"Evaluation of Surveillance Bias and the Validity of the Venous Thromboembolism Quality Measure"  
JAMA Oct 9  
http://jama.jamanetwork.com/article.aspx?articleid=1748150 
"Conclusions and Relevance  Hospitals with higher quality scores had higher VTE prophylaxis rates but worse risk-adjusted VTE rates. Increased hospital VTE event rates were associated with increasing hospital VTE imaging use rates. Surveillance bias limits the usefulness of the VTE quality measure for hospitals working to improve quality and patients seeking to identify a high-quality hospital."