Ovulation is the release of an egg from an ovary into the fallopian tube. Pre-ovulation, eggs develop in sacs called follicles. Throughout an ovulation cycle, these follicles undergo a variety of changes culminating in the release of an egg around 13-15 days before period onset. The timing of this release can vary significantly depending on the individual and external factors like jet lag, stress, smoking, and contraceptives. The figure below shows a visual representation of a follicle and the release of an egg.
Figure 1: Visual representation of the development of a follicle and release of an egg.
After the release of an egg, it has around 12-24 hours to be fertilized by sperm before it begins to degrade. Therefore, the time immediately after the release of the egg corresponds to the greater chance that intercourse or insemination results in a pregnancy. This time can be termed “peak fertility”.
The development of follicles is governed by various hormones in the human body. Therefore, the levels of these hormones in blood or urine can be used to predict the release of an egg from a follicle and thus peak fertility. Spikes in luteinizing hormone, estrogen (E2), and follicle-stimulating hormone (FSH) all proceed ovulation. Post ovulation, progesterone gradually increases before returning slowly to baseline around 14 days post ovulation. Therefore, LH, E2, and FSH can be used to predict ovulation while progesterone can be used to confirm ovulation. The figure below shows a rough plot of all these hormone concentrations in relation to the ovulation cycle.
Figure 2: Hormone concentrations throughout the ovulation cycle.
The Problem with "Thresholds"
Traditional urine tests like Clearblue and FirstResponse work using a "threshold". This means the manufacturer sets a threshold concentration level and when the strip comes in contact with a urine sample, it will reveal a blue line if the concentration of one of your ovulation hormones (commonly measuring Luteinizing hormone or LH for short) in the sample is above the preset concentration threshold. The problem is that for many individuals, their baseline levels of ovulation hormone are either "too low" or "too high" for the threshold technology to have an accurate response.
For example, you might be someone with an LH baseline that is naturally so low, that when your LH spikes, the manufacturer's preset threshold level is too high for the urine test to actually detect the spike. This would result in something called a "false negative" when your LH level is spiking but you're not seeing a blue line. The flip side of that is if you're someone with a naturally higher LH baseline, and every time you take an ovulation test, regardless of the time of the month, the test shows a blue line. This is called a "false positive" when your LH level is not spiking, but you are seeing a blue line. In this case, your LH levels are constantly above the threshold level that was preset by the manufacturer.
By removing the need for a threshold, and simply providing individuals with a number, you're not dealing with the possibility that your LH level is "too high" or "too low" because at DEMETER your results are relative to what your natural baseline level is.
A Scientific Discussion... If You're Into That Kinda Thing
In general, urinary LH is the most commonly used biomarker for pinpointing ovulation. There are generally two types of LH that are measured; intact and total. There is a surge in both of these LH levels around the time of ovulation.
Intact LH surges in urine around 0.35 days before ovulation +/-0.62 days. In contrast, total LH generally peaks a day after ovulation and has a much wider percentile range.
Figure 3: Urinary LH (total and intact) vs day of ovulation
Traditional urine tests measure whether or not LH is above or below a given threshold concentration by producing a coloured line if the concentration exceeds the threshold. This threshold is usually set between 20 to 100 mIU/mL. The individual's urine travels along the strip and collects various reagents as it progresses, culminating in the generation of a coloured line if LH is present in concentrations above the target threshold. Then you can conclude that your cycle is in peak fertility if the line is present.
Sometimes, the company provides a simple colourimetric reader that measures the rough intensity of the displayed line and correlates it to low fertility, moderate fertility, and high fertility. These tests give individuals greater insight into their ovulation cycle but are still based on thresholds.
A major issue with these lateral flow tests is that they do not account for the high variability in LH levels, both baseline and peak, between different individuals. As can be seen in the figure below, LH baseline values vary between 1 mIU/mL to up to 5 mIU/mL for the 10th and 90th percentile respectively. Similarly, LH peak values vary between 3 mIU/mL to 40 mIU/mL, also for the 10th and 90th percentiles. It is important to note that the peak value for the 10th percentile is below the baseline value for the 90th percentile. This is a major problem when using a threshold detection method. If the threshold is set at 3 mIU/mL, it would worth well for the 90th percentile but almost always return a false positive for anyone above the 50th percentile. Conversely, if the threshold was set at 20 mIU/mL it would always produce a false negative for anyone in the 10th percentile. In general, companies choose to set their threshold values above 20 mIU/mL, making the devices unusable for the 10th percentile. Overall, at least 1/10 individuals cannot use a standard lateral flow LH test. Note, however, that these individuals still have an LH peak relative to their baseline. This means that a quantitative test with a low enough detection limit would allow these individuals to detect their LH peak.
Figure 4: LH baseline and peak concentrations for the 90th percentile, median, and 10th percentile.
 Monitoring the menstrual cycle: Comparison of urinary and serum reproductive hormones referenced to true ovulation, Sarah Johnson 2015.
 Development of the first urinary reproductive hormone ranges referenced to independently determined ovulation day, Sarah Johnson, 2015