Association of iron status with the risk of bloodstream infections: results from the prospective population-based HUNT Study in Norway

Iron deficiency and infection risk in Danish blood donors

BACKGROUND

We aimed to investigate if iron deficiency was associated with infection susceptibility in a large cohort of healthy individuals.

STUDY DESIGN AND METHODS

The Danish Blood Donor Study is a national ongoing prospective study of blood donors. We included 94,628 donors with 338,290 ferritin measurements from March 2010 to October 2022. We performed sex-stratified multivariable Cox regression to estimate the risk of infection for iron-deficient donors compared with iron-replete donors. Infection was defined as either a filled prescription of antibiotics registered in the Danish National Prescription Registry (NPR), or a hospital contact with infection registered in the Danish National Patient Registry (DNPR).

RESULTS

Iron deficiency was associated with an overall increased risk of infection (defined as prescriptions of antibiotics) for women (hazard ratio [HR] 1.08, 95% confidence interval [CI] 1.02-1.15). Subgroup analyses showed an increased risk of respiratory tract infections (HR 1.16, 95% CI 1.05-1.28) and urinary tract infections (HR 1.16, 95% CI 1.04-1.29). Iron deficiency was not associated with overall risk of infection for men (HR 1.02, 95% CI 0.82-1.28). For both men and women, no association was found between iron deficiency and hospital contacts for infections.

CONCLUSION

Iron deficiency was associated with an increased risk of infection in female blood donors. However, effect sizes were small, and there was no association between iron deficiency and hospital contacts for infection. Consequently, risk of infection should not be considered an apprehension regarding blood donation. These findings support the role of iron in immune function and monitorization of iron stores in female blood donors.

Role of nutrition in diabetes mellitus and infections

In this editorial, we have commented on the article that has been published in the recent issue of World Journal of Clinical Cases. The authors have described a case of unilateral thyroid cyst and have opined that the acute onset of infection may be linked to diabetes mellitus (DM). We have focused on the role of nutrition in the association between DM and infection. Patients with DM are at a high risk of infection, which could also be attributed to nutrition-related factors. Nutritional interventions for patients with diabetes are mainly based on a low-calorie diet, which can be achieved by adhering to a low-carbohydrate diet. However, dietary fiber supplementation is recommended to maintain the diversity of the gut microbiota. Furthermore, high-quality protein can prevent the increased risk of infection due to malnutrition. Supplementation of vitamins C, vitamins A, vitamins D, and folic acid improves blood sugar control and facilitates immune regulation. Mineral deficiencies augment the risk of infection, but the relationship with diabetes is mostly U-shaped and a good intake should be maintained.

Iron, hemochromatosis genotypes, and risk of infections: a cohort study of 142 188 general population individuals

ABSTRACT

It is unclear whether risk of infection is increased in individuals with hereditary hemochromatosis and in individuals with low or high plasma iron, transferrin saturation, or ferritin. Therefore, we tested whether high and low iron, transferrin saturation, and ferritin are associated with risk of infections observationally and genetically through HFE genotypes. We studied 142 188 Danish general population individuals. Iron, transferrin saturation, and ferritin were measured in 136 656, 136 599, and 38 020 individuals, respectively. HFE was genotyped for C282Y and H63D in 132 542 individuals. Median follow-up after study enrollment was 8 years (range, 0-38) for hospital and emergency room admissions with infections (n = 20 394) using the National Patient Register, covering all Danish hospitals. Hazard ratios for any infection were 1.20 (95% confidence interval [CI], 1.12-1.28) and 1.14 (95% CI, 1.07-1.22) in individuals with plasma iron ≤5th or ≥95th percentile compared with individuals with iron from 26th to 74th percentiles. Findings for transferrin saturation were similar, whereas infection risk was not increased in individuals with ferritin ≤5th or ≥95th percentile. Hazard ratios in C282Y homozygotes vs noncarriers were 1.40 (95% CI, 1.16-1.68) for any infection, 1.69 (95% CI, 1.05-2.73) for sepsis, and 2.34 (95% CI, 1.41-3.90) for death from infectious disease. Risk of infection was increased in C282Y homozygotes with normal plasma iron, transferrin saturation, or ferritin, and in C282Y homozygotes without liver disease, diabetes, and/or heart failure. In summary, low and high plasma iron and transferrin saturation were independently associated with increased infection risk. C282Y homozygotes had increased risk of any infection, sepsis, and death from infections. Even C282Y homozygotes with normal iron, transferrin saturation, or ferritin, not currently recommended for genotyping, had increased infection risk.

