Measuring and improving quality has become a dominant issue in health care, with financial implications based on the results. A study published in the Annals of Surgery analyzed the degree to which surgical specialization affects outcomes, treating it as a continuous variable defined quantitatively by procedural diversity.
Researchers used three-year patient data from the National Surgical Quality Improvement Program for the Department of Surgery at Barnes Jewish Hospital. To quantify procedural specialization, Herfindahl-Hirschman indices for surgeons were calculated using billing codes. These indices were calculated according to three different levels of procedural aggregation. Using conditional logit models, they then examined the relationship between these indices and 30-day postoperative mortality rates.
Data showed that surgeon specialization was inversely related to mortality rates after adjusting for case volume when indices were calculated using medium procedural aggregation (odds ratio for mortality =
0.580 per 0.1 unit Herfindahl increase) or low aggregation (odds ratio for mortality = 0.510 per 0.1 unit Herfindahl increase). No relationship was observed at the high level of aggregation.
Researchers concluded that the procedural concentration component of surgical specialization is correlated with improved mortality rates independently of case volume.
However, how broadly or narrowly “specialization” is defined has an impact on this relationship.
Hall, BL, et al. The impact of surgeon specialization on patient mortality: examination of a continuous Herfindahl-Hirschman index. Annals of Surgery. 2009 May;249(5):708-16.