# Variant Hook Effect - false negative by hCG beta core fragments



## sandflower

Hello Everyone,

I looked up false negative hcg tests and found info on the variant hook effect that some might find interesting. I'm not sure about link posting rules, so you can search it on google.

In the women who are affected by it (it's harmless to the baby), tests done later in pregnancy can be lighter than tests done earlier, or an actual false negative occurs. It is much more common than the hook effect some people talk about, where hcg levels are so high they ruin the test. The cure is the same: dilute the test urine and retest it. 

The variant hook effect works like this: At, or after, 5 weeks of pregnancy there can potentially be enough hcg that has broken down into incomplete parts in the urine that there is an abundance of hcg beta core fragments. These are a particular formation of the broken down hcg, and are only found in the urine. If someone for some reason has too many hcg beta core fragments they will saturate one of the antibodies used for hcg tests and are unable to bind to the other antibodies on the test, leaving a false negative.


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## sandflower

I'm not saying it's ever happened to me, just wanting to share the info. 

Of course, if anyone has experience with diluting for the test please share.


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## dreamer1978

Interesting! Thanks for posting. Hasn't happened to me, but I've read about it. :hugs:


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## MillieJoan

I'm actually hoping that's what happened to me the other day! I had some leftover internet cheapies, and because I've lost my symptoms over the past week, I was a little worried, so I took a test Saturday morning to reassure me.... Well, the test line was only about half as dark as the control, whereas my tests weeks earlier (I'm 8+4 today). I freaked out!! Then of course I started frantically googling, and read about the variant hook effect. I have my first ultrasound on Thursday, so I'm praying with all my might that's what happened, and that there's a nice, strong heartbeat...


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## sandflower

MillieJoan said:


> Well, the test line was only about half as dark as the control, whereas my tests weeks earlier (I'm 8+4 today). I freaked out!!

That's why they say not to keep testing. From what I've heard, symptoms can come and go without any problems. Also, test sticks can vary on their own in how dark they get, even within the same brand. 

If you want you could try diluting, but if it doesn't get darker it would probably be due to the added water. Let us know if you try it.

Good luck on the ultrasound on Thursday! Will you be getting picturs to post?


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## MillieJoan

I'm not sure, but really hoping so! I decided not to take any more, even diluting the samples--I don't want to worry myself any more before that scan. Thanks for the well-wishes, and I'll update once I know more! :flower:


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## babyhearts

When I was pg with my son 3 and a half years ago i tokk a test a week for 10 weeks and had blood and urine tests at the drs all showed neg until 10 weeks weird ay xx


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## sandflower

That's odd to have to wait 10 weeks. Maybe some people's hcg breaks down when it first enters their system, or just doesn't go from it's source to the blood for some reason.

Were you ever given an explanation, or had other unusual symptoms with it? I can imagine doctors not being too cooperative about checking for pregnancy after the first test.


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## babyhearts

sandflower said:


> That's odd to have to wait 10 weeks. Maybe some people's hcg breaks down when it first enters their system, or just doesn't go from it's source to the blood for some reason.
> 
> Were you ever given an explanation, or had other unusual symptoms with it? I can imagine doctors not being too cooperative about checking for pregnancy after the first test.


I did test myself till I would have been about 5/6 weeks I had extream headaches I was so tired I took holiday and slept for the whole time I couldn't eat or think lol pretty normal things,
My doctor who is also a long time family friend was convinced it was pregnancy and was a little annoyed it came up neg so I was sent away to bring in a first morning sample again neg I then spent a week at home doing tests nothing then was sent for a blood test still nothing then when I went to get the results another wee test then I popped a few more in until I gave one last go and it came up positive 
He never really said much except it isnt unheard of some people go months without knowing I have had problems with PCOS since a young age and that came up but never got a 100% 
This time it showed 1 day after my missed period so who knows it was all very strange!


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## sandflower

So, I decided to try the concept with an opk. 

The first came up negative with a very faint line, since I'm not ovulating today. Urine gets diluted with distilled water, and the second opk comes up negative with a slightly darker line. Urine gets diluted again and the third comes up with a noticeably darker line than the 2nd attempt. Then my roommate starts banging on the door since we share a bathroom, so it all ends with three. 

