Hi Bear,
I’ll take a crack at it, too.
1) Therapists have varying abilities to see narcissism and NPD. Some therapists do not have narcissism/NPD on their radar screen. (Some therapists are narcissistic or have NPD--and they are unable to see it in themselves. But that’s a different story.)
2) Most therapists want to like their patients, and they often unconsciously see them in the best light possible. Therefore some therapists miss the signs that their patient is narcissistic/has NPD.
3) When stories/incidents are presented about other people (family members, friends, bosses, co-workers), some therapists are very capable of correctly identifying NPD while others are not. Depending upon the stories, a good therapist can be 99% sure that the person being discussed is diagnosable, or at least highly narcissistic.
4) But not always. For example, sometimes people with personality disorders see therapists and their depictions of others are so inaccurate it is really hard to tell. A good therapist tries to factor that in and see through it.
5) If you tell patients that they are narcissistic or have NPD, there is a very good chance that person will be so injured they will diminish the therapist and not come back. In other words, they will only continue if you see them in a particularly positive light—and the people around them in a particularly negative light. In these cases, therapists struggle with what to do/say. Build trust to break the news later? Use denial? Hope it goes away? The vast majority of the time, the therapist, no matter how good or bad, will ultimately fail with these patients. But (in my experience) every now and again, with years and years of work, one has a success. Patients and therapists can and should be very proud of these rare occurrences—because it is, indeed, a life, a relationship(s), and a family rescued.
I hope this helps…
Richard