Comparison of trends in sepsis incidence and coding using administrative claims versus objective clinical data

Abstract

Background: National reports of a dramatic rise in sepsis incidence are largely based on analyses of administrative databases. It is unclear if these estimates are biased by changes in coding practices over time.

Methods: We calculated linear trends in the annual incidence of septicemia, sepsis, and severe sepsis at 2 academic hospitals from 2003 to 2012 using 5 different claims methods and compared case identification rates to selected objective clinical markers, including positive blood cultures, vasopressors, and/or lactic acid levels.

Results: The annual incidence of hospitalizations with sepsis claims increased over the decade, ranging from a 54% increase for the method combining septicemia, bacteremia, and fungemia codes (P < .001 for linear trend) to a 706% increase for explicit severe sepsis/septic shock codes (P = .001). In contrast, the incidence of hospitalizations with positive blood cultures decreased by 17% (P = .006), and hospitalizations with positive blood cultures with concurrent vasopressors and/or lactic acidosis remained stable (P = .098). The sensitivity of sepsis claims for capturing hospitalizations with positive blood cultures with concurrent vasopressors and/or lactic acidosis increased (P < .001 for all methods), whereas the proportion of septicemia hospitalizations with positive blood cultures decreased from 50% to 30% (P < .001).

Conclusions: The incidence of hospitalizations with sepsis codes rose dramatically while hospitalizations with corresponding objective clinical markers remained stable or decreased. Coding for sepsis has become more inclusive, and septicemia diagnoses are increasingly being applied to patients without positive blood cultures. These changes likely explain some of the apparent rise in sepsis incidence and underscore the need for more reliable surveillance methods.

Keywords: administrative coding; bloodstream infections; incidence; sepsis; septicemia.

Figure 1.

A, Annual incidence of hospitalizations with discharge codes for septicemia, sepsis (Martin definition), and severe sepsis (Angus, Dombrovskiy definitions). B, Annual incidence of hospitalizations with blood cultures positive for a significant pathogen, with or without concurrent vasopressors or lactic acidosis. Numbers at the end of each trend line represent the fitted average annual percentage change compared to the 2003 incidence rate, with associated 95% confidence intervals. Abbreviations: BC, blood culture; LA, lactic acidosis.

Figure 2.

Annual change from 2003 to 2012 in sensitivity of septicemia, Martin-defined sepsis, and severe sepsis codes for identifying hospitalizations with positive blood cultures with concurrent vasopressors and/or lactic acidosis (A), and positive predictive value for septicemia and Martin sepsis codes (septicemia + bacteremia + fungemia) for identifying hospitalizations with positive blood cultures (B). Numbers at the end of each trend line represent the fitted average annual percentage change, with associated 95% confidence intervals.