# Fructosamine

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Fructosamine is a compound that can be considered the result of a reaction between fructose and ammonia or an amine (with a molecule of water being released). A fructosamine is also formed when carbonyl group of glucose reacts with an amino group of a protein, as the double bond to oxygen moves from the end carbon atom to the next carbon atom and water is released. Fructosamines formed from serum proteins such as albumin are known as glycated serum protein (GSP), and are used to identify the plasma glucose concentration over time and so assess diabetic control over an intermediate period of time.1

## Indications

Glucose control is usually assessed in diabetes with the Glycosylated hemoglobin (HbA1c) measurement that indicates average glucose levels over the preceding 12 weeks, as reflected by the permanent glycosylation of a small fraction of the haemoglobin molecules in the person's blood. However, this is not appropriate where there has been a recent change in diet or treatment within 2-6 weeks, or if there are abnormalities of red blood cell aging or mix of hemoglobin subtypes (predominantly HbA in normal adults). Hence, people with recent blood loss or hemolytic anemia, or hemoglobinopathy such as sickle-cell disease, are not suitable for some glycosylated hemoglobin methods that do not account for higher-turnover hemoglobin. Fructosamine is used in these circumstances, as it also reflects an average of blood glucose levels, but over a shorter period of 2 to 3 weeks. Fructosamine is also of use in conditions, such as pregnancy, in which hormonal changes cause greater short-term fluctuation in glucose concentrations.

## Interpretation of results

There is no standard reference range available for this test. The reference values depends upon the factors of patient age, gender, sample population, and test method. Hence, each laboratory reports will include the patient's specific reference range for the test. An increase in fructosamine in lab testing results usually means an increase in glucose in the blood.

On average, each change of 3.3 mmol (60 mg/dl) in average blood sugar levels will give rise to changes of 2% HbA1c and 75 µmol fructosamine values.2 However, this overemphasizes the upper-limit of many laboratories' reference ranges of 285 umol/L as equivalent to HbA1c 7.5% rather than 6.5%. A comparative study,3 which has been used in official advice for Quality and Outcomes Framework guidance in the UK4 and summaried by the United States' National Quality Measures Clearinghouse:5 gives the following formula and resulting values:

${\rm HbA1c} = {\rm 0.017} \times {\rm Fructosamine} + {\rm 1.61}$
Hence:
${\rm Fructosamine} = ({\rm HbA1c} - 1.61) \times {\rm 58.82}$
Fructosamine
(µmol)
HbA1c
%
HbA1c IFCC
(mmol/mol)
200 5 31
258 6 42
288 6.5 48
317 7 53
346 7.5 58
375 8 64
435 9 75
494 10 86
552 11 97
611 12 108

## Footnotes

1. ^ Delpierre G, Collard F, Fortpied J and Van Sschaftingen E (2002). "Fructosamine 3-kinase is involved in an intracellular deglycation pathway in human erythrocytes" (PDF). Biochem. J. 365 (Pt 3): 801–8. doi:10.1042/BJ20020325. PMC 1222720. PMID 11975663.
2. ^ Bartol T (2000-12-01). "Comparison of Blood Glucose, HbA1c, and Fructosamine". Retrieved 2007-06-04. - gives a comparison chart and cites following source:
• Nathan DM, Singer DE, Hurxthal K, Goodson JD (1984). "The clinical information value of the glycosylated hemoglobin assay". N. Engl. J. Med. 310 (6): 341–6. doi:10.1056/NEJM198402093100602. PMID 6690962.
3. ^ Cohen RM, Holmes YR, Chenier TC, Joiner CH (2003). "Discordance between HbA1c and fructosamine: evidence for a glycosylation gap and its relation to diabetic nephropathy". Diabetes Care 26 (1): 163–7. doi:10.2337/diacare.26.1.163. PMID 12502674.
4. ^ "Diabetes (DM) Indicator 20 The percentage of patients with diabetes in whom the last HbA1c is 7.5 or less (or equivalent test/reference range depending on local laboratory) in the previous 15 months" (PDF). Quality and outcomes framework Guidance 2006. BMA. p. 39. Retrieved 2008-01-02.
5. ^ "Diabetes mellitus: the percentage of patients with diabetes in whom the last HbA1c is 7.5 or less (or equivalent test/reference range depending on local laboratory) in the previous 15 months". National Quality Measures Clearinghouse. 2007-12-31. Retrieved 2008-01-02.