Comparison of the GnRH-stimulation test and a semiquantitative quick test for LH to diagnose presence of ovaries in the female domestic cat

It is generally recommended that female cats not intended for planned breeding are spayed to reduce the population of feral cats and also because spaying is beneficial for the long-term health of the individual. For female cats of unknown origin or with estrous symptoms after spaying there is a need for a reliable method to diagnose or rule out the presence of ovaries to avoid unnecessary surgery. Methods previously recommended include vaginal cytology, evaluation of serum estradiol concentration during suspected estrus, induction of ovulation and subsequent evaluation of progesterone, or explorative laparotomy. These methods have the disadvantages that an accurate diagnosis only can be made during estrus or that an invasive procedure is required. Previously, the use of a GnRH challenge test and a semiquantitative LH test have been reported. Our aim was to compare these two methods. We therefore divided 31 female cats in two groups: (1) intact nonestrous females (N = 16), and (2) previously ovariohysterectomized females (N = 15). A blood sample was collected (Time 0) and 0.4 μg/kg buserelin (Receptal; Intervet, Danderyd, Sweden) was injected im. A new blood sample was collected 120 min after the injection. A drop of serum from the sample collected at Time 0 was placed on the LH test (Witness LH; Synbiotics, Corp., San Diego, CA, USA) and the result was evaluated as negative or positive. The remaining serum was frozen and analyzed for estradiol in one batch. Serum estradiol before buserelin stimulation ranged between 5 and 45 pmol/L (N = 14) in intact nonestrous queens and between 2 and 6 pmol/L (N = 15) in ovariohysterectomized females. Estradiol in samples collected after 120 min ranged between 12 and 51 pmol/L (N = 16) in intact queens and between 1 and 7 pmol/L (N = 15) in spayed cats giving a sensitivity and specificity of 100% for the buserelin stimulation test at a cutoff value of 11 pmol/L. All intact queens were negative in the semiquantitative LH test while 14/15 spayed cats were positive and one was negative giving a sensitivity of 100% and a specificity of 93.8% to detect the presence of ovaries in nonestrous cats.