Do OPK sticks work as pregnancy tests?

[AnnieLobeseder]

I seem have vague memories that they work the same way?

I've been so tired lately, and literally conked out on the sofa this afternoon, and vaguely thought to myself that I only conk out like that when I'm pg, a thought that woke me up with a jolt, I can tell you! I have an old OPK stick from ttc DD2, and it came up with a very dark line straight away. I'm hoping the simple answer is that, by conincidence, I'm ovulating. But I've got a Mirena, which I think it supposed to suppress ovulation. I don't have periods anyway - they never came back after DD2 was born a year ago.

So, do I need to rush out to the supermarket for a proper test?

No they do not work the same way; luteinising hormone (LH) is detected by an OPK. There are two main problems with usage of OPK's; first these assume that there is only one rise in LH every month and that such a rise is followed by ovulation. Both of these are simply not true.

The OPK you used may be beyond its use by date.

The Mirena will suppress periods as well as ovulation.

Thanks for the info, but why was the test +ve then?

Off for a proper test now anyway...

Actually hcg does interfere with opks. I am not sure in what quantities but after my last miscarriage I was using opks while waiting for my hcg level to go back to zero and I was getting really dark lines for the first couple of weeks. I was 9/10 weeks so the hcg levels would have been very high. The opk stopped showing a line before the pregnancy test did, so it is not very sensitive.

However, I think that is theoretical and probably not relevant to you. As Attila says the opk is probably out of date, so try not to worry.

I'd get a test anyway to be sure.

With DS2 I did an ov test and it came up positive on the day I also did a positive pg test!

LH is similar on a molecular level to HCG (which is why HCG is used to trigger ovulation in an IVF cycle). For this reason, an OPK may show positive when there is a pregnancy. See here for more info (under the heading 'OPK as HPT').

However, the more likely explanation is, as Atilla says, that you've used an out-of-date stick. Although Mirena does suppress ovulation it is not infallible, so if you think you may be ovulating I guess you might want to use condoms as well (and get your coil checked).

Actally, I think I got the windows the wrong way around!

Got a test from the supermarket, which was -ve (phew!), and if the OPK windows are the same way around, then the OPK was -ve too.

Panic over... but made me think it's time to nag DH about that vasectomy again!

HCG and LH do cross react, so an OPK might likely show positive if you have HCG around. This certainly happened to me when I was looking to see when I started ovulating after my scond miscarriage - the tests showed positive for a week or so, but it was actually becasue I still had high enough HCG levels to give a positive pregnancy test.

It doesn't work the other way round though, ie you can't use a pregnancy test to detect LH, becauause the levels are much lower.

It is not at all an accurate use of these tests though so if you want to know if you are pregnant, just use a pregnancy test, not an LH one.