Protocol for deep mining the correlation between acute pancreatitis and ferroptosis using the MIMIC-III database and STATA software

The limitations associated with distinguishing serum Fe2+ and Fe3+ hinder the widespread application of ferroptosis, beyond laboratory settings. Here, we present a protocol for deep mining the correlation between acute pancreatitis and ferroptosis using the MIMIC-III database and STATA software. We describe steps for using Cox regression, decision curve analysis (DCA), and receiver operating characteristic (ROC) approaches to establish the relationship between them and determine the relevant factors. This protocol has potential application in establishing novel research models that integrate both fundamental and clinical methodologies. For complete details on the use and execution of this protocol, please refer to Yueling Deng et al.1.

Impact of Iron Profile and Vitamin D Levels on Clinical Outcomes in Patients with Sepsis and Septic Shock: A Cross-sectional Analysis at a Tertiary Care Center

Aim and background

Sepsis is a major global health affecting millions worldwide, hence understanding its contributing factors becomes paramount. This cross-sectional study at a tertiary care center explores the relationship between iron profile, vitamin D levels, and outcomes in sepsis and septic shock patients. The primary objective was to explore the prevalence of iron profile and vitamin D parameters during early intensive care unit (ICU) admission and their association with 28-day mortality.

Materials and methods

Spanning 18 months, the study enrolled adult patients meeting sepsis or septic shock criteria at the ICU. Data collection included demographic information, clinical characteristics, and blood samples for iron profile and vitamin D levels at admission. Disease severity was assessed using sequential organ failure assessment (SOFA) and acute physiology and chronic health evaluation II (APACHE II) scores, and treatment was administered as per surviving sepsis-3 guidelines.

Results

The research involved 142 participants, uncovering prevalent organisms such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Noteworthy connections to mortality were identified for factors including vasopressor support, ICU stay duration, SOFA score, and APACHE-II score. Interestingly, age, gender, and vitamin D levels showed no significant associations. However, the study did reveal a significant association between iron, ferritin, and transferrin saturation levels with increased 28-day mortality.

Conclusion

Our study concluded that low Iron, elevated ferritin, and decreased transferrin saturation levels maintained associations with the outcome of interest. While no such relationship was established with vitamin D levels. These results suggest potential implications for patient management and prognosis, warranting further exploration in future research.

How to cite this article

Bairwa M, Jatteppanavar B, Kant R, Singh M, Choudhury A. Impact of Iron Profile and Vitamin D Levels on Clinical Outcomes in Patients with Sepsis and Septic Shock: A Cross-sectional Analysis at a Tertiary Care Center. Indian J Crit Care Med 2024;28(6):569-574.

Circulating micronutrient levels and their association with sepsis susceptibility and severity: a Mendelian randomization study

