What is a “normal” AMH level? Impact of the (relatively) new AMH Gen II assay on what is considered the new “normal”.

Why is this important?

There is now a new assay that is available for measuring AMH – the AMH Gen II assay. Historically, there used to be two assay kits that were commercially available. These were the Diagnostic Systems Lab (DSL) and Immunotech (IOT) (also called the Immunotech Beckman Coulter (IBC)) assay. This caused a lot of confusion in the literature as half the papers were published using the DSL assay and the other half the IOT assay.

The crude values reported by authors and between papers can differ substantially, with the IOT assay giving values for AMH that are higher than those obtained with the DSL assay. Beckman Coulter has now consolidated the two companies and holds the international patent on measuring AMH. This means that from now on, they will be the sole providers of the assay. The new AMH Gen II assay is the ONLY assay that is now available commercially for measuring AMH. The “normal” values for AMH have therefore changed as discussed in this blog.

Background

Anti-mullerian hormone (AMH) is a marker of ovarian reserve commonly used in clinical practice. Low AMH levels indicate diminished ovarian reserve with production of low number of eggs and low pregnancy rates with IVF. High AMH levels predict a high ovarian response during IVF and risk of ovarian hyperstimulation syndrome. A major advantage of measuring AMH is that AMH levels are relatively stable across the menstrual cycle and between cycles. AMH levels will decline with age and have been used to predict onset of menopause.

Facts about the AMH Gen II assay

1. It is a hybrid of the previous two assays (combining the DSL antibodies with the calibration of the IOT standards).

2. There are two measurements that one needs to become familiar with. The first is the smallest amount that the assay can reliably detect to determine the presence or absence of AMH. This is the limit of detection (LoD) and is 0.08 ng/mL for AMH. The second is the smallest amount the assay can reliably measure quantitatively (how much of AMH is present). This is the limit of quantitation (LoQ) and is 0.16 ng/mL. This means that the AMH Gen II assay cannot reliably determine between 0 and 0.16 ng/mL and therefore values should not be reported below 0.16 ng/mL.

3. If a sample is stored for 7 days at room temperature, the value will be 4% different than a fresh sample.

4. If a sample is frozen and then thawed before analysis, there will be a 6% variation in values.

5. The AMH Gen II assay has been calibrated to the IOT standards, the values derived from the AMH Gen II will be essentially identical to those derived from the IOT assay.

6. The AMH Gen II assay will provide values approximately 40% higher than the DSL assay. This means that when interpreting papers based on the DSL kit, clinicians will need to increase the values by approximately 40%.

7. This conversion from DSL to AMH Gen II assay values is not constant at all values. AMH Gen II assay levels will be even higher with increasing AMH values.

8. The DSL assay used to use pmol/l. The IOT assay and the new AMH Gen II assay use ng/mL. It is possible to convert ng/mL to pmol/l by multiplying by 7.14 (e.g. 1 ng/mL = 7.14 pmol/l).

So, what is a “normal” AMH level?

In a previous blog, I have discussed a paper that presented data from 15,834 US women. Those AMH levels were measured using a variation of the DSL assay but were reported as ng/mL. Here is another table giving values on age-specific AMH levels using the IOT assay (similar to the AMH Gen II assay). There currently isn’t available a table for age specific AMH values using the new AMH Gen II assay.

As shown in the Table the 50th centile for a woman under age 30 is 4.10 ng/mL, ages 31 - 35 is 3.46 ng/mL. ages 36 - 40 is 3 ng/mL and so on.

There are problems reported in the literature with the new AMH Gen II assay. These will be discussed in a subsequent blog.