We Need Better Tools for Sepsis Surveillance

Update on Sepsis Epidemiology in the Era of COVID-19

Timely and accurate data on the epidemiology of sepsis is essential to inform public policy, clinical practice, and research priorities. Recent studies have illuminated several ongoing questions about sepsis epidemiology, including the incidence and outcomes of sepsis in non-Western countries and in specialized populations such as surgical patients, patients with cancer, and the elderly. There have also been new insights into the limitations of current surveillance methods using administrative data and increasing experience tracking sepsis incidence and outcomes using "big data" approaches that take advantage of detailed electronic health record data. The COVID-19 pandemic, however, has fundamentally changed the landscape of sepsis epidemiology. It has increased sepsis rates, helped highlight ongoing controversies about how to define sepsis, and intensified debate about the possible unintended consequences of overly rigid sepsis care bundles. Despite these controversies, there is a growing consensus that severe COVID-19 causing organ dysfunction is appropriate to label as sepsis, even though it is treated very differently from bacterial sepsis, and that surveillance strategies need to be modified to reliably identify these cases to fully capture and delineate the current burden of sepsis. This review will summarize recent insights into the epidemiology of sepsis and highlight several urgent questions and priorities catalyzed by COVID-19.

Surveillance Strategies for Tracking Sepsis Incidence and Outcomes

Sepsis is a leading cause of death and the target of intense efforts to improve recognition, management and outcomes. Accurate sepsis surveillance is essential to properly interpreting the impact of quality improvement initiatives, making meaningful comparisons across hospitals and geographic regions, and guiding future research and resource investments. However, it is challenging to reliably track sepsis incidence and outcomes because sepsis is a heterogeneous clinical syndrome without a pathologic reference standard, allowing for subjectivity and broad discretion in assigning diagnoses. Most epidemiologic studies of sepsis to date have used hospital discharge codes and have suggested dramatic increases in sepsis incidence and decreases in mortality rates over time. However, diagnosis and coding practices vary widely between hospitals and are changing over time, complicating the interpretation of absolute rates and trends. Other surveillance approaches include death records, prospective clinical registries, retrospective medical record reviews, and analyses of the usual care arms of randomized controlled trials. Each of these strategies, however, has substantial limitations. Recently, the US Centers for Disease Control and Prevention released an "Adult Sepsis Event" definition that uses objective clinical indicators of infection and organ dysfunction that can be extracted from most hospitals' electronic health record systems. Emerging data suggest that electronic health record-based clinical surveillance, such as surveillance of Adult Sepsis Event, is accurate, can be applied uniformly across diverse hospitals, and generates more credible estimates of sepsis trends than administrative data. In this review, we discuss the advantages and limitations of different sepsis surveillance strategies and consider future directions.

Sepsis trends: increasing incidence and decreasing mortality, or changing denominator?

Numerous studies suggest that the incidence of sepsis has been steadily increasing over the past several decades while mortality rates are falling. However, reliably assessing trends in sepsis epidemiology is challenging due to changing diagnosis and coding practices over time. Ongoing efforts by clinicians, administrators, policy makers, and patient advocates to increase sepsis awareness, screening, and recognition are leading to more patients being labeled with sepsis. Subjective clinical definitions and heterogeneous presentations also allow for wide discretion in diagnosing sepsis rather than specific infections alone or non-specific syndromes. These factors create a potential ascertainment bias whereby the inclusion of less severely ill patients in sepsis case counts over time leads to a perceived increase in sepsis incidence and decrease in sepsis mortality rates. Analyses that rely on administrative data alone are further confounded by changing coding practices in response to new policies, financial incentives, and efforts to improve documentation. An alternate strategy for measuring sepsis incidence, outcomes, and trends is to use objective and consistent clinical criteria rather than administrative codes or registries to identify sepsis. This is feasible using data routinely found in electronic health record systems, such as blood culture draws and sustained courses of antibiotics to identify infection and laboratory values, vasopressors, and mechanical ventilation to measure acute organ dysfunction. Recent surveillance studies using this approach suggest that sepsis incidence and mortality rates have been essentially stable over the past decade. In this review, we summarize the major epidemiologic studies of sepsis trends, potential biases in these analyses, and the recent change in the surveillance paradigm toward using objective clinical data from electronic health records to more accurately characterize sepsis trends.

Variation in Identifying Sepsis and Organ Dysfunction Using Administrative Versus Electronic Clinical Data and Impact on Hospital Outcome Comparisons

OBJECTIVES

Administrative claims data are commonly used for sepsis surveillance, research, and quality improvement. However, variations in diagnosis, documentation, and coding practices for sepsis and organ dysfunction may confound efforts to estimate sepsis rates, compare outcomes, and perform risk adjustment. We evaluated hospital variation in the sensitivity of claims data relative to clinical data from electronic health records and its impact on outcome comparisons.