Is my bottle of water ovulating, or is there something with dipping multiple opks?

p.s. I now understand why people complain about and make apologies for their stick pictures.
 



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## sandflower

With the OPKs, it wasn't the water--water only test, from the same bottle of water, came up fully negative. It's too bad, I was looking forward to the look on the return-counter person's face.

Maybe dipping the opk test in contaminates the sample for future OPK tests?


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## ashleygregory

I took 3 pregnancy tests like the one in the picture, before I went to the clinc. All three said negative, and then when I went to find out why I was throwing up all the time, and missed my period, the test there came back positive. Then they did a blood test to confirm. I just have no luck with those store bought tests for some reason.


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## Sunflower2318

I heard about this, and did experiment with some leftover HPTs when I was 7 weeks. The first IC came up really faint, much lighter than I had been testing when I first found out I was pregnant. That freaked me out a bit, so I diluted the same urine by a ratio of about 1 part to 10 parts water and tested again with two more ICs. They came up really dark immediately. I repeated the same experiment the next day, and the same thing happened. It's so weird to see; I wouldn't have believed it unless I saw it for myself.


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## Fermerswife

I know I'm resurrecting a really old thread but I was looking for info on this as my 5+3/4 weeks tests were starting to get ever so slightly lighter and I thought this might help anyone in a similar position.

The bottom test in this pic I diluted my urine by about 50%.
 



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## jyhinds

Hi Millie,

I know this is an old post but I just wanted to see how your pregnancy went because I am in the same boat now. I am about 7w4d and my test was much lighter today and I am freaking out. That was the last hpt I had and I dont have another to try the dilute test. I had an u/s on friday which showed a 7wk baby with hb 135. So, i don't know why I took another test today, but now I am very worried. I hope everything turned out well for you!


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## Bumpblessing4

I've known two women who continually got false negative urine pregnancy tests. One finally took a blood test that was positive when a urine test was negative yet again (and she had plenty of HCG that the urine test should have detected). The other one was an ultrasound tech, and because her urine tests were repeatedly negative but she still felt pregnant, she did an informal ultrasound on herself at work and saw a 9 week baby right away. Crazy, huh? I've heard that some women test darker in the afternoon than they do with first morning urine (which is more concentrated) so that would also go along with the hook theory.


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## Strawberry123

Hi everyone,

Also bumping this old thread because I found it so useful. Have never posted anything on forums like these before, but decided to share my experience in case it helps others.

I'm currently 7+5 weeks on my 3rd pregnancy. DD1 born June 2010 and a mc in sept 2012 at around the same stage I am now. Because of what happened last time, I'm a bit paranoid and bought a big bag of HPTs to keep testing with. I know you're not supposed to keep testing, but despite bleeding at 7 weeks I didn't have an ultrasound or bloods done till week 10 (loooong story...), by which time my bHCG was so low I wouldn't have got a positive on a urine test. Basically I think I lost the baby really early on, then the bleeding at 7 weeks was my next period. Went nearly out of my mind over those 3 weeks waiting to find out if I was still pg or not, and I figured if I took regular tests this time round I could save myself some anguish should the same happen.

So here I am, testing 1x or 2x a week, and over the last week the line has been getting fainter and fainter. This morning I tested and it was so faint, if I didn't know better I'd say there was nothing there at all. So I consulted Dr Google and came across this thread. Just want to say a massive THANK YOU for saving my sanity. I tried the dilution trick, and BFP was back. Good job it's New Year's Day and the GPs are shut because I was about to go in and make a bit of a fool out of myself!

I've attached a pic of my 'experiment'- hope it works as posting this on my phone. The test on the left of the image is the one from this morning. Guess this was the most concentrated pee, as I said at the time I thought it was negative, though by the time I did the other tests there is a very small line. The tests to the right were done after reading this thread. I dipped the sticks in pee with concentrations 100%, 50% and 10%. The last test was a control, dipped in water only (marked 0%). Pretty clear, huh!

