How to Avoid a False Positive on Glucose Test?

[Laurucha]

I am 25 weeks pregnant and am supposed to go in for my one-hour glucose test in a couple days. This is the screening test that determines whether you need to go in for the three-hour glucose test that determines whether you will be considered to have gestational diabetes. I have read that around 25% of women test positive at the one-hour test, and only 15% of these women end up having gestational diabetes according to the results of three-hour glucose tolerance test. I really want to avoid being one of these many false positives. I have a phobia of needles and am not sure I could handle getting four blood draws in one morning.

Does anyone have any ideas as to how to minimize my chances of getting a false positive? My doctor said that I can eat up to two hours prior to the test. He said that fasting would probably increase my chances of testing positive. It's going to be hard to eat two hours prior to the test, because the test is first thing in the morning and I would be sound asleep at that time. I also have a hard time getting food down early in the morning. If I get up extra early and manage to eat something, would it be best to eat something high in protein or are some carbs okay?

I believe I have a tendency to be hypoglycemic, though I have never had any testing done. I feel unwell if I go long without food. When eat foods high in sugar or drink a soda, I get sleepy and sometimes a little light-headed, especially on an empty stomach. It was years before someone told me that I needed to have high-protein snacks to keep my energy level up. Anyway, I am guessing that this means that I will likely have pretty low blood sugar an hour after ingesting the glucose drink, but I can't be sure.

Your advice is appreciated!

[dangerbunnygirl]

I also feel icky if I don't eat frequently enough or have to much sugar.

I did my glucose test in the morning and my midwife suggested having a good, high protein breakfast, it meant I had to get up really early but my test went fine and I felt good. I brought a snack for after. I think I ate (eggs and toast) half an hour before I drank the icky Glucola stuff, and make sure you are hydrated because you aren't supposed to eat or drink after taking it.

Good luck.

[Youngfrankenstein]

I believe that having a good before bed snack can help morning blood sugars anyway.  I wouldn't worry about the false positive.  You can always re-take the 1 hour.  You could also offer to monitor your own sugar for 3 days or so.

[fruitfulmomma]

I would eat a high protein meal and stear clear of the carbs until after they are done. 

[Laurucha]

Thanks to everyone for the input. I will try to choke down an egg early tomorrow morning. Youngfrankenstein, I'm going to be switching doctors soon, so I don't know my new OB, but I know the HMO well, and they like to follow protocols. I can always make a stink and refuse the three-hour test, but I don't know if my OB will be receptive to other testing options. I'll just keep my fingers crossed that I pass!

[Worldshakerz]

With my first pregnancy I drank the nasty orange drink and they said I was "borderline" gestational diabetes. I don't handle processed/high  carb foods well and they put me on a "diabetic diet" which was way to high in carbs for me. It makes no sense ( I stuck with a more sensible for me lower carb diet and my son was perfectly healthy and so was I). My second pregnancy I insisted I do a different test which I got to eat a balanced breakfast and then get my blood drawn. I passed that one with flying colors. 

[Plummeting]

I guess it's too late now, but if anyone else sees this, if you are able to take the test later in the day, you are less likely to fail. Insulin resistance is highest in the morning, which means glucose tolerance is lowest in the morning. It's not a way to cheat the test or anything (and I personally would want to know if I had GD - I do think it's kind of a big deal) but it is a good way to prevent getting a false positive by just a few points. Both times I've used OBs they just told me to stop eating 2 hours ahead of time - I wasn't required to test in the morning or anything. :)

[katt]

probably too late, but i just decline to test.

I would test if there were other signs that indicate I would need to, but if everything is going normally, why should i?

[Plummeting]

Originally Posted by katt 

probably too late, but i just decline to test.

I would test if there were other signs that indicate I would need to, but if everything is going normally, why should i?

