1.Colorimetric method
1)using nitrobluetetrazolium (NBT) Serum is added to carbonate buffer containing NBT(pH 10.8, 37 ˚C)The assay is based on the reducing properties of fructosamine under alkaline conditions. Fructosamine reduces NBT and the change in absorbance is measured at 530 nm.
Interfering substances
1) EDTA and heparin plasma samples give lower fructosamine results than serum
samples in the NBT colorimetric assay.
2) Urate and glutathione produce artificially high results in the NBT assay.
3) Vitamin C >227 μmol/L interfere significantly with the NBT colorimetric assay.
4) Cysteine, methyldopa, dobesilate calcium and oxytetracycline can cause artificially
low fructosamine results (all assays).
5) Bilirubin >34.2 μmol/L has been shown to cause falsely elevated fructosamine results
(all assays).
6) Haemolysis can also cause falsely low results (all assays).