Background: Sepsis, a global health challenge, necessitates a nuanced understanding of modifiable factors for effective prevention and intervention. The role of trace micronutrients in sepsis pathogenesis remains unclear, and their potential connection, especially with genetic influences, warrants exploration. Methods: We employed Mendelian randomization (MR) analyses to assess the causal relationship between genetically predicted blood levels of nine micronutrients (calcium, β-carotene, iron, magnesium, phosphorus, vitamin C, vitamin B6, vitamin D, and zinc) and sepsis susceptibility, severity, and subtypes. The instrumental variables for circulating micronutrients were derived from nine published genome-wide association studies (GWAS). In the primary MR analysis, we utilized summary statistics for sepsis from two independent databases (UK Biobank and FinnGen consortium), for initial and replication analyses. Subsequently, a meta-analysis was conducted to merge the results. In secondary MR analyses, we assessed the causal effects of micronutrients on five sepsis-related outcomes (severe sepsis, sepsis-related death within 28 days, severe sepsis-related death within 28 days, streptococcal septicaemia, and puerperal sepsis), incorporating multiple sensitivity analyses and multivariable MR to address potential heterogeneity and pleiotropy. Results: The study revealed a significant causal link between genetically forecasted zinc levels and reduced risk of severe sepsis-related death within 28 days (odds ratio [OR] = 0.450; 95% confidence interval [CI]: 0.263, 0.770; p = 3.58 × 10-3). Additionally, suggestive associations were found for iron (increased risk of sepsis), β-carotene (reduced risk of sepsis death) and vitamin C (decreased risk of puerperal sepsis). No significant connections were observed for other micronutrients. Conclusion: Our study highlighted that zinc may emerges as a potential protective factor against severe sepsis-related death within 28 days, providing theoretical support for supplementing zinc in high-risk critically ill sepsis patients. In the future, larger-scale data are needed to validate our findings.

Serum iron fluctuations link ferroptosis process with mortality and prognosis of acute pancreatitis

Recently, the existence of ferroptosis has been confirmed in chronic pancreatitis. However, its role in acute pancreatitis (AP) process, especially in critical status, has not yet been mentioned. To verify this hypothesis, we included 873 AP patients (training set) and 1,188 NAFLD patients (internal validation set) selected from MIMIC-III (Medical Information Mark for Intensive Care) database and 218 AP patients (external validation set) in Linshui County People's Hospital ICU data. We analyzed the correlation between mortality and ferroptosis associating factors (such as serum iron, ALP, lactate, etc.) in them through regression analysis. In addition, to test the significance of these factors, the nomogram, AUC, and DCA analysis were applied. The results showed that serum iron, IBC, ALP, and lactate (p < 0.05) were independent factors for the mortality and prognosis of these patients. These correlations suggest ferroptosis and follow-up cell programmed death may own an important clinical interference significance among this population.

Insomnia symptoms and risk of bloodstream infections: prospective data from the prospective population-based Nord-Trøndelag Health Study (HUNT), Norway

Previous research suggests decreased immune function and increased risk of infections in individuals with insomnia. We examined the effect of insomnia symptoms on risk of bloodstream infections (BSIs) and BSI-related mortality in a population-based prospective study. A total of 53,536 participants in the second Norwegian Nord-Trøndelag Health Study (HUNT2) (1995-97) were linked to prospective data on clinically relevant BSIs until 2011. In Cox regression, we estimated hazard ratios (HRs) with 95% confidence intervals (CIs) for a first-time BSI and for BSI-related mortality (BSI registered ≤30 days prior to death) associated with insomnia symptoms. Compared with participants who reported "no symptoms", participants reporting having "difficulty initiating sleep" (DIS) often/almost every night had a HR for a first-time BSI of 1.14 (95% CI 0.96-1.34). Participants reporting "difficulties maintaining sleep" (DMS) often/almost every night had a HR of 1.19 (95% CI 1.01-1.40), whereas those having a feeling of "non-restorative sleep" once a week or more had a HR of 1.23 (95% CI 1.04-1.46). Participants frequently experiencing all three of the above symptoms had a HR of 1.39 (1.04-1.87), whilst those who had both DIS and DMS had a HR of 1.15 (0.93-1.41) and being troubled by insomnia symptoms to a degree that affected work performance was associated with a HR of 1.41 (95% CI 1.08-1.84). The HRs for BSI-related mortality suggest an increased risk with increasing insomnia symptoms, but the CIs are wide and inconclusive. We found that frequent insomnia symptoms and insomnia symptoms that affected work performance were associated with a weak positive increased risk of BSI.

