Sepsis mimics among presumed sepsis patients at intensive care admission: a retrospective observational study

BACKGROUND

Diagnosing sepsis remains a challenge because of the lack of gold-standard diagnostics. Since there are no simple, broadly accepted criteria for infection, there is a risk of misclassifying sepsis patients (sepsis mimics) among patients with organ failure. The main objective of this study was to investigate the proportion of non-infected patients (sepsis mimics) in ICU patients with presumed sepsis at intensive care unit (ICU) admission.

METHODS

Adult patients were screened retrospectively during 3.5 years in four ICUs in Sweden for fulfilment of the sepsis-3 criteria at ICU admission (presumed sepsis). Proxy criteria for suspected infection were sampled blood culture(s) and concomitant antibiotic administration. Culture-negative presumed sepsis patients were screened for infection according to the Linder-Mellhammar Criteria of Infection (LMCI). Sepsis mimics were defined as without probable infection according to the LMCI. Confirmed sepsis was defined as presumed sepsis after the exclusion of sepsis mimics.

RESULTS

In the ICU presumed sepsis cohort (2664 patients), 25% were considered sepsis mimics. The most common reasons for ICU admission among sepsis mimics were acute heart failure and unspecific respiratory failure. Comparing sepsis mimics and confirmed sepsis showed that confirmed sepsis patients were slightly more severely ill but had similar mortality. C-reactive protein had modest discriminatory power (AUROC 0.71) with confirmed sepsis as the outcome.

CONCLUSIONS

One-fourth of a presumed ICU sepsis population identified with the sepsis-3 criteria could be considered sepsis mimics. The high proportion of sepsis mimics has a potential dilutional effect on the presumed sepsis population, which threatens the validity of results from sepsis studies using recommended sepsis criteria.

A simple mortality prediction model for sepsis patients in intensive care

Background

Sepsis is common in the intensive care unit (ICU). Two of the ICU's most widely used mortality prediction models are the Simplified Acute Physiology Score 3 (SAPS-3) and the Sequential Organ Failure Assessment (SOFA) score. We aimed to assess the mortality prediction performance of SAPS-3 and SOFA upon ICU admission for sepsis and find a simpler mortality prediction model for these patients to be used in clinical practice and when conducting studies.

Methods

A retrospective study of adult patients fulfilling the Sepsis-3 criteria admitted to four general ICUs was performed. A simple prognostic model was created using backward stepwise multivariate logistic regression. The area under the curve (AUC) of SAPS-3, SOFA and the simple model was assessed.

Results

One thousand nine hundred eighty four admissions were included. A simple six-parameter model consisting of age, immunosuppression, Glasgow Coma Scale, body temperature, C-reactive protein and bilirubin had an AUC of 0.72 (95% confidence interval (CI) 0.69-0.75) for 30-day mortality, which was non-inferior to SAPS-3 (AUC 0.75, 95% CI 0.72-0.77) (p = 0.071). SOFA had an AUC of 0.67 (95% CI 0.64-0.70) and was inferior to SAPS-3 (p < 0.001) and our simple model (p = 0.0019).

Conclusion

SAPS-3 has a lower prognostic value in sepsis than in the general ICU population. SOFA performs less well than SAPS-3. Our simple six-parameter model predicts mortality just as well as SAPS-3 upon ICU admission for sepsis, allowing the design of simple studies and performance monitoring.

[The Swecrit Biobank, associated clinical registries, and machine learning (artificial intelligence) improve critical care knowledge]

The unique Swecrit Biobank and its associated clinical registries for sepsis, ARDS, cardiac arrest, trauma, and COVID-19 include more than 150,000 blood samples and descriptions of critically ill patients. These assets provide a unique opportunity to research and improve the care of the most seriously ill patients through biomarker analyses, proteomic studies, and genetic and epigenetic studies using modern machine learning techniques (artificial intelligence). Interested researchers are invited to submit their proposals and participate.

Circulating dipeptidyl peptidase 3 on intensive care unit admission is a predictor of organ dysfunction and mortality

Background

Our aim was to investigate the prognostic potential of circulating dipeptidyl peptidase 3 (cDPP3) to predict mortality and development of organ dysfunction in a mixed intensive care unit (ICU) population, and for this reason, we analysed prospectively collected admission blood samples from adult ICU patients at four Swedish hospitals. Blood samples were stored in a biobank for later batch analysis. The association of cDPP3 levels with 30-day mortality and Sequential Organ Failure Assessment (SOFA) scores on day two was investigated before and after adjustment for the simplified acute physiology score III (SAPS-3), using multivariable (ordinal) logistic regression. The predictive power of cDPP3 was assessed using the area under the receiver operating characteristic curve (AUROC).

