Genetics and proteomics: deciphering gene association studies in critical illness

Adults with septic shock and extreme hyperferritinemia exhibit pathogenic immune variation

Post-hoc subgroup analysis of the negative trial of interleukin-1β receptor antagonist (IL1RA) for septic shock suggested that patients with features of macrophage activation syndrome (MAS) experienced a 50% relative risk reduction for mortality with treatment. Here we seek a genetic basis for this differential response. From 1341 patients enrolled in the ProCESS trial of early goal directed therapy for septic shock, we selected 6 patients with MAS features and the highest ferritin, for whole exome sequencing (mean 24,030.7 ηg/ml, +/SEM 7,411.1). Eleven rare (minor allele frequency <5%) pathogenic or likely pathogenic variants causal for the monogenic disorders of Familial Hemophagocytic Lymphohistiocytosis, atypical Hemolytic Uremic Syndrome, Familial Mediterranean Fever, and Cryopyrin-associated Periodic Fever were identified. In these conditions, seven of the identified variants are currently targeted with IL1RA and four with anti-C5 antibody. Gene-targeted precision medicine may benefit this subgroup of patients with septic shock and pathogenic immune variation.

Feeding the Open Abdomen

BACKGROUND

The purpose of this study was to determine if early enteral nutrition improves outcome for trauma patients with an open abdomen (OA).

METHODS

Retrospective review was used to identify 78 patients who required an OA for >or=4 hospital days, survived, and had available nutrition data. Demographic data and nutrition data comprising enteral nutrition initiation day and daily % target goal were collected. Patients were divided into 2 groups: early enteral feeding (EEN), initiated <or=4 days within celiotomy; and late enteral feeding (LEN; >4 days). Outcomes included infectious complications, early closure of the abdominal cavity (<8 days from original celiotomy), and fistula formation.

RESULTS

Fifty-three of 78 (68%) patients were men, with a mean age of 35 years; 74% had blunt trauma. Forty-three of 78 (55%) patients had EEN, whereas 35 of 78 (45%) had LEN. There was no difference with respect to demographics, injury severity, or infectious complication rates. Thirty-two of 43 (74%) patients with EEN had early closure of the abdominal cavity, whereas 17 of 35 (49%) patients with late feeding had early closure (p = .02). Four of 43 (9%) patients with EEN demonstrated fistula formation, whereas 9 of 35 (26%) patients with late feeding formed fistulae (p = .05). The EEN group had lower hospital charges (p = .04) by more than $50,000.

CONCLUSIONS

EEN in the OA was associated with (1) earlier primary abdominal closure, (2) lower fistula rate, (3) lower hospital charges.

Validation of SAPS3 admission score and its customization for use in Korean intensive care unit patients: a prospective multicentre study

BACKGROUND AND OBJECTIVE

To externally validate the simplified acute physiology score 3 (SAPS3) and to customize it for use in Korean intensive care unit (ICU) patients.

METHODS

This is a prospective multicentre cohort study involving 22 ICUs from 15 centres throughout Korea. The study population comprised patients who were consecutively admitted to participating ICUs from 1 July 2010 to 31 January 2011.

RESULTS

A total of 4617 patients were enrolled. ICU mortality was 14.3%, and hospital mortality was 20.6%. The patients were randomly assigned into one of two cohorts: a development (n = 2309) or validation (n = 2308) cohort. In the development cohort, the general SAPS3 had good discrimination (area under the receiver operating characteristics curve = 0.829), but poor calibration (Hosmer-Lemeshow goodness-of-fit test H = 123.06, P < 0.001, C = 118.45, P < 0.001). The Australasia SAPS3 did not improve calibration (H = 73.53, P < 0.001, C = 70.52, P < 0.001). Customization was achieved by altering the logit of the original SAPS3 equation. The new equation for Korean ICU patients was validated in the validation cohort, and demonstrated both good discrimination (area under the receiver operating characteristics curve = 0.835) and good calibration (H = 4.61, P = 0.799, C = 5.67, P = 0.684).

CONCLUSIONS

General and regional Australasia SAPS3 admission scores showed poor calibration for use in Korean ICU patients, but the prognostic power of the SAPS3 was significantly improved by customization. Prediction models should be customized before being used to predict mortality in different regions of the world.

Healthcare disparities in critical illness

OBJECTIVE

To summarize the current literature on racial and gender disparities in critical care and the mechanisms underlying these disparities in the course of acute critical illness.

DATA SOURCES

MEDLINE search on the published literature addressing racial, ethnic, or gender disparities in acute critical illness, such as sepsis, acute lung injury, pneumonia, venous thromboembolism, and cardiac arrest.

STUDY SELECTION

Clinical studies that evaluated general critically ill patient populations in the United States as well as specific critical care conditions were reviewed with a focus on studies evaluating factors and contributors to health disparities.

