Fructosamine

Both fructosamine and HbA1c tests are used primarily as monitoring tools to help people with diabetes control their blood sugar. HbA1c is most frequently used being a very reliable marker. Fructosamine may be useful in situations where HbA1c cannot be reliably measured however measurement is not standardised meaning no reference intervals can be recommended and one laboratory’s results can be compared to another. Fructosamine is also not free from problems being affected by conditions that affect circulating proteins. However the conditions fructosamine measurement may be useful include:

• RBC loss or abnormalities – the HbA1c test will not be accurate when a patient has a condition that affects the average age of red blood cells (RBCs) present, such as haemolytic anaemia or blood loss. The presence of some haemoglobin variants may affect certain methods for measuring HbA1c. In these cases, fructosamine can be used to monitor glucose control.
• Rapid changes in diabetes treatment – fructosamine allows the effectiveness of diet or medication adjustments to be evaluated after a couple of weeks rather than months. This is rarely undertaken however with capillary (finger prick) glucose testing being the most widely used alternative to monitor day to day control.
• Diabetes in pregnancy – good diabetes control is essential during pregnancy, and the needs of the mother frequently change during gestation; fructosamine measurements may occasionally be requested along with glucose levels to help monitor and accommodate shifting glucose and insulin requirements. This is rarely undertaken however with capillary (finger prick) glucose testing being the gold standard.

The fructosamine test is not used to diagnose diabetes. The World Health Organisation recommends a glucose or HbA1c blood test if diabetes is suspected.

Although not widely used, the fructosamine test may be of value in the above situations.

If a patient’s fructosamine is increased, then the patient’s average glucose over the last 2 to 3 weeks may have been elevated. In general, the higher the fructosamine concentration the higher the average blood glucose level. Trends may be more important than absolute values primarily due to lack of assay standardisation and wide variety of values between people (intraindividual and interindividual biological variation) reference intervals are difficult to validate. If there is a trend from a normal to high fructosamine, it may indicate that a patient’s glucose control is not adequate – that they are getting too much sugar or their treatment has become less effective. In these situations, diet and treatment plans may need to be reviewed.

Fructosamine results must be evaluated in the context of the patient’s other clinical findings. Falsely low fructosamine results may be seen with decreased blood total protein and/or albumin levels, with conditions associated with increased protein loss, or with changes in the type of protein produced by the body. In this case, a discrepancy between the results obtained from daily glucose monitoring and fructosamine testing may be noticed. Also, someone whose glucose concentrations swing erratically from high to low may have normal or near normal fructosamine and HbA1c levels but still have a condition that requires frequent monitoring.

High levels of vitamin C (ascorbic acid), lipaemia and haemolysis can interfere with test results.

No. HbA1c is used most of the time to monitor (and diagnose) diabetes. It is the best single test for establishing an estimate of longer term control. Fructosamine is rarely required and only sometimes performed in the situations described in this article.