Background: Research techniques using administrative data have been used to assess quality of care in the management of appendicitis, but their validity has not been assessed. This study assessed the validity of a research technique using administrative data to determine whether patients undergoing an appendectomy actually had appendicitis or if they had a negative appendectomy (NA).
Materials and methods: A retrospective study of patients at Group Health Cooperative of Puget Sound undergoing appendectomy from 1991-1999 was conducted to compare the accuracy of administrative codes with data abstracted from medical records.
Results: Of 1823 nonincidental appendectomies (mean age 31 +/- 18.6 years, 49.6% female), 280 did not have appendicitis by criteria applied to administrative data (15.4%). The accuracy of this method for determining appendicitis was determined by medical record evaluation revealing sensitivity (98.6%), specificity (48.6%), positive predictive value for appendicitis (83.8%), and negative predictive value for NA (70.4%). When the administrative-data technique did not classify a patient as having had appendicitis, chart-abstracted data indicated appendicitis in 6.4%, and an incorrectly labeled incidental appendectomy in 23.2%. The administrative-data technique for detecting NA erroneously included many cases of incidental appendectomy and missed many cases of clinically confirmed NA. More than half of clinical NAs were missed by the administrative technique.
Conclusions: In this setting, the sensitivity of administrative-data techniques for the detection of appendicitis was excellent, but their adequacy for identifying patients undergoing NA was limited. The use of this technique as a quality measure should be reconsidered.