If you are a Pakistani or Pakistani-American, how likely is it that you would identify yourself as an Asian Indian in any survey, questionnaire, AMCAS application, day-to-day life, etc? From the many Pakistanis that I know, few to none would in most circumstances. Most Pakistanis would put down Pakistani, Asian, other Asian, or simply Other. However, that's anecdotal and based on my own experiences.
According to the Educational Commission for Foreign Medical Graduates, Indians are the largest group of foreign doctors. There are over 50,000 Indian doctors (from India) without including the Indian-American and permanent resident Indian doctors. Pakistanis have around 12,000 doctors from Pakistan, without including Pakistani-American and permanent resident Pakistanis. In fact, there are more Filipino doctors from the Philippines than Pakistani. Furthermore, there are more Mexican doctors from Mexico than Pakistani doctors. So there are more of a particular group of URMs than there are Pakistanis in medicine.
You can find out more info by looking at the 2000 Census, the ECFMG records, the AAPI website, and even http://en.wikipedia.org/wiki/International_medical_graduate#United_States