Results

Of 1978 included consecutive patients in 1 year (2016), 632 fulfilled the sepsis 3-criteria, 190 were admitted after cardiac arrest, and 157 because of trauma. Admission cDPP3 was independently (of SAPS-3) associated with 30-day mortality with odds ratios of 1.45 (95% confidence interval (CI) 1.28–1.64) in the entire ICU population, 1.30 (95% CI 1.08–1.57) in the sepsis subgroup and 2.28 (95% CI 1.50–3.62) in cardiac arrest. For trauma, there was no clear association. Circulating DPP3 alone was a moderate predictor of 30-day mortality with AUROCs of 0.68, 0.62, and 0.72 in the entire group, the sepsis subgroup, and the cardiac arrest subgroup, respectively. By adding cDPP3 to SAPS-3, AUROC improved for the entire group, the sepsis subgroup, and the cardiac arrest subgroup (p = 0.023).

Conclusion

Circulating DPP3 on admission is a SAPS-3 independent prognostic factor of day-two organ dysfunction and 30-day mortality in a mixed ICU population and needs further evaluation.

Supplementary Information

The online version contains supplementary material available at (10.1186/s40560-021-00561-9).

Plasma proenkephalin A 119-159 on intensive care unit admission is a predictor of organ failure and 30-day mortality

BACKGROUND

Proenkephalin A 119-159 (penKid) has been suggested as a marker of renal failure and poor outcome. We aimed to investigate the association of penKid on ICU admission with organ dysfunction and mortality in a mixed ICU population. In this retrospective, observational study, admission penKid levels from prospectively collected blood samples of consecutive patients admitted to four Swedish ICUs were analysed. The association of penKid with day-two sequential organ failure assessment (SOFA) scores and 30-day mortality was investigated using (ordinal) logistic regression. The predictive power of penKid for 30-day mortality and dialysis was assessed using the area under the receiver operating characteristic curve (AUC).

RESULTS

Of 1978 included patients, 632 fulfilled the sepsis 3-criteria, 190 had a cardiac arrest, and 157 had experienced trauma. Admission penKid was positively associated with 30-day mortality with an odds ratio of 1.95 (95% confidence interval 1.75-2.18, p < 0.001), and predicted 30-day mortality in the entire ICU population with an AUC of 0.71 (95% confidence interval 0.68-0.73) as well as in the sepsis, cardiac arrest and trauma subgroups (AUCs of 0.61-0.84). Correction for admission plasma creatinine revealed that penKid correlated with neurological dysfunction.

CONCLUSION

Plasma penKid on ICU admission is associated with day-two organ dysfunction and predictive of 30-day mortality in a mixed ICU-population, as well as in sepsis, cardiac arrest and trauma subgroups. In addition to being a marker of renal dysfunction, plasma penKid is associated with neurologic dysfunction in the entire ICU population, and cardiovascular dysfunction in sepsis.

Circulating bioactive adrenomedullin as a marker of sepsis, septic shock and critical illness

Background

Biomarkers can be of help to understand critical illness and to identify and stratify sepsis. Adrenomedullin is a vasoactive hormone, with reported prognostic and potentially therapeutic value in sepsis. The primary aim of this study was to investigate the association of circulating bioactive adrenomedullin (bio-ADM) levels at intensive care unit (ICU) admission with mortality in sepsis patients and in a general ICU population. Secondary aims included the association of bio-ADM with organ failure and the ability of bio-ADM to identify sepsis.

Methods

In this retrospective observational study, adult patients admitted to one of four ICUs during 2016 had admission bio-ADM levels analysed. Age-adjusted odds ratios (OR) with 95% CI for log-2 transformed bio-ADM, and Youden’s index derived cut-offs were calculated. The primary outcome was 30-day mortality, and secondary outcomes included the need for organ support and the ability to identify sepsis.

