Intercycle variability of ovarian reserve tests: results of a prospective randomized study

Background: This study was designed to assess prospectively the intercycle variability (ICV) of basal FSH (bFSH), clomiphene citrate challenge test (CCCT) (analysis of the CCCT was performed by the parameter: SigmabFSH + sFSH) and exogenous FSH ovarian reserve test (EFORT) (analysis of the EFORT included the following parameters: estradiol (E-2) increment and inhibin B increment 24 h after administration of FSH), and secondarily to assess the influence of the variability of these ovarian reserve tests. Methods: Eighty-five regularly menstruating patients, aged 18-39 years, participated in this prospective study, randomized, by a computer-designed four-blocks system into two groups. Forty-three patients underwent a CCCT, and 42 patients underwent an EFORT. Each test was performed 1-4 times in subsequent cycles, one test per cycle. During the first three cycles, patients were treated with intrauterine insemination (IUI). Follicle number and oocyte yield during IVF ovarian stimulation in the fourth cycle were taken as measures for ovarian reserve. Results: The per cycle variance of bFSH ranged from 1.8 to 4.4 (maximum to minimum ratio of 2.44, P<0.0001), while that of CCCT ranged from 21.3 to 70.6 (3.31, P<0.0001). No significant change in per cycle variance was found for the E-2 increment (1.25, P>0.2) and inhibin B increment (1.31, P>0.2), which were the EFORT parameters. A large ICV of CCCT and bFSH test results was strongly associated with lower ovarian reserve. Conclusions: Our study shows that the ICV of the inhibin B increment and the E-2 increment in the EFORT is stable in consecutive cycles, which indicates that this reproducible test is a more reliable tool for determination of ovarian reserve than bFSH and CCCT. Women with limited ovarian reserve show a strong ICV of bFSH and FSH response to clomiphene citrate.