Keto diastix

I just tested Rhubarb's urine with keto diastix strips, and glucose was still positive, at the 28 mmol (504) colour. According to tests, if she went above 15.5 (280), shouldn't it be minimal or negative- anything but as high as it showed?

(variation from my post in L/B/L forum)

 

Glucose is going to show on ketodiastix if glucose is above that cat's 'renal threshold'. For most cats that's usually 230-250 or so. It doesn't measure HOW much higher over the threshold, it just show you glucose is spilling into the urine from the kidneys. 10 points and 200 points would look the same on a diastix.