Variation in Academic Medical Centers' Coding Practices for Postoperative Respiratory Complications: Implications for the AHRQ Postoperative Respiratory Failure Patient Safety Indicator

Background: The Agency for Healthcare Research and Quality Patient Safety Indicator (PSI) 11 uses International Classification of Disease, 9th Clinical Modification diagnosis code 518.81 ("Acute respiratory failure")—but not the closely related alternative, 518.5 ("Pulmonary insufficiency after trauma and surgery")— to detect cases of postoperative respiratory failure. We sought to determine whether hospitals vary in the use of 518.81 versus 518.5 and whether such variation correlates with coder beliefs. Study Design: We conducted a cross-sectional analysis of administrative data from July 2009 through June 2010 for UHC (formerly University HealthSystem Consortium)-affiliated centers to assess the use of diagnosis codes 518.81 and 518.5 in PSI 11-eligible cases. We also surveyed coders at these centers to evaluate whether variation in the use of 518.81 versus 518.5 might be linked to coder beliefs. We asked survey respondents which diagnosis they would use for 2 ambiguous cases of postoperative pulmonary complications and how much they agreed with 6 statements about the coding process. Results: UHC-affiliated centers demonstrated wide variation in the use of 518.81 and 518.5, ranging from 0 to 26 cases and 0 to 56 cases/1000 PSI 11-eligible hospitalizations, respectively. Of 56 survey respondents, 64% chose 518.81 and 30% chose 518.5 for a clinical scenario involving postoperative respiratory failure, but these responses were not associated with actual coding of 518.81 or 518.5 at the center level. Sixty-two percent of respondents agreed that they are constrained by the words that physicians use. Their self-reported likelihood of querying physicians to clarify the diagnosis was significantly associated with coding of 518.5 at the center level. Conclusions: The extent to which diagnosis code 518.81 is used relative to 518.5 varies considerably across centers, based on local coding practice, the specific wording of physician documentation, and coder-physician communication. To standardize the coding of postoperative respiratory failure, the 518.81 and 518.5 codes have recently been revised to make the available options clearer and mutually exclusive, which may improve the capacity of PSI 11 to discriminate true differences in quality of care.