The testing principle of ovulation test strips is mainly to determine whether ovulation occurs by detecting the change in the level of luteinizing hormone (LH) in urine. The details are as follows:

Hormonal Changes during the Female Ovulation Cycle

During a woman’s menstrual cycle, hormonal levels change cyclically. Before ovulation, the follicles gradually develop and mature. The hypothalamus secretes gonadotropin – releasing hormone, which stimulates the pituitary gland to secrete follicle – stimulating hormone (FSH) and luteinizing hormone (LH). As the follicles develop, the levels of FSH and LH gradually increase. Around 24 – 48 hours before ovulation, there is a significant peak in LH, known as the LH surge. The LH surge is a key factor leading to ovulation. It causes the mature follicle to rupture and release the egg.

Detection Mechanism of Ovulation Test Strips

Ovulation test strips use the principle of immunochromatographic double – antibody sandwich method. The test strip contains monoclonal antibodies against LH, which can specifically bind to LH in the urine. When LH in the urine binds to the antibodies on the test strip, an antigen – antibody complex is formed. Then, the complex moves along the test strip and binds to another marker (such as colloidal gold or enzyme, etc.) on the strip, forming a visible color band.

Principle of Result Display

• Negative Result
  When the LH level in the urine is low, not enough LH binds to the antibody to form a significant complex, or the amount of the formed complex is insufficient to make the test line show color. At this time, the color of the test area (T) is lighter than that of the control area (C), presenting a negative result, indicating that ovulation has not occurred yet.
• Positive Result
  When the LH in the urine reaches its peak value, a large amount of LH binds to the antibody, forming a sufficient amount of complexes, making the color of the test area (T) the same as or darker than that of the control area (C), presenting a positive result, suggesting that ovulation will occur within 24 – 48 hours.