The change in T/C ratio indicates the increase or decrease of LH levels in the tested urine. (Test line as dark as the control line = 1. Test line lighter than control = less than 1. Test line darker than control = greater than 1.)
T/C ratio has positive correlation with LH level so its change can reflect the LH level change. Therefore T/C ratio is used to measure the increase or decrease of LH level in urine.