The thing I can't believe is this means there's only a ~3 week ish window in which tests like these are accurate and don't give false negatives? Ok for those actively TTC and obsessively weeing on sticks (guilty!), but what about those women who just think they are late, possibly in denial about the situation therefore waiting to test? I feel like there should be more info with the test packaging, stating if you're already at least 3-4 weeks late and still BFN then try
diluting the pee?

Anyway, thanks again!! 

Edit: aaaargh, photo upload probs- file is too large. Will try and figure out how to resize on phone, otherwise will do in another post underneath on PC tomorrow!


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## Strawberry123

Ok, think I've figured it out, though it appears to be rotated, so test on the left is now test on the bottom!
 



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## Gensom

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## elena626

bumping this old thread since it has calmed me down:)
currently 5 1/2 weeks and did test with fmu. It was about half as dark as the test control line. Drank lots of water and the next test was about as dark as the control line.
Had no idea that this effect could already be measured this early:s


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## Katiemayurbex

Strawberry123 said:


> Ok, think I've figured it out, though it appears to be rotated, so test on the left is now test on the bottom!

Thank you so much for this! I'm 7 weeks and 1 day and my tests were going crazy. Feeling so reassured xxx


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## Mumof12

This thread is brilliant as although I did a thread on the hook effect yrs ago with pics on here I was around 8 weeks well because I had some tests left I too peed on one yesterday and noticed the line getting lighter still dark but noticeably lighter than previous tests that was on a 3 hr sample so predictable again about 45 mins later and bam line dark again so today did one of my last 2 tests and line was half the strength of a few days prior so diluited 50/50 and dark line again now I knew all about the hook effect as mentioned previously but didn't realize it could start this early as I'm around 5+2 so this thread has really helped me also got my 3 + on a digital on the 45 min hold pee so it really can start early x


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## Classic Girl

So can the hook effect do the same to cbd with weeks or just the sticks?


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## Mumof12

It seemed to have an effect on the digital for me too x


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## Classic Girl

Mumof12 said:


> It seemed to have an effect on the digital for me too x

Thank you for this! I took a cbd with weeks a few times during week 4 and midway thru week 5. All 2-3 :growlmad: I had a scan at 5+3 showing gest. sac and (dr saw) a yolk sac ( i've stared at many ultrasound pictures on the Internet and did not see the clear yolk sac but he saw it forming). At 6+1 I started spotting which wasn't super heavy, no clots, no cramping and went in at 6+2 for another scan showing a much larger gest. sac and clearly defined, gorgeous yolk sac...no reason for bleeding and no real amount of blood coming from anywhere. Spotting/bleeding subsided (never even halfway filled a panty liner and anything that made it to the liner was brown) so I started to feel more hopeful. At 6+5 took another cbd to see.........1-2! :cry: I flipped out, honestly. I have another scan Thursday (at 7+3) and desperately praying to see a heartbeat. Limbo sucks


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## Moom7900

Classic Girl said:


> Mumof12 said:
> 
> 
> It seemed to have an effect on the digital for me too x
> 
> Thank you for this! I took a cbd with weeks a few times during week 4 and midway thru week 5. All 2-3 :growlmad: I had a scan at 5+3 showing gest. sac and (dr saw) a yolk sac ( i've stared at many ultrasound pictures on the Internet and did not see the clear yolk sac but he saw it forming). At 6+1 I started spotting which wasn't super heavy, no clots, no cramping and went in at 6+2 for another scan showing a much larger gest. sac and clearly defined, gorgeous yolk sac...no reason for bleeding and no real amount of blood coming from anywhere. Spotting/bleeding subsided (never even halfway filled a panty liner and anything that made it to the liner was brown) so I started to feel more hopeful. At 6+5 took another cbd to see.........1-2! :cry: I flipped out, honestly. I have another scan Thursday (at 7+3) and desperately praying to see a heartbeat. Limbo sucksClick to expand...

Good luck for your scan tomorrow! Xxxx


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## Classic Girl

Thank you. I'm strangely positive and at peace. But trying to prepare myself for what could be.


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