When is high MPO a concern?

@keithl56 MPO is just one tool a physician uses to measure increased risk of cardiovascular issues. By itself it is an indicator, but the test is usually done as port of a panel that measures other risk factors. You do not mention your wife's age or overall health, but you did say all other tests are normal, so I think that is why your physician is taking a watchful approach. Here is what the Cleveland Clinic Heart Lab has to say about high MPO:
https://www.clevelandheartlab.com/wp-content/uploads/2016/01/Inflammation-Tests_Patients.pdf
Is your wife using blood pressure medications, statins or other strategies to help lower her cardiovascular risks?

My wife is a very healthy active 71 YO. Plays pickle ball several times per week, walks, and does yoga. LDL is also on the high side, but not that bad. Most websites that I have referenced concur with the following statement:

"A high MPO level, which some laboratories consider greater than 539 pmol/L, signifies substantial inflammation and a heightened risk for a heart attack or stroke in the near future. This risk is independent, meaning it provides information beyond what is learned from cholesterol panels or blood pressure readings."

Hence my concern. Based on this I would have expected a more aggressive approach.

@keithl56 Statins have two convenient qualities or actions: they stabilize existing plaque by calcifying it...into place....and they also have an anti-inflammatory effect.

Perhaps a panel yielding a CRP score would help to situate this one indicator which is not apparently supported by the rest of the information the physician used.

The CRP score was within normal range. I've been on statins since they came out about 40 years ago due to hypercholesterolemia and while I have a CAC of almost 1300 at least, I know that my plaque is for the most part stable (asymptomatic). Given that statins are generally beneficial I'm not sure why the PCP just doesn't recommend them now. I don't see any downside, and it may help lower the MPO. I've never experienced any side effects and I've used mevacor, zocor, lipitor, and now crestor. I've only changed when the efficacy has dropped despite dosage increases. I have been on 20mg of crestor for many years without the need to increase the dose, although I also use zetia.

I have heard that this test is very sensitive especially if you have a cold or not feeling well. Also there are very specific timeframes the lab has to test the blood for an accurate reading. Maybe get it retested in a month or two.