mentioned on this blog. The use of icodextrin in PD solutions is increasingly common as a means of increasing fluid removal with less absorption of the solute. Icodextrin is not generally metabolized in the peritoneum but small quantities can cross into the systemic circulation where it is metabolized to maltose. Some commercial blood sugar test strips are unable to differentiate between glucose and maltose in the serum. This is not normally an issue because there is very little sugar apart from glucose in the blood. However, in patients on PD, the presence of maltose can lead to falsely elevated blood sugar readings with certain analyzers. This has lead to at least one death in a patient who was inappropriately treated with insulin in this setting. Of course, icodextrin is not the only potential source of maltose – certain IG preparations can also contain maltose resulting in similar presentations.

Traditionally, long-term monitoring of glucose control is done by regularly measuring HbA1c levels. However there are some concerns regarding the use of HbA1c in dialysis patients. RBCs in patients with ESRD tend to have shorter half-lives while the use of EPO appears to affect Hb glycation in unpredictable ways also. The relationship between HbA1c and mortality in dialysis patients is complex and contradictory results have been noted in various studies. A recently published study using data from the DOPPS study found that HbA1c was associated with mortality but only at substantially higher levels that would typically be considered normal.

One possibility is to use alternative measures of glycemic control such as glycated albumin or fructosamine. These have the advantage of not being affected by the Hb concentration. However, in contrast to HbA1c, they measure short-term glucose control only – for example, glycated albumin is a marker of glucose control over a period of about 17 days. One recent study found a significant association between glycated albumin and mortality while HbA1c was not as useful. It’s possible that the reduced association between HbA1c and glucose control in diabetics with ESRD may be a contributing factor in recurrent episodes of hypoglycemia in some patients.

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