Severe Sepsis Cohorts Derived From Claims-Based Strategies Appear to be Biased Toward a More Severely Ill Patient Population*

Abstract

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.

Hospital Incidence and Mortality Rates of Sepsis: An Analysis of Hospital Episode (DRG) Statistics in Germany From 2007 to 2013

“…In general, the exclusive examination of ICD-10-based sepsis codes that are assigned on discharge can yield estimates of the frequency of sepsis that are lower, by a factor of 2.3 to 6, than those derived from a prospective evaluation of patients' hospital charts (19,34). Some cases of sepsis are coded wrongly or not at all (35,36). Some pathogen-based codes, however, are not unequivocally linked to sepsis, and thus some of the patients who receive these codes (probably a very small fraction) do not, in fact, have sepsis.…”

Post–Acute Care Use and Hospital Readmission after Sepsis

“…We collected sociodemographics, comorbid conditions, hospitalizations in the prior year, and hospitalization details. We previously reviewed medical records to ensure the quality of the administrative data using this approach (18) and reviewed a sample of cases and each variable for quality assurance for the present study.…”

“…In the first one, we used the explicit ICD-9-specific codes for severe sepsis and septic shock (995.92 and 785.52, respectively). In the second, we used an implicit approach requiring ICD-9-CM codes for infection, including the 038 family of codes for septicemia, and end-organ dysfunction via the Angus method (18)(19)(20). Because septicemia could identify cases of sepsis or severe sepsis, we did not integrate septicemia codes into our explicit approach.…”

“…We discriminated sepsis from nonsepsis hospitalizations using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), codes based on administrative data (18)(19)(20). Sepsis was defined using three validated approaches to capture the spectrum of disease severity (18)(19)(20).…”

“…Sepsis was defined using three validated approaches to capture the spectrum of disease severity (18)(19)(20). We identified cases of sepsis using the explicit ICD-9-CMspecific code method (995.91) for sepsis.…”