Hi bb
I found this on the web:

"How does Vitex or Chaste berry work?
Vitex or Chaste tree berry acts on the hypothalamus and pituitary glands by increasing luteinizing hormone (LH) production and mildly inhibiting the release of follicle stimulating hormone (FSH). This results in a shift in the ratio of estrogen to progesterone, with a rise in progesterone. The ability of chaste tree berry to raise progesterone levels in the body is an indirect effect, so the herb itself is not a hormone."

My interpretation is that yes Vitex could raise the levels of LH in your body - but not sure if that means a false positive or just early ovulation?

Sorry if this is not helpful.