DATA EXTRACTION

Study findings are presented according to their association with the prevalence, clinical presentation, management, and outcomes in acute critical illness.

DATA SYNTHESIS

This review presents potential contributors for racial and gender disparities related to genetic susceptibility, comorbidities, preventive health services, socioeconomic factors, cultural differences, and access to care. The data are organized along the course of acute critical illness.

CONCLUSIONS

The literature to date shows that disparities in critical care are most likely multifactorial involving individual, community, and hospital-level factors at several points in the continuum of acute critical illness. The data presented identify potential targets as interventions to reduce disparities in critical care and future avenues for research.

Ethnicity and sepsis characteristics and outcomes. Population based study

BACKGROUND

Two distinct ethnic groups live in Southern Israel: urban Jews and rural Bedouin Arabs. These groups differ in their socioeconomic status, culture and living environment, and are treated in a single regional tertiary care hospital. We hypothesized that these two ethnic groups have different patterns of sepsis-related intensive care admissions.

METHODS

The study included all adult patients admitted to the Soroka University Medical Center Intensive Care Units between January 2002 and December 2008, with a diagnosis of sepsis. Demographic data, medical history, and hospitalization and outcomes data were obtained. Primary outcome was all-cause mortality.

RESULTS

Jewish patients admitted to the ICU (1343, 87%) were on average 17 years older than Bedouin Arabs (199, 13%). For the population <65 years, Bedouin Arabs had slightly higher age-adjusted prevalence of ICU sepsis admissions than Jewish patients (39.5 vs. 43.0, p=0.25), while for the population >65 years there was a reverse trend (21.8 vs. 19.8 p=0.49). There were no differences in the type of organ failure, sepsis severity or length of hospitalization between the two groups. Twenty eight days/in-hospital mortality was 33.9% in Bedouin Arabs vs. 45.5% in Jews, p=0.004. Following adjustment for comorbidities, age and severity of the disease, survival was unrelated to ethnicity, both at 28 days (odds ratio for Bedouin Arabs 0.86, 95% CI 0.66-1.24) and following hospital discharge (hazard ratio 0.86, 95% 0.67-1.09).

CONCLUSIONS

Sepsis-related ICU admissions are more prevalent among Bedouin Arabs at younger age compared with the Jewish population. Adjusted for confounders, ethnicity does not influence prognosis.

Genetics and genomics in pediatric septic shock

OBJECTIVES

Pediatric septic shock continues to be an important public health problem. Several investigative groups have applied genetic and genomic approaches as a means of identifying novel pathways and therapeutic targets, discovery of sepsis-related biomarkers, and identification of septic shock subclasses. This review will highlight studies in pediatric sepsis with a focus on gene association studies and genome-wide expression profiling.

DATA SOURCES

A summary of published literature involving gene association and expression profiling studies specifically involving pediatric sepsis and septic shock.

SUMMARY

Several polymorphisms of genes broadly involved in inflammation, immunity, and coagulation have been linked with susceptibility to sepsis, or outcome of sepsis in children. Many of these studies involve meningococcemia, and the strongest association involves a functional polymorphism of the plasminogen activator inhibitor-1 promoter region and meningococcal sepsis. Expression profiling studies in pediatric septic shock have identified zinc supplementation and inhibition of matrix metalloproteinase-8 activity as potential, novel therapeutic approaches in sepsis. Studies focused on discovery of sepsis-related biomarkers have identified interleukin-8 as a robust outcome biomarker in pediatric septic shock. Additional studies have demonstrated the feasibility and clinical relevance of gene expression-based subclassification of pediatric septic shock.

CONCLUSIONS

Pediatric sepsis and septic shock are increasingly being studied by genetic and genomic approaches and the accumulating data hold the promise of enhancing our future approach to this ongoing clinical problem.

Genetic predictors of susceptibility to cutaneous fungal infections: a pilot genome wide association study to refine a candidate gene search

BACKGROUND

Trichophyton tonsurans is the foremost fungal pathogen of minority children in the U.S. Despite overwhelming infection rates, it does not appear that this fungus infects children in a non-specific manner.

OBJECTIVE

This study was designed to identify genes that may predispose or protect a child from T. tonsurans infection.

METHODS

Children participating in an earlier longitudinal study wherein infection rates could be reliably determined were eligible for inclusion. DNA from a subset (n=40) of these children at the population extremes underwent whole genome genotyping (WGG). Allele frequencies between cases and controls were examined and significant SNPs were used to develop a candidate gene list for which the remainder of the cohort (n=115) were genotyped. Cumulative infection rate was examined by genotype and the ability of selected genotypes to predict the likelihood of infection explored by multivariable analysis.

