Anne,
The article you cited mentions 'ITP' 79 times, and 'primary immune thrombocytopenia' only indirectly. However, your point is well-taken, that the expression is not entirely new. What is new is a trend among some writers toward leaving off the designation 'ITP', which runs counter to the guidelines in the article you cited:
The acronym ITP (now proposed to stand for immune thrombocytopenia) was preserved because of its widespread and time-honored use and taking into account its utility for literature searches.
Because some writers are leaving out the 'ITP' designation, I have been missing some important articles from my literature searches.
Therefore, I am no longer searching only on 'ITP', but also, on 'immune thrombcytopenia".