David A. Pfister, a Bay Area oncologist, was named “Best of the Bay Oncologist” in 2010 by KRON-TV, according to a Yelp reviewer. He was named one of America’s “Top Doctors” by US News, based on a “peer nomination process.” The biggest doctor rating site, at least in America, is HealthGrades. A HealthGrades survey of Dr. Pfister’s patients (n = 31) asked Would you recommend Dr. Pfister to family and friends? Dr. Pfister’s score — halfway between “mostly yes” and “definitely yes” — put him close to the national average.
The “Best of Bay” comment was one of seven Yelp reviews of Dr. Pfister that filtered out (= downgraded) by Yelp’s filtering algorithm. The filtered-out reviews were much more positive than the reviews that passed the filtering process. In the five passing reviews, Dr. Pfister received an average rating of 1 out of 5, with comments to match:
He was chronically late, and had poor time-management skills. . . . This was the third and final time that he’s made me wait at least an hour past my scheduled appointment time (requiring me to leave before seeing him). 
He was 30+ min late, unfriendly and unapologetic. His bedside manner is horrific and he talked me into having a procedure that ended up being painful and unnecessary. The office is completely disorganized. There are records of deceased patients out in the open in the bathroom. 
When I visit his office, the only thing he wishes to discuss with me are the results of my recent labs. If it were up to him, my appointment would last 2 minutes. . . All my other doctors have told me for years I should get my care elsewhere. Typical visits consists of 2 hours waiting, 5 minutes with the doctor. 
He is consistently late, as much as two hours, to his first appointments of the day. He arrives completely disheveled, hair sticking up and shirt untucked as if he was up half the night drinking. He also forgets your history and has to be reminded who you are, despite continual and regular appointments. Finally, if you ask questions he becomes very defensive and has even yelled at me for asking questions. 
Which view of Dr. Pfister is more accurate, KRON-TV or Yelp? In March 2012, his license was suspended. He “admitted he has a psychiatric problem and a substance abuse problem.” The Yelp reviews that passed the filtering algorithm, with their complaints about lateness, poor grooming, and disorganization, predicted the suspension (assuming that doctors with low yelp scores are more likely to be disciplined). HealthGrades has yet to figure out there is anything unusual about Dr. Pfister. He is not listed on vitals.com.
I came across Dr. Pfister while glancing through yelp ratings of Berkeley doctors. His low rating surprised me. A yelp reviewer linked to the license suspension.
My conclusion: When looking for a doctor, check yelp. Yelp’s filtering algorithm, which emphasized the low reviews, really works. In California, you can search state records for licensing board disciplinary actions but such actions are very rare.
Thanks to Bryan Castañeda for a long conversation about detecting bad doctors. In Unaccountable (which should have been on my Best Books of 2012 list), Marty Makary says that hospitals and surgeons are in many ways unaccountable for their mistakes. Yelp is a countervailing force.