Iron Status and NAFLD among European Populations: A Bidirectional Two-Sample Mendelian Randomization Study

Background and aim: Previous observational studies have suggested a paradoxical relationship between iron status and the risk of non-alcoholic fatty liver disease (NAFLD). Observed associations in these epidemiological studies fail to show sequential temporality and suffer from problems of confounding. Therefore, we performed a bidirectional two-sample Mendelian randomization (MR) to evaluate the relationship between serum iron status and NAFLD. Methods: The inverse weighted method (IVW) meta-analysis with the fixed-effect model was the main method to estimate the relationship between iron status, including serum ferritin, iron, transferrin saturation (TSAT) and total iron-binding capacity (TIBC), and NAFLD. Weighted median, penalized weighted median, and MR Robust Adjusted Profile Score (MR RAPS) methods were used as additional analyses. Sensitivity analyses were performed with Cochran's Q test, MR-Egger regression, Steiger filtering, and the MR PRESSO test. Results: Iron status, including serum ferritin, iron, and TSAT, was associated with an increased risk of NAFLD (odds ratio (OR) (95% confidence interval (CI)): 1.25 (1.06, 1.48); 1.24 (1.05, 1.46), 1.16 (1.02, 1.31), respectively). In contrast, minimal effects of NAFLD on serum ferritin, iron, TSAT, and TIBC were observed (OR (95% CI): 1.01 (1.00, 1.02), 1.01 (1.00, 1.02), 1.03 (1.01, 1.05), 1.03 (1.01, 1.05), respectively). Conclusions: Our findings corroborated the causal associations between serum ferritin, iron, TSAT, and NAFLD, which might suggest the potential benefits of iron-related therapy. In addition, NAFLD might, in turn, slightly affect iron homeostasis indicated as serum ferritin, iron, TSAT, and TIBC, but this needs to be further confirmed.

Iron status and the risk of sepsis and severe COVID-19: a two-sample Mendelian randomization study

Observational studies have indicated an association between iron status and risk of sepsis and COVID-19. We estimated the effect of genetically-predicted iron biomarkers on risk of sepsis and risk of being hospitalized with COVID-19, performing a two-sample Mendelian randomization study. For risk of sepsis, one standard deviation increase in genetically-predicted serum iron was associated with odds ratio (OR) of 1.14 (95% confidence interval [CI] 1.01-1.29, P = 0.031). The findings were supported in the analyses for transferrin saturation and total iron binding capacity, while the estimate for ferritin was inconclusive. We found a tendency of higher risk of hospitalization with COVID-19 for serum iron; OR 1.29 (CI 0.97-1.72, P = 0.08), whereas sex-stratified analyses showed OR 1.63 (CI 0.94-2.86, P = 0.09) for women and OR 1.21 (CI 0.92-1.62, P = 0.17) for men. Sensitivity analyses supported the main findings and did not suggest bias due to pleiotropy. Our findings suggest a causal effect of genetically-predicted higher iron status and risk of hospitalization due to sepsis and indications of an increased risk of being hospitalized with COVID-19. These findings warrant further studies to assess iron status in relation to severe infections, including the potential of improved management.

Thyroid function and risk of bloodstream infections: Results from the Norwegian prospective population-based HUNT Study

OBJECTIVE

Previous studies on thyroid function and risk of infection is conflicting and often stem from intensive care cohorts were nonthyroidal illness syndrome (NTIS) may be present. The objective of this study was to identify the risk of bloodstream infections (BSI) and BSI-related mortality with thyroid-stimulating hormone (TSH) levels within the reference range in a general population.

DESIGN

Prospective follow-up.

PARTICIPANTS

The HUNT2 (1995-97) included 34,619 participants with information on TSH levels.

MEASUREMENTS

Hazard ratios (HRs) with 95% confidence interval (CI) confirmed BSIs and BSI-related mortality until 2011.

