Validity of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) Screening for Sepsis in Surgical Mortalities

Abstract

BACKGROUND: Sepsis is among the leading causes of death in the United States. The Agency for Healthcare Research and Quality uses International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) billing code screening for the identification of sepsis. We investigated the incidence of sepsis in mortality at our academic medical center through ICD-9-CM screening of billing codes corresponding to sepsis and compared this approach for accuracy using physician chart review as the gold-standard. METHODS: Two hundred forty-three surgical mortalities between January 2012 and January 2013 were reviewed by a Performance Improvement team. All mortalities were screened and evaluated for sepsis using physician chart review and ICD-9-CM codes for sepsis (995.91), severe sepsis (995.92), and septic shock (785.52). RESULTS: Unexpected mortalities were associated with higher rates of sepsis and expected mortalities than anticipated (p<0.0001). A total of 40.6% of patients with sepsis suffered from more than one infection; the most common infectious sources were intra-abdominal (43.5%), blood stream (40.3%), and pulmonary (38.7%) infections. Screening by ICD-9-CM identified sepsis in 23.0% of mortalities, and physician review identified sepsis in 25.5% of mortalities. The sensitivity and specificity of ICD-9-CM screening were 82.3% and 78.3%, respectively. The positive and negative predictive values were 91.1% and 62.1%, respectively. CONCLUSION: Sepsis is a common concurrent condition in surgical patients who die unexpectedly. Screening by ICD-9-CM for sepsis is accurate in identifying patients with sepsis but misses the identification of all patients with sepsis. The diagnostic accuracy of ICD-9-CM screening for sepsis is currently not adequate for public reporting or benchmarking, and is useful only as a guide for institutional quality improvement.