Advantages of new glucose 'watches'?

QHow do the new 'wristwatch-style' glucose monitoring systems work and what are their limitations?

AConventional intermittent capillary blood glucose monitoring devices provide only a snapshot and thus not the true fluctuations of blood glucose levels. Also some patients are reluctant to monitor themselves as often as they should because of the inconvenience, pain and expense.

The latest non-invasive self-testing devices that may be worn wristwatch-style use a 'continuous glucose monitoring system'. They take readings automatically up to three times an hour by monitoring the patient's interstitial fluid, which directly reflects blood glucose concentration. The fluid is extracted from under the skin via a small disposable pad and measured electrochemically, and the results are displayed on the watch-like monitor.

Drawbacks are that glucose levels in interstitial fluid may lag five to15 minutes behind those of capillary blood. Also a finger-prick is still required for calibration every 12 hours.

Concern has also been expressed that the device is better at detecting higher glucose levels than lower ones and that excessive wrist movement or strenuous exercise can invalidate results.

The devices are expensive, costing around £350 each plus £50 for a box of 16 disposable pads.

Mr Barry Hill is

the chief biomedical scientist

at Wigan Royal Infirmary