Can we use a blood test to help identify this hard-to-see disease?
I use this test. It’s commonly seen that using this test is mostly a personal judgment made by individual doctors. I’d like to make the case that we can do better than that mostly because endometriosis is a very common disease and our efforts to identify it are abysmal.
What makes this a bad test for endo?
The major pitfall is that CA 125 isn’t unique to endometriosis. Look below at how many conditions both benign and malignant can produce an elevated CA 125. Endometrioma is one of the most specific conditions it’s elevated in, but there’s a lot of overlap. That’s why doctors are weary.
Because of the muddiness around where it’s found, some doctors think CA125 is dangerous to use. Mostly because it can cause anxiety given CA125 is an ovarian cancer marker. It’s kind of like a positive finding on a mammogram. Most mammograms need further testing after because they find false positives 70ish% of the time. Not a great outcome, but some of the best we got. Even with all the false positives and unnecessary biopsies, we mammogram anyway. It’s worth it.
For me, the same goes for endo and CA 125. Endo is a common condition, up to 20% of women have it, and it’s life ruining. It takes many years to diagnose. It’s worth exploring as many ways as possible to capture the condition sooner than later.
Who to test?
Infertility or subfertiilty
An estimated 25%–50% of women with infertility have endometriosis, and approximately 30%–50% of women with endometriosis have infertility.
Pelvic Pain, Painful Periods, Painful Sex
The hallmark symptoms of endo are pain and different kinds of pain.
Painful Bowel Movements or Urination
Endo is more likely found in people with IBS and Interstitial Cystitis.
*Ethnic background doesn’t seem to affect any of the results.
Is CA125 always positive for endo?
If you have elevated CA125 you’re more likely to have endo. You can rule it in.
Elevated endo does not mean you have to have elevated CA125. This is especially true for milder disease. 26% of people with mild disease are positive. 87% of severe disease are positive. We cannot rule out endo with normal CA125. It may still be lurking.
These numbers help frame the usefulness of CA125. We shouldn’t run wild screening everyone and their mother for endo. It’s not good at that. A targeted approach maximizes its usefulness.
Why am I less weary than most?
IF you’re going to use the test here are some guidelines:
- Test DURING menstruation. CA 125 is much higher during a menstrual bleed (days 2-4) in women with endo than in women without. It’s about the same between the two groups the rest of the month.
- If you’re going to confirm a positive test, measure only in the first half of the cycle, preferably at the same time to reduce natural, albeit insignificant, changes week to week.
- Test only women who present with symptoms of endometriosis – painful periods, pelvic pain, painful sex, infertility, and IBS-type symptoms (pain with bowel movements). If you hone in on this group your chances of picking up endo increase a lot.
- There isn’t much variance between different labs, so you can test anywhere.
- CA125 >30 U/ml is predictive of endometriosis in symptomatic women without evidence of any other concurrent gynecological disease. You’re 11 times more likely to have endo above this level.
- The higher the result >35 U/mL, the greater likelihood of advanced stage of endo including scarring (adhesions). CA125 levels were 20.30 (13.97–27.10) IU/mL, 39.40 (23.50–161.00) IU/mL and 102.00 (41.90–182.45) IU/mL in healthy control group, mild endometriosis and advanced endometriosis group, respectively.
- If the result is positive and an ultrasound has not already been done, get an ultrasound to rule out the other conditions that present with elevated CA125.
Below are results that most clinicians wouldn’t test for nor interpret positively for the patient. It might not seem like a big red flag.
Dr. Bobby Parmar
Naturopathic Physician
