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For those of you worrying about false negative pregnancies (and I am one of those with the missing menstruations, having 3 kids before this and testing positive for all 3, I have been there done that, been there, done that, been there, done that, LOL and I know I am PG) Since I have a MS in biochemistry and I kind of sort of understand this stuff, I decided to see if there was any medical proof to make us ladies breathe a sigh of relief and rea__sure us that we are not insane (at least about this) and guess what, after about 10 minutes of searching…I found medical proof that testing negative while being pregnant happens. I will try my hardest to make this as simple as possible because these guys talk in code sometimes…ugh!!!!!
Article: D. Yunus, H. Muppala, F. Hamer & F. Clarke : Three Consecutive False Negative Pregnancy Tests in a Twin Pregnancy: A Case Report . The Internet Journal of Gynecology and Obstetrics. 2007 Volume 6 Number 2:
Case: A 27-year-old lady, in her third pregnancy;
Symptoms: missing her period for 10 weeks, vomiting constantly, losing weight. When admitted to the ER, she appeared to be severely dehydrated and slightly jaundice. An abdominal exam indicated nothing out of the ordinary.
Test: Urine a___lysis which showed ketones +++, blood ++, glucose + and pregnancy test was negative.
(FYI-Ketones are a highly acidic substance, lots of them in the urine usually means the person is headed to Diabetes land-which looks like a really fun salt free time, ugh! These ketones can make you very sick and since they are so acidic, will skew any results of urine a___lysis because they are so reactive)
Oh the Irony: performed 2 more urine tests, both negative. However, someone seemed to have their thinking caps on and decided to perform an ultrasound and guess what…she was 9 weeks + 5 days with twins. Well, they stabilized her, rehydrated her, never found any reason for the jaundice other than she was freaking pregnant!!!! She went on to deliver healthy twins at 38 weeks gestation.
Now for the science part…what could have caused the false negative, not once, but three times? The study indicated the following 6 possibilities… (These are NOT my findings, only my interpretations of those findings & I am NOT a doctor, just a nerd)
1. Science has proven there are multiple forms of hCG in maternal plasma or urine. Why so many? Well, think of it like a car factory, if you walked into the place, you would see different stages of cars being built, some would have tires on, some would be all done and shiny, and some would be just a frame. They will all be cars at some point in time, after all the parts are added onto them. Well the same thing is happening in Uterus Land- hCG is being a__sembled and it is in various stages of being built. Because the forms are shaped differently and certain parts are exposed on some while hidden on others, they will perform differently (like the car without doors would not have good wind resistance) or not react at all (Like the frame with no engine or tires). For this specific case, the doctors think that because this lady had 2 sacs & 2 placentas, that basically there was freaking chaos down there producing so many different types of hCG from 2 different sources, that the test was unable to accurately pinpoint any of it- basically overloading it. Or perhaps the one type of nCG the test looks for was hidden behind all the other types.
2. Another theory was that since she was jaundiced, obviously her liver and kidneys were not functioning as they should, so she had a high rate of bilirubin- which is a substance produced in bile, gives people the “yellow” color. Bilirubin also has a nasty habit of quickly binding to any colored dyes, and hello, what does the urine a___lysis use but colored dyes! So if this bonded to the dye first, there was no way the hCG even had a chance to get in there and participate, so to speak ;)
3. Dehydration leads to concentrated and less urine production which in turn might contain high concentration of hCG. Which means the test should have quickly become positive, right? Actually no, these tests have a maximum limit, if it is reached, the test does not work. If concentrated urine is suspected, the urine samples should be diluted to 1 in 10 or 100. Maybe we could all try this one at home, just make sure you use bottled water.
4. Since dehydration leads to concentrated and acidic urine having a pH below 5 (you could grab a pool test kit and see for yourself if this pertains to you), then the test might not be able to do its job. These kits are designed to test urine pH 5-9 with hCG concentrations at 20 mIU/mL. However, if your urine has a pH below 5 (0-4), it causes the hCG to stay bonded with the water in the urine and not react or ignore the test. For this lady, she had those nasty, ketones (which are like those bullies in school who would always cut in line) and they definitely would make the hCG more soluble in urine or stay bonded with the water). However, you could have exceptionally high acidic urine & that may be why those false negatives are occurring.
5. The kidneys only clear 30% of the hcg, the rest is cleared by liver & kidneys in conjunction. If there are problems with the liver, as with this lady, all of the hCG may be clearing in the kidney leading to really high levels of hCG and this thing called the high dose hook effect. Prof. Larry Cole (see the end to find out who this guy is) states that most tests will present a hook effect problem at hCG levels ]200000 mIU/mL in urine. Okay… basically there is so much hCG and science knows they are in the various stages of being built that the test can’t find the one it is suppose to bind with…it is just too crowded. Plus the upper limit for the best test available is 600000 and it only recognizes one type of hCG. So in other words, it would be like sticking your finger into alphabet soup and trying to finding just the Z’s without touching anything else and getting distracted… Could someone with normal liver functions produce an abnormally high hCG levels during pregnancy, why not? Stranger things have happened!
6. The last theory is having Defective or misshapen ?-hCG and/ or rapid clearance of the hormone from the circulation. There is a very rare, but also way under-diagnosed disorder called trophoblastic disease which produces ordinary and irregular forms of human chorionic gonadotropin (nicked hCG, hCG missing the beta-subunit C-terminal segment, hyperglycosylated hCG, and free beta subunit); all of which would not react with the urine test. FYI- trophoblastic diseases are tumors that develop from placental cells, most are harmless and never get very big, some are cancerous, some are large, and some believe this is what causes molar pregnancies and miscarriages, but studies are inconclusive. For the most part, it is not really something you worry about, nor would you ever be diagnosed with, because we get our cervix cells check and that is annoying enough, could you imagine having someone sc___p your placenta??? So, unless you are having major fertility issues or other female issues, this would go unnoticed in most women.
Something interesting about this study as well…According to Prof. Larry Cole, the Friedman and Howard Distinguished Professor of Ob-Gynae, who is an authority on ?-hCG and runs a HCG Reference Service at the University of Mexico, USA; the 99% accuracy quoted by manufacturer means that it detected at least 99% of high (]100mIU/mL) hCG standards. It has zero relationship to what percent of pregnancies it detects (meaning, it does NOT have a 99% accuracy amongst the people who use it to test for pregnancy, only that if there is normal hCG ]100IU/mL, then it is 99% accurate in finding those correctly shaped hormones). Interesting to know….
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