Because you could still have GD, and GD usually doesn't present with symptoms, but can cause fetal hypoxia if not managed, which can lead to all sorts of other problems. It's not just about having big babies. Polycythemia as a result of uncontrolled blood sugar is not a laughing matter, and will make your baby feel pretty darn crappy, even though they'll probably be just fine (but then again, maybe they'll need all kinds of interventions in order to get to that "just fine" state). I declined the test in favor of monitoring myself at home. I had no symptoms at all, and I still don't, but I definitely have GD. This idea that you're going to have overt symptoms is not true for everyone.Because I generally eat a very healthy diet, I wouldn't expect to be spilling tons of sugar in my urine, and I never have at my appointments, because most of the time my blood sugar is totally fine just following my normal diet. However, I've found there are certain things I simply cannot eat - totally healthy things, like homemade bean soup! - because they send my blood sugar through the roof. Those highs are what cause periods of hypoxia for the fetus, and would likely never be detected through urine testing in the office.

[Laurucha]

I read some informative discussions in the archives about glucose testing and why some people choose to forgo the tests. There are some very legitimate criticisms of how gestational diabetes is diagnosed. Personally, if I was going to refuse the tests, I would put myself on a diabetic diet just in case. A diabetic diet is a healthy diet for anyone, but I would rather not be concerned when I occasionally indulge in something sweet or high in refined carbs.
 

Originally Posted by Plummeting 

I guess it's too late now, but if anyone else sees this, if you are able to take the test later in the day, you are less likely to fail. Insulin resistance is highest in the morning, which means glucose tolerance is lowest in the morning. It's not a way to cheat the test or anything (and I personally would want to know if I had GD - I do think it's kind of a big deal) but it is a good way to prevent getting a false positive by just a few points. Both times I've used OBs they just told me to stop eating 2 hours ahead of time - I wasn't required to test in the morning or anything. :)

Good to know! I was actually wondering about that this morning while waiting for my test. I always feel kind of crappy in the morning in a way that makes me think it is related to low blood sugar. I am waiting for my results now, but if I get a borderline result I think I will try a do-over of the one-hour test instead of going straight to the three-hour test.

[Plummeting]

Originally Posted by Laurucha 

I read some informative discussions in the archives about glucose testing and why some people choose to forgo the tests. There are some very legitimate criticisms of how gestational diabetes is diagnosed.

Honestly, I think those criticisms are based on outdated/false information. I've seen it stated multiple times at MDC that blood sugar is normally higher in pregnant women, when in fact, the opposite is true; because of increased blood volume, normal blood sugar in pregnant women is LOWER, even in the third trimester, after the placenta starts putting out all those hormones that increase insulin resistance. People used to think that the cutoffs on the tests were too low, but based on what is truly normal for pregnant women, they simply aren't. Also, a lot of people seem to think that if you normally eat a very healthy diet, then suddenly get a big glucose load, it's going to give you a false positive. That also isn't true. If everything is functioning as it should, your pancreas should be able to crank out the required amount of insulin and your muscles should respond appropriately to that insulin, so that your blood sugar will not rise to unusually high levels. The only time this isn't the case is when a woman has been following a restricted carb diet (not just a normal, healthy diet), and that's because your body has been accustomed to burning fat instead of glucose. That's why they require the 3 days of unrestricted carb intake before the 3 hour test - to be sure that, if you were eating a very low carb diet, your body is back to burning glucose instead of fat. And if a woman is following this sort of diet, then the simple solution to not getting a false positive, caused by the diet, on the one hour screen, is to just eat 150-200 healthy carbs a day for 3 days before the test. :)

I'm not saying that I think there's anything wrong with not testing. I don't. I just think that, if a woman doesn't even know why she would bother, she might need more information. There are some very good reasons to know if you have GD, even in the absence of symptoms. I'm positive I wouldn't be having symptoms right now, even if I didn't know. I have had to make only minimal alterations to my diet, excluding things like that bean soup I mentioned, lol. Otherwise, my bg is always normal, except for occasional higher numbers in the morning, but I've been able to manage those easily, and they aren't high enough to cause me to spill sugar in my urine, and I definitely don't think they're high enough to cause macrosomia. I guess this means that my case probably isn't serious and maybe everything would be fine, even if I did nothing, but I can't know that for certain, and I'd rather be safe than sorry. 

