Home ovulation test. Packet and contents of a 'Boots own brand' home ovulation test kit. The test works by detecting a surge in luteinizing hormone that marks the onset of ovulation. The absorbent end of the dipper (lower right) is dipped in a urine sample. Two blue lines appear in the windows on the side of the dipper. If the surge line is darker than the reference line the woman has begun to ovulate. Ovulation is the release of an egg from an ovary. Because the egg only survives for 24 hours, detecting the start of ovulation aids planning for a pregnancy. Luteinizing hormone is secreted by the anterior pituitary gland, stimulating ovulation.