RESULTS

During a median follow-up of 14.5 years, 1179 experienced at least one episode of BSI and 208 died within 30 days after a BSI. TSH levels within the reference range of 0.5-4.5 mU/L were not associated with the risk of first-time BSI, with an HR of 0.97 (95% CI: 0.90-1.04) per mU/L. Stratified by baseline age < or ≥65 years, TSH was inversely associated with the risk of BSI (HR: 0.88; 95% CI: 0.78-1.00 per mU/L) in the youngest age group only. Persons with any baseline thyroid disease had a 30% risk and the hyperthyroid subgroup a 57%, and hypothyroidism a 20% increased risk of BSI. TSH levels were not clearly associated with BSI mortality, but the HRs were imprecise due to few BSI-related deaths.

CONCLUSION

There was some evidence of a weak inverse association between TSH levels and the risk of BSI in persons below 65 years of age. The increased risk seen in persons with thyroid illness is probably explained by confounding by concurrent ill health.

Explaining sex differences in risk of bloodstream infections using mediation analysis in the population-based HUNT study in Norway

Previous studies indicate sex differences in incidence and severity of bloodstream infections (BSI). We examined the effect of sex on risk of BSI, BSI mortality, and BSI caused by the most common infecting bacteria. Using causal mediation analyses, we assessed if this effect is mediated by health behaviours (smoking, alcohol consumption), education, cardiovascular risk factors (systolic blood pressure, non-HDL cholesterol, body mass index) and selected comorbidities. This prospective study included 64,040 participants (46.8% men) in the population-based HUNT2 Survey (1995-1997) linked with hospital records in incident BSI. During median follow-up of 15.2 years, 1840 (2.9%) participants (51.3% men) experienced a BSI and 396 (0.6%) died (56.6% men). Men had 41% higher risk of first-time BSI (95% confidence interval (CI), 28-54%) than women. Together, health behaviours, education, cardiovascular risk factors and comorbidities mediated 34% of the excess risk of BSI observed in men. The HR of BSI mortality was 1.87 (95% CI 1.53-2.28), for BSI due to S. aureus 2.09 (1.28-2.54), S. pneumoniae 1.36 (1.05-1.76), E. coli 0.97 (0.84-1.13) in men vs women. This study shows that men have higher risk of BSI and BSI mortality than women. One-third of this effect was mediated by potential modifiable risk factors for incident BSI.

Polymicrobial bacteremia due to Lactobacillus jensenii and Veillonella montpellierensis in a pregnant patient; case report and review of literature

Prompt and accurate diagnosis of polymicrobial bacteremia, which causes the difficulty in anti-infective treatments, poor treatment outcome and high mortality, is essential for initiating effective antimicrobial therapy. Here we present a case of bacteremia caused by two types of uncommon bacteria, Lactobacillus jenseniand and Veillonella montpellierensis in a 29-year-old pregnant woman at 33 weeks of gestation with anemia due to iron deficiency. She had no comorbidity or other chronic illnesses and was successfully treated with appropriate antibiotic use.

Iron Deficiency and Incident Infections among Community-Dwelling Adults Age 70 Years and Older: Results from the DO-HEALTH Study

OBJECTIVES

To assess if baseline iron deficiency, with or without anemia, is associated with incident infections over 3 years among community-dwelling older adults.

DESIGN

Prospective secondary analysis of DO-HEALTH, a 3-year randomized, double-blind controlled trial.

SETTING AND PARTICIPANTS

2157 community-dwelling adults age 70+ from 5 European countries with good cognitive function and mobility and no major health events in the 5 years prior to enrollment Measurements: Incident infections, their severity and type were recorded every 3 months throughout the 3-year follow-up. Iron deficiency was defined as soluble transferrin receptor (sTfR) levels > 28.1 nmol/l and anemia as hemoglobin levels < 120 g/l for women and 130 g/l for men. We applied negative binomial mixed effects regression models with random effects for countries, and controlling for treatment allocation, age, sex, body mass index, polypharmacy, number of comorbidities, smoking status, living situation, alcohol intake, frailty status, and physical activity levels. A pre-defined stratified analysis was performed to explore if the associations between iron deficiency and infections were consistent by baseline anemia status.

