Perea-Carrasco et al developed an index to screen pregnant women for gestational diabetes mellitus. This can improve the current screen based on an oral glucose load. The authors are from Hospital General de Riotinto in Huelva, Spain.


Current screen used: plasma glucose 1 hour after a 50 gram oral glucose load


Parameters for new index based on testing 1 hour after a 50 gram oral glucose load:

(1) plasma glucose in mmol/L

(2) total protein in g/L

(3) fructosamine in µmol/L


index =

= (fructosamine) * (glucose) / (total protein)



• The original formula had a value of 100 in the denominator. However, when values are used in the stated units having this in the denominator does not give the correct index values.


NOTE: The fructosamine assay used is different from the "fructosamine" assay used in the USA.

• The assay referenced in the US measures glucose linked to protein. According to Tietz's Clinical Guide to Laboratory Tests and Jacobs & Demott's Laboratory Test Handbook values for a normal person can go up to 2.7 mmol/L or 2,700 µmol/L.

• The assay used in this paper appears to detect a modified fructose molecule. According to Young and Huth it is reported in mg/L and the conversion factor to µmol/L is 5.581. This gives a molecular weight of around 179.1. The molecular weight for D-fructose is 180.16. The reference range in Young and Huth is given as 202-282 µmol/L.



• The decision value for the index was 27.2.

• An oral glucose tolerance test (OGTT) is performed on women with a positive index.



< 27.2

negative; sensitivity 98%

>= 27.2

positive; specificity 88.8%

> 30.5

gestational diabetes mellitus with specificity of 96%


Performance (Table 1, page 437):

• The sensitivity is comparable to the oral glucose screening test, but the specificity and positive predictive value are superior.



• The index would be affected by variation in the fructosamine assay. The assay used in the study was a tetrazolium blue colorimetric assay read at 552 nm.


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