prelude4ws
New member
Before reading, it might be helpful to see these previous posts by /@mcg1102:
With an uptick in folks using apps like Premom and Femometer to determine OPK positivity, I thought this might be a good overview of what those LH ratio numbers mean and how to analyze them. These apps use a photograph of a standard LH strip and compare the darkness of the test line compared with the control line as a quantitative ratio of test darkness divided by control darkness. These strips usually include directions that state that the OPK is considered “positive” when the test line is as dark or darker than the control – therefore, a positive OPK is one in which the app algorithm determines a ratio of 1.00 or higher.
Often, these apps also determine some ranges of low, medium, high, and peak. These are sometimes defined by certain ratio ranges; “peak” may be defined as anything above 1.00 or the highest ratio that you have logged that cycle. These ratios differ from those of the Clearblue Advanced Digital, which uses “high” fertility reading to note a rise in estrogen and “peak” to indicate when LH has surged.
The biggest misconception I see is plugging in the app-determined low/high/peak on FertilityFriend when one is using standard OPKs. To understand why that’s not accurate, 1) we have to know how LH strips work in relation to hormone levels in the urine and 2) we also have to know the differences between surges and peaks and their relation to ovulation.
LH strips and pregnancy tests (and yes, rapid COVID tests, too) work the same way, called in the field “sandwich assays” or lateral flow tests. Essentially, in the test line, there are antibodies that recognize LH; the dye that moves over the test has another set of antibodies that also recognize LH but have a dye linked on them. If LH is present, it gets sandwiched between the test line antibodies and the dye-linked antibodies, which creates a line that you can see. The control line has antibodies that just recognize the other antibodies – so there should always be a line, unless the test is faulty.
Why is there almost always a test line?
Because we almost always have LH being expressed! There’s variation in baseline levels, but generally they stay under 15-ish IU/L. See below for the general ranges of LH concentrations at different points in the cycle (source):
Your LH strip will have a test line equal to or darker than the control line at some point during your LH surge (more to come on what that means later). Different brands have different sensitivities, but most LH strips will be “positive” if your urine LH concentration is above 20 IU/L. See the list of common brands and their sensitivities for positive results below:
A ratio of under 1 just means that you don’t have enough LH in your urine to hit your strip’s sensitivity; for most strips, that’s pretty indicative that your actual surge hasn’t started yet. You can ignore the “high” readings, and just use them to see if you should be testing more frequently. If you rarely catch a positive OPK, it could be that you need a higher sensitivity brand. If you get a positive on one brand and not another, it could be because they have different sensitivities.
TL;DR Part 1: You can almost always ignore “medium” or “high” readings – they’re still negative, although they can tell you if your surge is starting to get stronger. We’re looking for the “peak” – or a standard OPK with a ratio of 1 or higher. Reframe your thinking to negative & positive instead.
In standard charting courses, we’re taught a more textbook approach: LH should peak one day before ovulation, and temp rise should follow the next day. It turns out there’s tons of variations in LH surge patterns and BBT patterns that make this less of a science than you’d expect.
Let’s define some terms:
The best way to pinpoint ovulation in studies is through ultrasound, when you can see dominant follicles before ovulation and the resulting corpus luteum after ovulation. Several studies have looked at LH patterns and their relation to ovulation. Here’s a quick review of a couple:
TL;DR Part 2: Ovulation is often shortly following the first positive OPK; in many cases, ovulation has already occurred by the time you get to “peak” LH levels.
My BBT rise wasn’t until 3 days after my first positive OPK – when did I ovulate?
Unfortunately, LH testing and BBT can’t always pinpoint ovulation the way we want it to be able to – there is variability on both sides. If you have a sustained temp shift, you can note that you *did* ovulate somewhere in that window. I always assume the latest possible ovulation day for testing purposes, but the earliest possible ovulation day for possibly expecting period onset.