RESULTS

In total, 2141 participants were included in the analyses (mean age 74.9 years, 61.5% of women, 26.8% with iron deficiency). Across all participants, baseline iron deficiency was not associated with incident overall infections, but was associated with a 63% greater rate of incident severe infections requiring hospitalization (incidence rate ratio [IRR] 1.63, 95% Confidence Interval [CI] 1.11-2.41, p=0.01). This association was more pronounced among the 2000 participants who did not have anemia at baseline (IRR=1.80, 95% CI 1.20-2.69, p=0.005).

CONCLUSION

Based on this prospective study among generally healthy European community-dwelling older adults, iron deficiency was not associated with the incidence rate of overall infections but may increase the incidence of severe infections. Intervention studies are needed to prove the causality of this observation.

Genome-Wide Linkage Analysis of the Risk of Contracting a Bloodstream Infection in 47 Pedigrees Followed for 23 Years Assembled From a Population-Based Cohort (the HUNT Study)

OBJECTIVES

Bloodstream infection is an important cause of death worldwide. The main objective of this study was to identify genetic loci linked to risk of contracting a bloodstream infection.

DESIGN

Genome-wide linkage analysis.

SETTING

Population-based, Norwegian cohort, followed between 1995 and 2017.

SUBJECTS

Among 69,423 genotyped subjects, there were 47 families with two or more second-degree relatives with bloodstream infection in the follow-up period. There were 365 subjects in these families, of which 110 were affected.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The cohort was genotyped using Illumina HumanCoreExome (Illumina, San Diego, CA) arrays. Before linkage analysis, single-nucleotide polymorphisms were pruned and clumped. In nonparametric linkage analysis using an exponential model, we found three loci with a suggestive linkage to bloodstream infection, all on chromosome 4, at 46.6 centimorgan (logarithm of odds, 2.3), 57.7 centimorgan (logarithm of odds, 3.2), and 70.0 centimorgan (logarithm of odds, 2.1). At the peak of the lead region are three genes: TLR10, TLR1, and TLR6.

CONCLUSIONS

Variations in the TLR10/1/6 locus appear to be linked with the risk of contracting a bloodstream infection.

Association between iron status and the risk of adverse outcomes in COVID-19

BACKGROUND & AIMS

Iron is an essential trace element to almost all organism, and the delicate balance between host defend system and viral proliferation plays an important role in infective conditions. While the association of the iron metabolism with the prognosis of COVID-19 remains poorly understood. We aimed to estimate the associations of systemic iron metabolism parameters with the severity and risks of adverse outcomes in COVID-19.

METHODS

In this retrospective cohort study, we included 158 confirmed COVID-19 patients in Tongji Hospital, Wuhan, China (27 January to 5 April, 2020). Demographic data, comorbidities, laboratory examinations, treatments, and clinical outcomes were all collected. Multivariable Poisson regression was used to estimate the association of iron parameter levels with the severity and risks of adverse outcomes in COVID-19 patients.

RESULTS

We identified 60 (38%) severe cases in 158 COVID-19 patients. The median age was 63 years (interquartile range [IQR]: 54-73) and the median length of hospital stay was 28 days (IQR: 17-40). After adjusting for age, sex, IL-6, and pre-existing comorbidities, all iron parameters were associated with the severity of COVID-19 with adjusted risk ratio of 0.42 [95% CI: 0.22-0.83], 4.38 [95% CI: 1.86-10.33], 0.19 [95% CI: 0.08-0.48], and 0.25 [95% CI: 0.10-0.58] for serum iron, ferritin, transferrin, and total iron-binding capacity, respectively. These iron indices were also related to the risk of ARDS, coagulopathy, acute cardiac injury, acute liver injury, and acute kidney injury in COVID-19 patients and high cytokine concentrations.

CONCLUSIONS

Patients with low serum iron status likely suffered from severe condition and multiple-organ injury in COVID-19. The iron metabolism parameters might be risk factors and clinical biomarkers for COVID-19 prognosis.