Results

Bio-ADM in 1867 consecutive patients were analysed; 632 patients fulfilled the sepsis-3 criteria of whom 267 had septic shock. The median bio-ADM in the entire ICU population was 40 pg/mL, 74 pg/mL in sepsis patients, 107 pg/mL in septic shock and 29 pg/mL in non-septic patients. The association of elevated bio-ADM and mortality in sepsis patients and the ICU population resulted in ORs of 1.23 (95% CI 1.07–1.41) and 1.22 (95% CI 1.12–1.32), respectively. The association with mortality remained after additional adjustment for lactate in sepsis patients. Elevated bio-ADM was associated with an increased need for dialysis with ORs of 2.28 (95% CI 2.01–2.59) and 1.97 (95% CI 1.64–2.36) for the ICU population and sepsis patients, respectively, and with increased need of vasopressors, OR 1.33 (95% CI 1.23–1.42) (95% CI 1.17–1.50) for both populations. Sepsis was identified with an OR of 1.78 (95% CI 1.64–1.94) for bio-ADM, after additional adjustment for severity of disease. A bio-ADM cut-off of 70 pg/mL differentiated between survivors and non-survivors in sepsis, but a Youden’s index derived threshold of 108 pg/mL performed better.

Conclusions

Admission bio-ADM is associated with 30-day mortality and organ failure in sepsis patients as well as in a general ICU population. Bio-ADM may be a morbidity-independent sepsis biomarker.

Sepsis is underreported in Swedish intensive care units: A retrospective observational multicentre study

BACKGROUND

Sepsis is a common indication for admission to the intensive care unit (ICU). Since definitions vary across studies, comparisons of prevalence and outcomes have been challenging. We aimed to compare sepsis according to ICU discharge codes with sepsis according to Sepsis-3 criteria and to investigate the epidemiology of sepsis in the ICU. We hypothesized that sepsis using discharge codes is underreported.

METHODS

Adult ICU admissions to four ICUs in Sweden between 2015 and 2017 were screened for sepsis according to the Sepsis-3 criteria. Medical records were reviewed and data extracted from the Swedish Intensive Care Registry.

RESULTS

Of 5990 adult ICU patients, 28% fulfilled the Sepsis-3 criteria on admission, but only 31% of them had sepsis as the registered main diagnosis at ICU discharge. Of the 1654 Sepsis-3 patients, 38% met the septic shock criteria. The Sepsis-3 in-hospital mortality was 26% compared to 33% in patients with septic shock. The incidence rate for ICU-treated sepsis was 81 cases per 100 000 person-years. One in four had a positive blood culture, and 44% were culture negative.

CONCLUSION

This large Swedish multicentre study showed that 28% of adult ICU patients fulfilled the Sepsis-3 criteria, but only one third of them had sepsis according to ICU discharge codes. We could confirm our hypothesis, that sepsis is severely underreported in Swedish ICUs, and we conclude that discharge codes should not be used for quality control or research purposes.

C-reactive protein as a prognostic factor in intensive care admissions for sepsis: A Swedish multicenter study

PURPOSE

C-reactive protein (CRP) is not included in the major intensive care unit (ICU) prognostic tools such as the Simplified Acute Physiology Score (SAPS). We assessed CRP on ICU admission as a SAPS-3 independent risk marker for short-term mortality and length of stay (LOS) in ICU patients with sepsis.

MATERIALS AND METHODS

Adult ICU admissions satisfying the Sepsis-3 criteria to four southern Swedish hospitals were retrospectively identified and divided into a low CRP group (<100 mg/L) and a high CRP group (>100 mg/L) based on the admission CRP level. The standardized mortality ratio (SMR) was calculated.

RESULTS

A total of 851 admissions were included. The SMR was higher in the high CRP group (0.85 vs. 0.67, P = .001 in the whole sepsis group and 0.85 vs. 0.59, P = .003 in the culture-positive subgroup). The CRP levels also correlated with ICU and hospital LOS in survivors (P < .001 and P = .002), again independent of SAPS-3.

CONCLUSION

An admission CRP level >100 mg/L is associated with an increased risk of ICU and 30-day mortality as well as prolonged LOS in survivors, irrespective of morbidity measured with SAPS-3. Thus, CRP may be a simple, early marker for prognosis in ICU admissions for sepsis.

Integrative studies implicate matrix metalloproteinase-12 as a culprit gene for large-artery atherosclerotic stroke

BACKGROUND

Ischaemic stroke and coronary heart disease are important contributors to the global disease burden and share atherosclerosis as the main underlying cause. Recent evidence from a genome-wide association study (GWAS) suggested that single nucleotide polymorphisms (SNP) near the MMP12 gene at chromosome 11q22.3 were associated with large-vessel ischaemic stroke. Here, we evaluated and extended these results by examining the relationship between MMP12 and atherosclerosis in clinical and experimental studies.