I had a positive OPK on CD14 and a peak OPK on CD15 – when did I ovulate?
Again, we can’t really pinpoint much based on that information alone. However, most of the time, ovulation follows shortly after the first positive OPK, regardless of when you get an OPK with the darkest test line.
I had positive OPKs for 4 days in a row – when did I ovulate?
Sounds like you have a long surge! That’s all right and is within the normal variation of LH surges. However, same thing applies, that ovulation is still more dependent on the initial rise of LH than the peak or length of the surge.
I had a positive OPK on CD14, a negative on CD15, and then a blazing positive on CD16. What gives?
Biphasic LH surges are one of the natural variations. In most cases, the first surge is still the one that triggers ovulation; this might not be the case for folks with PCOS or long/irregular cycles.
References:
(1) http://www.sciencedirect.com/science/article/pii/S0015028212021358
(2) https://obgyn.onlinelibrary.wiley.com/doi/full/10.1111/j.1471-0528.2001.00194.x
(3) https://www.fertstert.org/article/S0015-0282(07)00160-4/fulltext00160-4/fulltext)
Thanks for reading, and kudos if you got through all that! (Edited for formatting)
With an uptick in folks using apps like Premom and Femometer to determine OPK positivity, I thought this might be a good overview of what those LH ratio numbers mean and how to analyze them. These apps use a photograph of a standard LH strip and compare the darkness of the test line compared with the control line as a quantitative ratio of test darkness divided by control darkness. These strips usually include directions that state that the OPK is considered “positive” when the test line is as dark or darker than the control – therefore, a positive OPK is one in which the app algorithm determines a ratio of 1.00 or higher.
Often, these apps also determine some ranges of low, medium, high, and peak. These are sometimes defined by certain ratio ranges; “peak” may be defined as anything above 1.00 or the highest ratio that you have logged that cycle. These ratios differ from those of the Clearblue Advanced Digital, which uses “high” fertility reading to note a rise in estrogen and “peak” to indicate when LH has surged.
The biggest misconception I see is plugging in the app-determined low/high/peak on FertilityFriend when one is using standard OPKs. To understand why that’s not accurate, 1) we have to know how LH strips work in relation to hormone levels in the urine and 2) we also have to know the differences between surges and peaks and their relation to ovulation.
LH Strips and Sensitivities:
LH strips and pregnancy tests (and yes, rapid COVID tests, too) work the same way, called in the field “sandwich assays” or lateral flow tests. Essentially, in the test line, there are antibodies that recognize LH; the dye that moves over the test has another set of antibodies that also recognize LH but have a dye linked on them. If LH is present, it gets sandwiched between the test line antibodies and the dye-linked antibodies, which creates a line that you can see. The control line has antibodies that just recognize the other antibodies – so there should always be a line, unless the test is faulty.
Why is there almost always a test line?
Because we almost always have LH being expressed! There’s variation in baseline levels, but generally they stay under 15-ish IU/L. See below for the general ranges of LH concentrations at different points in the cycle (source):
- Follicular (pre-ovulation): 1.9-14.6 IU/L
- Midcycle (around ovulation): 12.2-118.0 IU/L
- Luteal (after ovulation): 0.7-12.9 IU/L
Your LH strip will have a test line equal to or darker than the control line at some point during your LH surge (more to come on what that means later). Different brands have different sensitivities, but most LH strips will be “positive” if your urine LH concentration is above 20 IU/L. See the list of common brands and their sensitivities for positive results below:
- Clearblue Digital Ovulation Test – 40 IU/L
- iProven – 25 IU/L
- Natalist – 20 IU/L
- One Step Standard – 30 IU/L
- One Step High Sensitivity – 20 IU/L
- Pregmate – 25 IU/L
- Premom/Easy@home – 25 IU/L
A ratio of under 1 just means that you don’t have enough LH in your urine to hit your strip’s sensitivity; for most strips, that’s pretty indicative that your actual surge hasn’t started yet. You can ignore the “high” readings, and just use them to see if you should be testing more frequently. If you rarely catch a positive OPK, it could be that you need a higher sensitivity brand. If you get a positive on one brand and not another, it could be because they have different sensitivities.
