The ovulation test detects the peak of the LH hormone released by the pituitary gland leading to the release of the egg from the ovary 24-48 hours later.
To perform the ovulation test properly, you should start testing several days before the expected date of ovulation, about three days before. For example, if the woman has her period every 28 days and theoretically ovulates on day 14, start testing on day 11-12 of the cycle. The first urine of the morning should not be used and the test should be repeated twice a day about 12 hours apart. In addition, the patient must be consistent and do the test daily until it is positive.
The test uses test strips and/or digital devices, which have different sensitivities, measured in international measurement of units per litre (IU/L). The minimum amount of LH that the test can detect in the urine is about 10 to 40 IU/L. Thus, tests with high sensitivity (10 IU/L) are more likely to detect a peak of LH even though it is lower, than those with low sensitivity (40 IU/L).
A negative ovulation test can also be due to the following reasons:
- The woman has done the test with the first urine of the morning, or without following the instructions correctly.
- The patient has tested too far in advance of the LH peak (e.g. patient with long cycles).
- The LH peak can be short (2 hours) and when the patient tested, it was too late for the test to be positive. It is therefore advisable to do it twice a day.
- The sensitivity of the test used is low and does not detect the specific LH peak of the patient.
It is also worth noting the possible false positive results: the test may be positive but there is no ovulation:
- The peak LH produced from the pituitary gland may be high but not followed by ovulation at ovarian level.
- In women with polycystic or multifollicular ovaries there is a peak of LH but no consequent ovulation.
Conclusion: Ovulation tests are not exact tests and should be carried out carefully in the knowledge that they can lead to false negative and/or positive results.
