[Pre-diabolic]

Is it possible for the OGTT to give a false positive result?

My 2 hour OGTT reading was 11 (198) a few days ago. The doc put me on Metformin 500mg x 2. A1C result is 5.2% and cholestrol is normal. My daily meter readings are also fine - 4.3 (77) before breakfast and 5.5-6.5 (99-117) throughout the day. I'm 31 and 155 lbs.

My doc can't explain the readings. I'm going to see an Endo to rule out diabete 1.5.

Any ideas?

[lorilei]

Are you watching to see how much your Bg rises between pre-meal and two hour post and not limiting your carbs...that might give us an idea how your body deals with actual foods..kind of like a daily scope of what you are eating and your readings would help...out of curiosity, why the OGTT? any other symptoms beforehand?

[Pre-diabolic]

I reguested the OGTT. Two fasting tests prior came out normal. My father has Type 2. I have been getting reactive hypo symptoms for about 3 years on and off. Lately, they were more frequent and pronounced. Started to also get hyper symptoms last few weeks - tired, fuzzy, can't concentrate, pressure in eyes.

Below are test results for last 4 days plus diet. This morning my fasting levels was actually 3.6 (65).

Before/after breakfast 4.1/5.9 (74/106) - Allbran, banana, milk, protein shake
Before/after lunch 5.1/5.3 (92/95) - Sandwich with 2 slices of whole grain bread, milk
Before/after dinner 5.2/6.4 (94/115) - healthy dinner with protein, good carbs, veggies
Night 5.1 (92)
Healthy snacks in between such as almonds, cheese, fruit

[Ronin]

Hi Pre-Diabolic!

A false positive OGTT? I cannot say because I'm not an MD, but clearly your body did not use up the glucose in the alloted time. Could this be a sign of Type-1.5? Yes, it can, but your HbA1c says that you should be making sufficient insulin to cover your needs. Then again 75 grams of Glucose at one shot is, or at least shouldn't be, "normal."

The key test, and I'm surprised that they didn't do it along with the OGTT, is your C-Peptide level. That indicates how much insulin your body produces. Too low and you are either LADA or Type-1.5 and you would need an antibody test to see if your immune system is attacking your pancreas.

Important note: if you are either LADA or Type-1.5 Metaforim will only give you side effects as it is a drug designed to overcome insulin resistance, and if you aren't making sufficient insulin in the first place that drug will not help.

Finally, the readings you show in your last post would seem to indicate that either the Metaforim is working, or that you don't actually have a problem.

FWIW: In your initial post, you cite your age and weight. Weight relates to height for purposes of determining if you might be insulin resistant (IR) age doesn't count.

[REDLAN]

Is it possible for the OGTT to give a false positive result?

OGTT is considered the gold standard test for diabetes. So if you check out the sensitivity and specificity you get them listed as 100%, a perfect test. A year or so a go Wiki listed Sensitivity and specificity for OGTT and it was lower, particularly the specificity. (specificity is the one that relates to false positives)

regardless of the status of OGTT as a gold standard, it is possible to generate false positives with OGTT.

1) Giving too much glucose for body weight. If you weigh close to 45Kg, then a standard adult dose may be too much

2) Illness - known to affect BG levels, and also OGTT. Febrile illness can most certainly affect the body's ability to remove glucose from the blood stream, as could an injury, recent surgery, and sudden and unexpected stress.

3) low carb eating - bit disputed this one, but eating significantly less than 150g per day can cause a false positive. Apparently it's due to low circulating insulin levels and a reduction in glucose uptake. (similar problem happens to OGTT in gestating women apparently)

4) the menses can affect OGTT

5) ethnicity can cause false positives according to WHO - different populations have quite different OGTT profiles, and so choosing a cutoff designed for white people of European descent can then mean that those with a normal OGTT for their race get diagnosed incorrectly.