METHODS AND RESULTS

Plasma concentrations of MMP12 were measured at baseline in 3394 subjects with high-risk for cardiovascular disease (CVD) using the Olink ProSeek CVD I array. The plasma MMP12 concentration showed association with incident cardiovascular and cerebrovascular events (130 and 67 events, respectively, over 36 months) and carotid intima-media thickness progression (P = 3.6 × 10^-5 ). A GWAS of plasma MMP12 concentrations revealed that SNPs rs499459, rs613084 and rs1892971 at chr11q22.3 were independently associated with plasma MMP12 (P < 5 × 10^-8 ). The lead SNPs showed associations with mRNA levels of MMP12 and adjacent MMPs in atherosclerotic plaques. MMP12 transcriptomic and proteomic levels were strongly significantly increased in carotid plaques compared with control arterial tissue and in plaques from symptomatic versus asymptomatic patients. By combining immunohistochemistry and proximity ligation assay, we demonstrated that MMP12 localizes to CD68 + macrophages and interacts with elastin in plaques. MMP12 silencing in human THP-1-derived macrophages resulted in reduced macrophage migration.

CONCLUSIONS

Our study supports the notion that MMP12 is implicated in large-artery atherosclerotic stroke, functionally by enhancing elastin degradation and macrophage invasion in plaques.

Gene expression signatures, pathways and networks in carotid atherosclerosis

BACKGROUND

Embolism from unstable atheromas in the carotid bifurcation is a major cause of stroke. Here, we analysed gene expression in endarterectomies from patients with symptomatic (S) and asymptomatic (AS) carotid stenosis to identify pathways linked to plaque instability.

METHODS

Microarrays were prepared from plaques (n = 127) and peripheral blood samples (n = 96) of S and AS patients. Gene set enrichment, pathway mapping and network analyses of differentially expressed genes were performed.

RESULTS

These studies revealed upregulation of haemoglobin metabolism (P = 2.20E-05) and bone resorption (P = 9.63E-04) in S patients. Analysis of subgroups of patients indicated enrichment of calcification and osteoblast differentiation in S patients on statins, as well as inflammation and apoptosis in plaques removed >1 month compared to <2 weeks after symptom. By prediction profiling, a panel of 30 genes, mostly transcription factors, discriminated between plaques from S versus AS patients with 78% accuracy. By meta-analysis, common gene networks associated with atherosclerosis mapped to hypoxia, chemokines, calcification, actin cytoskeleton and extracellular matrix. A set of dysregulated genes (LMOD1, SYNPO2, PLIN2 and PPBP) previously not described in atherosclerosis were identified from microarrays and validated by quantitative PCR and immunohistochemistry.

CONCLUSIONS

Our findings confirmed a central role for inflammation and proteases in plaque instability, and highlighted haemoglobin metabolism and bone resorption as important pathways. Subgroup analysis suggested prolonged inflammation following the symptoms of plaque instability and calcification as a possible stabilizing mechanism by statins. In addition, transcriptional regulation may play an important role in the determination of plaque phenotype. The results from this study will serve as a basis for further exploration of molecular signatures in carotid atherosclerosis.

Increased expression of heparanase in symptomatic carotid atherosclerosis

OBJECTIVE

Proliferation of smooth muscle cells (SMCs) can stabilize atherosclerotic lesions but the molecular mechanisms that regulate this process in humans are largely unknown. We have previously shown that heparan sulfate proteoglycans (HSPGs), such as perlecan, regulate SMC growth in animal models by modulating heparin-binding mitogens. Since perlecan is expressed at low levels in human atherosclerosis, we speculated that the effect of heparan sulfate (HS) in human disease was rather influenced by HS degradation and investigated the expression of heparanase (HPSE) in human carotid endarterectomies.

METHODS AND RESULTS

Gene expression analysis from 127 endarterectomies in the BiKE database revealed increased expression of HPSE in carotid plaques compared with normal arteries, and a further elevation in symptomatic lesions. Increased HPSE protein expression in symptomatic plaque tissue was verified by tissue microarrays. HPSE mRNA levels correlated positively with expression of inflammatory markers IL-18, RANTES and IL-1β, and also T-cell co-stimulatory molecules, such as B7.2, CD28, LFA-1 and 4-1BB. Previously reported single nucleotide polymorphisms within HPSE were associated with differential mRNA expression in plaques. Immunohistochemistry revealed that inflammatory cells were major producers of HPSE in plaque tissue. HPSE immunoreactivity was also observed in SMCs adjacent to the necrotic core and was co-localized to deposits of fibrin.

CONCLUSIONS

This study demonstrates increased expression of HPSE in human atherosclerosis associated with inflammation, coagulation and plaque instability. Since HS can regulate SMC proliferation and influence plaque stability, the findings suggest that HPSE degradation of HS take part in the regulation of SMC function in human atherosclerosis.