Our Ranges and Process
The reference ranges are calculated based on testing “healthy” folks. Estradiol, for example is based on over 1,000 measurements with patients pre-screened to be off of birth control and other hormones. We only use the data for estradiol if the progesterone is within the luteal range. The postmenopausal ranges are based on women’s samples that are >55 years old with progesterone levels that are NOT in the luteal range. Obviously these women are also pre-screened to make sure they are not on hormones. We also offer follicular and ovulatory ranges for some hormones. These are based on fewer measurements of cycling women.
For estradiol, we use a 20th-80th percentile range. For progesterone, we use a 20th-90th percentile range (since modestly elevated progesterone is not as likely to be associated with issues compared to estrogen). That type of approach is used and a case-by-case approach is used for each hormone. For example, our range for 4-OH-E1 begins with zero (range = 0-80th percentile), not an actual value. We don’t want to tell anyone they are deficient for a carcinogenic estrogen! We also have age-dependent ranges for DHEA and testosterone (men only for T). Because our test methods are unique, we’re not able to tap into other studies done by others, but the ranges are based on extensive testing. Our actual reports show a woman’s reproductive hormones relative to both pre and postmenopausal ranges, which can be very helpful if you’re using HRT. The results shown here, for example, are from a postmenopausal woman who is obese. Her progesterone is where it belongs, but her estrogens are way high (up and into the premenopausal range) because she is inflamed and obese.
You will, from time to time, see an update to a reference range. Range changes are based on further evaluation of population data or method changes. As an example, we migrated our analysis of cortisol metabolites from a GC-MS/MS assay to an LC-MS/MS assay. The results are far more reproducible on an LC-MS/MS, but patient results come out slightly different. This resulted in a slight adjustment to the reference range.
Changes to reference ranges are not common for tests that have been established for years. A serum testosterone test might change its reference ranges if it shifts methods (from ELISA to LC-MS/MS, for example). The DUTCH test performs at a high level (reproducible and accurate) but we are engaged in an endless pursuit of improved performance and some of these improvements require slight adjustments to reference ranges.