Is there any way to verify that I'm not seeing the cached results from the items api?

Best way to verify is to invalidate the cache if anything is changed on item record.

You can force cache misses by attaching a random/unused URL parameter to the end of the URL. Eg, "[your URL]&foo=123". Once "123" is used, you'll need to use a new number next time. Programatically, you can use something like Date.now()