Edited by Plummeting - 4/13/12 at 1:33am

[holly6737]

Don't eat any carbs before the test. Only eat protein- eggs, bacon, cheese, etc. The 1 hour test is only a screening test. It's the 3 hour test that's diagnostic. Good luck!

[phathui5]

While it can be important to know what your blood sugar is doing, there are options for testing that don't involve drinking the sugary stuff. You can do a random glucose with a finger stick or blood draw, an A1C, the one hour glucose with real food instead of the drink...

 

Originally Posted by Plummeting 

Because you could still have GD, and GD usually doesn't present with symptoms, but can cause fetal hypoxia if not managed, which can lead to all sorts of other problems. It's not just about having big babies. Polycythemia as a result of uncontrolled blood sugar is not a laughing matter, and will make your baby feel pretty darn crappy, even though they'll probably be just fine (but then again, maybe they'll need all kinds of interventions in order to get to that "just fine" state). I declined the test in favor of monitoring myself at home. I had no symptoms at all, and I still don't, but I definitely have GD. This idea that you're going to have overt symptoms is not true for everyone.Because I generally eat a very healthy diet, I wouldn't expect to be spilling tons of sugar in my urine, and I never have at my appointments, because most of the time my blood sugar is totally fine just following my normal diet. However, I've found there are certain things I simply cannot eat - totally healthy things, like homemade bean soup! - because they send my blood sugar through the roof. Those highs are what cause periods of hypoxia for the fetus, and would likely never be detected through urine testing in the office.

[Isabel57]

I did my glucose test in the morning and my midwife suggested having a good, high protein breakfast, it meant I had to get up really early but my test went fine and I felt good.

[Plummeting]

Originally Posted by phathui5 

While it can be important to know what your blood sugar is doing, there are options for testing that don't involve drinking the sugary stuff. You can do a random glucose with a finger stick or blood draw, an A1C, the one hour glucose with real food instead of the drink...

 

Her question wasn't why she should do this particular test. Her question was why she should test AT ALL. I was telling her why she might want to know if she had GD, not why she might want to do the glucose screening test. If you read my posts about GD, I declined the one hour test, and moved straight to home monitoring. I do have GD. I'm aware of all the other options, although I personally think the A1C is a bad idea, because if you don't develop carbohydrate intolerance until after 28 weeks, the A1C isn't going to help you much. It's a test that shows your average blood glucose over the past three months. If you test at 28 weeks, then your A1C should be normal. If you test at 32 weeks, it might still be normal, even if you've had a month of slightly elevated blood sugar. Also, a random glucose is not going to be helpful if you just so happen to do it when your BG is low or normal. I have experienced a couple readings over 150 (which is way too high), but I also sometimes have readings under 60 (which is very low). I can eat some things and have a bg of 87 an hour later. A one time random draw or stick is just not an accurate way to dx GD. You might luck out and draw it when it's high, but you might not. Then you'd walk around thinking things were great, all while having several readings a week that were way outside the normal range.

I also wanted to edit to say that the A1C is not accurate if you have anemia caused by iron deficiency - that will cause it to be falsely elevated. Additionally, since A1C doesn't actually measure average blood sugar, but rather glycation (which is related to blood sugar, but not in the direct, absolute way people seem to think it is), some people are going to be more susceptible to falsely low, high, or normal A1Cs. It's just not a good test for diagnosing anything, and especially not for diagnosing GD before it causes problems. I would hate for an anemic woman to rely on it, get an elevated A1C, and think she's got GD, when she absolutely doesn't.

Edited by Plummeting - 4/27/12 at 6:05pm

[dovemama]

Thanks for pointing out another option phatui5....

I am pretty sure that is one way of avoiding a false positive