Objective The epidemiology of severe sepsis is derived from administrative databases that rely on ICD-9-CM codes to select cases. We compared the sensitivity of two code-abstraction methods in identifying severe sepsis cases using a severe sepsis registry. Design Single center retrospective cohort study Setting Tertiary care, Academic, University Hospital Patients 1735 patients with severe sepsis or septic shock Interventions None Measurements Proportion identified as severe sepsis using two code-abstraction methods, (1) the new specific ICD-9 codes for severe sepsis and septic shock, and (2) a validated method requiring two ICD-9 codes for infection and end-organ dysfunction. Multivariable logistic regression was performed to determine sociodemographics and clinical characteristics associated with documentation and coding accuracy. Main Results The strategy combining a code for infection and end-organ dysfunction was more sensitive in identifying cases than the method requiring specific ICD-9 codes for severe sepsis or septic shock (47% vs. 21%). Elevated serum lactate level, (p<0.001), ICU admission (p<0.001), presence of shock (p<0.001), bacteremia as the source of sepsis (p=0.02), and increased APACHE II score (p<0.001) were independently associated with being appropriately documented and coded. The 28-day mortality was significantly higher in those who were accurately documented/coded (41%, compared to 14% in those who were not, p<0.001), reflective of a more severe presentation on admission. Conclusions Patients admitted with severe sepsis and septic shock were incompletely documented and under-coded, using either ICD-9 code abstracting method. Documentation of severe sepsis using the new sepsis codes was more common in more severely ill patients. These findings are important when evaluating current national estimates and when interpreting epidemiologic studies of severe sepsis as cohorts derived from claims-based strategies appear to be biased towards a more severely ill patient population.

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