Modifier 52 for timed services

I was told that the AMA may have updated the guideline for modifier 52 as it applies to timed services. PT's and chiro's regularly use the 52 to report that a service was performed for less time than identified in the code description. In searching everywhere, I am unable to find a reference to this. Does anyone have information regarding this? Any links or direct references you can give me would be wonderful!

Thanks in advance.

Modifier 52 for timed services