How accurate are fructosamine tests?

We recently had taken my cat to the vet to discuss some of the possibilities as to why she had some small seizures. The vet does think it is diabetes related...but is not completely positive. Recently my cat has been only needing 1 insulin shot per day b/c either her amps or pmps is too low (in the 130-170's). Her curves have been good as well- often in the 80's, and on one day it was 68 which did make me a little nervous. The vet thought maybe she was becoming a transient diabetic and asked to conduct a fructosamine test. Now, while she was at the vet she was extremely nervous, as she always is, which always makes her blood sugar increase, she was also in the car for 40 minutes. I got the results today and they said her average blood sugar was 402...which is strange b/c she was no where close to that number over the past five days.
So, does anyone have any thoughts in regards to this? Even the vet tech thought it was weird but said that it was an average of her blood sugar from the past five days???
Thanks!
Dianne

 

This articles says that the fructosamine is for 1-2 weeks http://www.vet.uga.edu/vpp/clerk/bates/index.php

 

The number for the fruitosimine test are not directly comparable to that of BGs. Here is the conversion from: Based on normal=250-400
Fructosamine Average BG
250 120
300 150
325 180
350 210
400 240
450 270
475 300
500 330
Based on normal=200-350
Fructosamine Average BG
200 90
250 120
288 150
325 180
363 210
400 240
438 270
475 300
513 330

http://www.sugarcats.com/infirmary/fructosamine.asp

 

That's interesting that the numbers do not match, which makes me feel better if her average was not 402 but rather 240. Why didn't the vet tech know that or at least tell me that? Thanks so much for the information everyone!
Dianne