DESIGN, SETTING, AND PATIENTS

Retrospective cohort study of 4.3 million adult encounters at 193 U.S. hospitals in 2013-2014.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sepsis was defined using electronic health record-derived clinical indicators of presumed infection (blood culture draws and antibiotic administrations) and concurrent organ dysfunction (vasopressors, mechanical ventilation, doubling in creatinine, doubling in bilirubin to ≥ 2.0 mg/dL, decrease in platelets to < 100 cells/µL, or lactate ≥ 2.0 mmol/L). We compared claims for sepsis prevalence and mortality rates between both methods. All estimates were reliability adjusted to account for random variation using hierarchical logistic regression modeling. The sensitivity of hospitals' claims data was low and variable: median 30% (range, 5-54%) for sepsis, 66% (range, 26-84%) for acute kidney injury, 39% (range, 16-60%) for thrombocytopenia, 36% (range, 29-44%) for hepatic injury, and 66% (range, 29-84%) for shock. Correlation between claims and clinical data was moderate for sepsis prevalence (Pearson coefficient, 0.64) and mortality (0.61). Among hospitals in the lowest sepsis mortality quartile by claims, 46% shifted to higher mortality quartiles using clinical data. Using implicit sepsis criteria based on infection and organ dysfunction codes also yielded major differences versus clinical data.

CONCLUSIONS

Variation in the accuracy of claims data for identifying sepsis and organ dysfunction limits their use for comparing hospitals' sepsis rates and outcomes. Using objective clinical data may facilitate more meaningful hospital comparisons.

Sepsis Surveillance Using Adult Sepsis Events Simplified eSOFA Criteria Versus Sepsis-3 Sequential Organ Failure Assessment Criteria

OBJECTIVES

Sepsis-3 defines organ dysfunction as an increase in the Sequential Organ Failure Assessment score by greater than or equal to 2 points. However, some Sequential Organ Failure Assessment score components are not routinely recorded in all hospitals' electronic health record systems, limiting its utility for wide-scale sepsis surveillance. The Centers for Disease Control and Prevention recently released the Adult Sepsis Event surveillance definition that includes simplified organ dysfunction criteria optimized for electronic health records (eSOFA). We compared eSOFA versus Sequential Organ Failure Assessment with regard to sepsis prevalence, overlap, and outcomes.

DESIGN

Retrospective cohort study.

SETTING

One hundred eleven U.S. hospitals in the Cerner HealthFacts dataset.

PATIENTS

Adults hospitalized in 2013-2015.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We identified clinical indicators of presumed infection (blood cultures and antibiotics) concurrent with either: 1) an increase in Sequential Organ Failure Assessment score by 2 or more points (Sepsis-3) or 2) 1 or more eSOFA criteria: vasopressor initiation, mechanical ventilation initiation, lactate greater than or equal to 2.0 mmol/L, doubling in creatinine, doubling in bilirubin to greater than or equal to 2.0 mg/dL, or greater than or equal to 50% decrease in platelet count to less than 100 cells/μL (Centers for Disease Control and Prevention Adult Sepsis Event). We compared area under the receiver operating characteristic curves for discriminating in-hospital mortality, adjusting for baseline characteristics. Of 942,360 patients in the cohort, 57,242 (6.1%) had sepsis by Sequential Organ Failure Assessment versus 41,618 (4.4%) by eSOFA. Agreement between sepsis by Sequential Organ Failure Assessment and eSOFA was good (Cronbach's alpha 0.81). Baseline characteristics and infectious diagnoses were similar, but mortality was higher with eSOFA (17.1%) versus Sequential Organ Failure Assessment (14.4%; p < 0.001) as was discrimination for mortality (area under the receiver operating characteristic curve, 0.774 vs 0.759; p < 0.001). Comparisons were consistent across subgroups of age, infectious diagnoses, and comorbidities.

CONCLUSIONS

The Adult Sepsis Event's eSOFA organ dysfunction criteria identify a smaller, more severely ill sepsis cohort compared with the Sequential Organ Failure Assessment score, but with good overlap and similar clinical characteristics. Adult Sepsis Events may facilitate wide-scale automated sepsis surveillance that tracks closely with the more complex Sepsis-3 criteria.

Incidence and Trends of Sepsis in US Hospitals Using Clinical vs Claims Data, 2009-2014

IMPORTANCE

Estimates from claims-based analyses suggest that the incidence of sepsis is increasing and mortality rates from sepsis are decreasing. However, estimates from claims data may lack clinical fidelity and can be affected by changing diagnosis and coding practices over time.

