If the steroid is used during a diagnostic injection (signified by the KX modifier), then that does not count towards the rolling 12-month limit. KX modifier should not be used for a therapeutic injection. However, if steroids are used in a diagnostic/therapeutic injection the duration between injections should be reflective of expected duration of response to the injectant used. That means if steroids are added to a second diagnostic injection it should be expected to last about 12 weeks.