Hi Steve. While a bone marrow biopsy (BMBX) isn’t necessary to diagnose ET, it can be a valuable tool in assessing the overall health of your wife’s bone marrow…the heart of the blood manufacturing site in the body.
You sound very much like my husband, he would have insisted the doctor go the extra mile too, and ask for a bone marrow biopsy. It likely would not change the direction of treatment though.
The doctor may also wait to see how your wife is responding to the hydroxy. A biopsy may be recommended if there are unusual symptoms or complications. Regular monitoring may be all that’s required if everything is responding as anticipated.
But it’s certainly within your rights to request a biopsy.

When is her next set of labs?