RESULTS

23 genes with a putative mechanistic role in cutaneous infection were selected for evaluation. Of these, 21 demonstrated significant differences in infection rate between genotypes. A risk index assigned to genotypes in the 21 genes accounted for over 60% of the variability observed in infection rate (adjusted r(2)=0.665, p<0.001). Among these, 8 appeared to account for the majority of variability that was observed (r(2)=0.603, p<0.001). These included genes involved in: leukocyte activation and migration, extracellular matrix integrity and remodeling, epidermal maintenance and wound repair, and cutaneous permeability.

CONCLUSIONS

Applying WGG to individuals at the extremes of phenotype can help to guide the selection of candidate genes in populations of small cohorts where disease etiology is likely polygenic in nature.

Austrian validation and customization of the SAPS 3 Admission Score

OBJECTIVE

To test the prognostic performance of the SAPS 3 Admission Score in a regional cohort and to empirically test the need and feasibility of regional customization.

DESIGN

Prospective multicenter cohort study.

PATIENTS AND SETTING

Data on a total of 2,060 patients consecutively admitted to 22 intensive care units in Austria from October 2, 2006 to February 28, 2007.

MEASUREMENTS AND RESULTS

The database includes basic variables, SAPS 3, length-of-stay and outcome data. The original SAPS 3 Admission Score overestimated hospital mortality in Austrian intensive care patients through all strata of the severity-of-illness. This was true for both available equations, the General and the Central and Western Europe equation. For this reason a customized country-specific model was developed, using cross-validation techniques. This model showed excellent calibration and discrimination in the whole cohort (Hosmer-Lemeshow goodness-of-fit: H = 4.50, P = 0.922; C = 5.61, P = 0.847, aROC, 0.82) as well as in the various tested subgroups.

CONCLUSIONS

The SAPS 3 Admission Score's general equation can be seen as a framework for addressing the problem of outcome prediction in the general population of adult ICU patients. For benchmarking purposes, region-specific or country-specific equations seem to be necessary in order to compare ICUs on a similar level.

Racial variation in the incidence, care, and outcomes of severe sepsis: analysis of population, patient, and hospital characteristics

RATIONALE

Higher rates of sepsis have been reported in minorities.

OBJECTIVES

To explore racial differences in the incidence and associated case fatality of severe sepsis, accounting for clinical, social, health care service delivery, and geographic characteristics.

METHODS

Retrospective population-based cohort study using hospital discharge and U.S. Census data for all persons (n = 71,102,655) living in 68 hospital referral regions in six states.

MEASUREMENTS AND MAIN RESULTS

Age-, sex- and race-standardized severe sepsis incidence and inpatient case fatality rates, adjusted incidence rate ratios, and adjusted intensive care unit (ICU) admission and case fatality rate differences. Of 8,938,111 nonfederal hospitalizations, 282,292 had severe sepsis. Overall, blacks had the highest age- and sex-standardized population-based incidence (6.08/1,000 vs. 4.06/1,000 for Hispanics and 3.58/1,000 for whites) and ICU case fatality (32.1 vs. 30.4% for Hispanics and 29.3% for whites, P < 0.0001). Adjusting for differences in poverty in their region of residence, blacks still had a higher population-based incidence of severe sepsis (adjusted rate ratio, 1.44 [95% CI, 1.42-1.46]) than whites, but Hispanics had a lower incidence (adjusted rate ratio, 0.91 [0.90-0.92]). Among patients with severe sepsis admitted to the ICU, adjustments for clinical characteristics and the treating hospital fully explained blacks' higher ICU case fatality.

CONCLUSIONS

Higher adjusted black incidence and the lower Hispanic incidence may reflect residual confounding, or it could signal biologic differences in susceptibility. Focused interventions to improve processes and outcomes of care at the hospitals that disproportionately treat blacks could narrow disparities in overall mortality from severe sepsis.

Pharmacogenetics and paediatric drug development: issues and consequences to labelling and dosing recommendations

The area of pharmacogenetics (PGt) is evolving rapidly. However, ongoing efforts in this field are not aligned with the requirements for the inclusion of clinically relevant findings into the label, especially with reference to paediatric indications. Clinical research in children poses unique issues from a practical and technical perspective, but many challenges can be overcome by applying advanced study design and data analysis methods. When investigating the role of PGt factors on treatment effect, all features that influence drug response must be taken into account. Yet, PGt often has a privileged status in research protocols, with PGt factors evaluated independently from other determinants of response, instead of being regarded as other demographic or clinical covariates (e.g., age, renal function). At present, guidelines to incorporate PGt findings into label statements are lacking in part because this is a new and incompletely understood area. This situation is no longer acceptable. To achieve the potential that PGt can offer to drug development and ultimately to drug prescription, academia, industry and regulatory agencies need to pool resources on the revision of study design and data analysis requisites, bringing in model-based methodologies to enable accurate interpretation of results and provide appropriate labelling recommendations.