How Severe Anaemia Might Influence the Risk of Invasive Bacterial Infections in African Children

Severe anaemia and invasive bacterial infections are common causes of childhood sickness and death in sub-Saharan Africa. Accumulating evidence suggests that severely anaemic African children may have a higher risk of invasive bacterial infections. However, the mechanisms underlying this association remain poorly described. Severe anaemia is characterized by increased haemolysis, erythropoietic drive, gut permeability, and disruption of immune regulatory systems. These pathways are associated with dysregulation of iron homeostasis, including the downregulation of the hepatic hormone hepcidin. Increased haemolysis and low hepcidin levels potentially increase plasma, tissue and intracellular iron levels. Pathogenic bacteria require iron and/or haem to proliferate and have evolved numerous strategies to acquire labile and protein-bound iron/haem. In this review, we discuss how severe anaemia may mediate the risk of invasive bacterial infections through dysregulation of hepcidin and/or iron homeostasis, and potential studies that could be conducted to test this hypothesis.

Iron deficiency after kidney transplantation

Iron deficiency (ID) is highly prevalent in kidney transplant recipients (KTRs) and has been independently associated with an excess mortality risk in this population. Several causes lead to ID in KTRs, including inflammation, medication and an increased iron need after transplantation. Although many studies in other populations indicate a pivotal role for iron as a regulator of the immune system, little is known about the impact of ID on the immune system in KTRs. Moreover, clinical trials in patients with chronic kidney disease or heart failure have shown that correction of ID, with or without anaemia, improves exercise capacity and quality of life, and may improve survival. ID could therefore be a modifiable risk factor to improve graft and patient outcomes in KTRs; prospective studies are warranted to substantiate this hypothesis.

Iron Administration, Infection, and Anemia Management in CKD: Untangling the Effects of Intravenous Iron Therapy on Immunity and Infection Risk

Patients with chronic kidney disease (CKD) are at increased risk for infection, attributable to immune dysfunction, increased exposure to infectious agents, loss of cutaneous barriers, comorbid conditions, and treatment-related factors (eg, hemodialysis and immunosuppressant therapy). Because iron plays a vital role in pathogen reproduction and host immunity, it is biologically plausible that intravenous iron therapy and/or iron deficiency influence infection risk in CKD. Available data from preclinical experiments, observational studies, and randomized controlled trials are summarized to explore the interplay between intravenous iron and infection risk among patients with CKD, particularly those receiving maintenance hemodialysis. The current evidence base, including data from a recent randomized controlled trial, suggests that proactive judicious use of intravenous iron (in a manner that minimizes the accumulation of non-transferrin-bound iron) beneficially replaces iron stores while avoiding a clinically relevant effect on infection risk. In the absence of an urgent clinical need, intravenous iron therapy should be avoided in patients with active infection. Although serum ferritin concentration and transferrin saturation can help guide clinical decision making about intravenous iron therapy, definition of an optimal iron status and its precise determination in individual patients remain clinically challenging in CKD and warrant additional study.

Causal associations of iron status with gout and rheumatoid arthritis, but not with inflammatory bowel disease

BACKGROUND & AIMS

We conducted a two-sample Mendelian randomization study to assess the associations of iron homeostasis with the risk of gout, rheumatoid arthritis and inflammatory bowel disease.

METHODS

Single-nucleotide polymorphisms for iron status were selected at the genome-wide significance level from a large genome-wide association study of 48 972 European-descent individuals. Summary-level data for gout, rheumatoid arthritis and inflammatory bowel disease were obtained from The Global Urate Genetics Consortium and two large genome-wide association studies, respectively. Inverse-variance weighted method with random-effects and sensitivity analyses were performed.

