Diagnostic test properties of serum progesterone in the evaluation of luteal phase defects.

The existence of LPD has been controversial, mainly because of inconsistencies in its diagnosis. The endometrial biopsy remains as a gold standard until newer and better tests are developed. Additional information may be provided from serum P determinations in the luteal phase by using the likelihood ratios and positive predictive values obtained in this study. Since the properties of sensitivity and specificity are inversely related, the selection of discriminatory cutoff level of serum P would optimize one at the expense of the other. There is no value that combines both sensitivity and specificity as far as correlation with endometrial biopsy is concerned.