 In 1999 researchers determined that ELISA-based saliva testing “can serve as a reliable [method] for estriol determination.” A 2007 article reported that the free testosterone measurement, including via saliva assay, represents “the most sensitive biochemical marker supporting the diagnosis of PCOS.” In 1990 Vuorento, et al., found that luteal phase defects, wherein progesterone levels decline prematurely within the menstrual cycle, were identified with high frequency using salivary progesterone testing among women suffering from unexplained fertility.In 2009 Shibayama, et al., examined the accuracy of salivary androgen measurement for diagnosing late-onset hypogonadism (age-related decline in androgens, often called "andropause").Researchers determined that the accuracy of saliva testosterone and DHEA measurement exceeded 98.5% and that this method "has satisfactory applicability" in the diagnosis of late-onset hypogonadism.