TL;DR Part 1: You can almost always ignore “medium” or “high” readings – they’re still negative, although they can tell you if your surge is starting to get stronger. We’re looking for the “peak” – or a standard OPK with a ratio of 1 or higher. Reframe your thinking to negative & positive instead.
Why the first positive matters more than the highest LH ratio number
In standard charting courses, we’re taught a more textbook approach: LH should peak one day before ovulation, and temp rise should follow the next day. It turns out there’s tons of variations in LH surge patterns and BBT patterns that make this less of a science than you’d expect.
Let’s define some terms:
- LH initial rise – the first day of LH rising above baseline levels, or the beginning of the surge
- LH surge – the total amount of time that LH is increased above baseline (follicular) levels
- LH peak – the day of the highest LH level during the LH surge
The best way to pinpoint ovulation in studies is through ultrasound, when you can see dominant follicles before ovulation and the resulting corpus luteum after ovulation. Several studies have looked at LH patterns and their relation to ovulation. Here’s a quick review of a couple:
- LH surges only end before ovulation in a small percentage (6%) of cases; 94% of cases had an LH surge continuing after ovulation (and 60% lasted more than 3 days after ovulation). This is because LH generally has a gradual decrease after ovulation, leading to an asymmetrical peak. (1)
- LH peak on average was 1.2 days AFTER ovulation, whereas the initial rise was before ovulation. (1). In another study, the LH peak came before ovulation in 68% of cases, but it came AFTER ovulation in 23% of cases (but once again, initial rise was before ovulation) (2).
- Initial Rise of LH – happened most often 1-2 days before ovulation. (Fig 4, bottom left) (2).
- The initial rise of 2.5x the baseline level of LH is necessary for ovulation (3)
- Interestingly, BBT had biggest range – in most cases 2-4 days after ovulation (so BBT can take a bit to rise after O, not great for pinpointing ovulation day) (2)
TL;DR Part 2: Ovulation is often shortly following the first positive OPK; in many cases, ovulation has already occurred by the time you get to “peak” LH levels.
FAQs:
My BBT rise wasn’t until 3 days after my first positive OPK – when did I ovulate?
Unfortunately, LH testing and BBT can’t always pinpoint ovulation the way we want it to be able to – there is variability on both sides. If you have a sustained temp shift, you can note that you *did* ovulate somewhere in that window. I always assume the latest possible ovulation day for testing purposes, but the earliest possible ovulation day for possibly expecting period onset.
I had a positive OPK on CD14 and a peak OPK on CD15 – when did I ovulate?
Again, we can’t really pinpoint much based on that information alone. However, most of the time, ovulation follows shortly after the first positive OPK, regardless of when you get an OPK with the darkest test line.
I had positive OPKs for 4 days in a row – when did I ovulate?
Sounds like you have a long surge! That’s all right and is within the normal variation of LH surges. However, same thing applies, that ovulation is still more dependent on the initial rise of LH than the peak or length of the surge.
I had a positive OPK on CD14, a negative on CD15, and then a blazing positive on CD16. What gives?
Biphasic LH surges are one of the natural variations. In most cases, the first surge is still the one that triggers ovulation; this might not be the case for folks with PCOS or long/irregular cycles.
References:
(1) http://www.sciencedirect.com/science/article/pii/S0015028212021358
(2) https://obgyn.onlinelibrary.wiley.com/doi/full/10.1111/j.1471-0528.2001.00194.x
(3) https://www.fertstert.org/article/S0015-0282(07)00160-4/fulltext00160-4/fulltext)
Thanks for reading, and kudos if you got through all that! (Edited for formatting)