OBJECTIVE

To estimate the US national incidence of sepsis and trends using detailed clinical data from the electronic health record (EHR) systems of diverse hospitals.

DESIGN, SETTING, AND POPULATION

Retrospective cohort study of adult patients admitted to 409 academic, community, and federal hospitals from 2009-2014.

EXPOSURES

Sepsis was identified using clinical indicators of presumed infection and concurrent acute organ dysfunction, adapting Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) criteria for objective and consistent EHR-based surveillance.

MAIN OUTCOMES AND MEASURES

Sepsis incidence, outcomes, and trends from 2009-2014 were calculated using regression models and compared with claims-based estimates using International Classification of Diseases, Ninth Revision, Clinical Modification codes for severe sepsis or septic shock. Case-finding criteria were validated against Sepsis-3 criteria using medical record reviews.

RESULTS

A total of 173 690 sepsis cases (mean age, 66.5 [SD, 15.5] y; 77 660 [42.4%] women) were identified using clinical criteria among 2 901 019 adults admitted to study hospitals in 2014 (6.0% incidence). Of these, 26 061 (15.0%) died in the hospital and 10 731 (6.2%) were discharged to hospice. From 2009-2014, sepsis incidence using clinical criteria was stable (+0.6% relative change/y [95% CI, -2.3% to 3.5%], P = .67) whereas incidence per claims increased (+10.3%/y [95% CI, 7.2% to 13.3%], P < .001). In-hospital mortality using clinical criteria declined (-3.3%/y [95% CI, -5.6% to -1.0%], P = .004), but there was no significant change in the combined outcome of death or discharge to hospice (-1.3%/y [95% CI, -3.2% to 0.6%], P = .19). In contrast, mortality using claims declined significantly (-7.0%/y [95% CI, -8.8% to -5.2%], P < .001), as did death or discharge to hospice (-4.5%/y [95% CI, -6.1% to -2.8%], P < .001). Clinical criteria were more sensitive in identifying sepsis than claims (69.7% [95% CI, 52.9% to 92.0%] vs 32.3% [95% CI, 24.4% to 43.0%], P < .001), with comparable positive predictive value (70.4% [95% CI, 64.0% to 76.8%] vs 75.2% [95% CI, 69.8% to 80.6%], P = .23).

CONCLUSIONS AND RELEVANCE

In clinical data from 409 hospitals, sepsis was present in 6% of adult hospitalizations, and in contrast to claims-based analyses, neither the incidence of sepsis nor the combined outcome of death or discharge to hospice changed significantly between 2009-2014. The findings also suggest that EHR-based clinical data provide more objective estimates than claims-based data for sepsis surveillance.

Differences in reported sepsis incidence according to study design: a literature review

Background

Sepsis and severe sepsis are common conditions in hospital settings, and are associated with high rates of morbidity and mortality, but reported incidences vary considerably. In this literature review, we describe the variation in reported population-based incidences of sepsis and severe sepsis. We also examine methodological and demographic differences between studies that may explain this variation.

Methods

We carried out a literature review searching three major databases and reference lists of relevant articles, to identify all original studies reporting the incidence of sepsis or severe sepsis in the general population. Two authors independently assessed all articles, and the final decision to exclude an article was reached by consensus. We extracted data according to predetermined variables, including study country, sepsis definition, and data source. We then calculated descriptive statistics for the reported incidences of sepsis and severe sepsis. The studies were classified according to the method used to identify cases of sepsis or severe sepsis: chart-based (i.e. review of patient charts) or code-based (i.e. predetermined International Classification of Diseases [ICD] codes).

Results

Among 482 articles initially screened, we identified 23 primary publications reporting incidence of sepsis and/or severe sepsis in the general population. The reported incidences ranged from 74 to 1180 per 100,000 person-years and 3 to 1074 per 100,000 person-years for sepsis and severe sepsis, respectively. Most chart-based studies used the Bone criteria (or a modification hereof) and Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) study criteria to identify cases of sepsis and severe sepsis. Most code-based studies used ICD-9 codes, but the number of codes used ranged from 1 to more than 1200. We found that the incidence varied according to how sepsis was identified (chart-based vs. code-based), calendar year, data source, and world region.

Conclusion

The reported incidences of sepsis and severe sepsis in the general population varied greatly between studies. Such differences may be attributable to differences in the methods used to collect the data, the study period, or the world region where the study was undertaken. This finding highlights the importance of standardised definitions and acquisition of data regarding sepsis and severe sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-016-0237-9) contains supplementary material, which is available to authorized users.