RESULTS

Genetic predisposition to high iron status was causally associated with higher odds of gout, lower odds of rheumatoid arthritis, but not associated with inflammatory bowel disease. The odds ratios of gout were 1.35 (95% confidence interval (CI), 1.00, 1.81; p = 0.047), 2.07 (95% CI, 1.23, 3.50; p = 0.006), 1.27 (95% CI, 1.07, 1.50; p = 0.007) and 0.69 (95% CI, 0.54, 0.90; p = 0.005) per one standard deviation increment of serum iron, ferritin, transferrin saturation, and transferrin levels, respectively. For rheumatoid arthritis, the corresponding odds ratios were 0.79 (95% CI, 0.65, 0.94; p = 0.010), 0.59 (95% CI, 0.40, 0.86; p = 0.007), 0.84 (95% CI, 0.75, 0.94; p = 0.003) and 1.28 (95% CI, 1.06, 1.55; p = 0.012).

CONCLUSIONS

Based on consistent findings for four iron biomarkers, genetically high iron status was positively associated with gout and inversely associated with rheumatoid arthritis. There was limited MR evidence supporting a causal association between iron status and inflammatory bowel disease.

Population-based risk factors for community-onset bloodstream infections

Although a number of comorbidities have been associated with development of bloodstream infection, actual risk factors have not been well defined and quantified in nonselected populations. We sought to quantify population-based risk factors for development of community-onset bloodstream infection (COBSI). Surveillance was conducted among all residents of the Western Interior of British Columbia, Canada, during 2011-2018. Risks were expressed as incidence rate ratios (IRR) with 95% confidence intervals (CI). The annual incidence was 147.1 per 100,000 and older individuals, and males were at overall higher risk. The median Charlson score was 2 (IQR, 0-3), and this was higher among those with healthcare-associated (2; IQR, 1-4) as compared to community-associated (1; IQR, 0-2; P < 0.0001) COBSI. Risk factors for development of COBSI included (IRR; 95% CI): HIV infection (8.89; 5.17-14.27), cancer (6.80; 6.13-7.54), congestive heart failure (4.68; 4.00-5.46), dementia (3.31; 2.82-3.87), diabetes mellitus (3.10; 2.80-3.42), cerebrovascular accident (2.79; 2.34-3.31), renal dysfunction (2.75; 2.33-3.22), chronic lung disease (2.03; 1.79-2.28), peripheral vascular disease (1.68; 1.39-2.01), and rheumatic disease (1.44; 1.14-1.79). Patients with multiple comorbid illnesses were older, more likely to be male, and have healthcare-associated BSI, higher rates of antimicrobial resistance, and different clinical foci of infection. A number of demographic and comorbid conditions significantly increase the risk for development of COBSI.

Ferumoxytol Attenuates the Function of MDSCs to Ameliorate LPS-Induced Immunosuppression in Sepsis

Sepsis-induced immunosuppression is recognized as one of the main features responsible for therapeutic failures. Myeloid-derived suppressor cells (MDSCs), which are mainly characterized by their suppressive properties, have been reported to be expanded in sepsis. Ferumoxytol (FMT), an FDA-approved iron supplement, has been shown to possess immune-modulatory properties in tumors. However, it is unclear whether FMT alters the functions of MDSCs to reduce late-sepsis immunosuppression. Here, we showed an immunomodulatory effect of FMT on MDSCs to ameliorate lipopolysaccharide (LPS)-induced immunosuppression in the late stage of sepsis. Separation of cells with internalized FMT and detection of the intracellular iron content showed that MDSCs could uptake FMT. Low doses of FMT had no effects on the cell viability of MDSCs, but FMT inhibited the expansion of MDSCs in vitro. Moreover, FMT significantly downregulated the expression levels of Arg-1, S100A8, S100A9, and p47phox as well as ROS production in MDSCs. FMT decreased the percentage of granulocytic MDSCs (G-MDSCs) and promoted the differentiation of MDSCs into macrophages. Furthermore, FMT reduced white blood cell recruitment and alveolar wall thickening in the lungs and areas of necrosis in the liver as well as some biochemical markers of liver dysfunction. FMT decreased the percentage of G-MDSCs and monocytic MDSCs (M-MDSCs) in the spleens of LPS-induced septic mice. Of note, FMT reduced the T cell immunosuppressive functions of both G-MDSCs and M-MDSCs. Expectedly, FMT also significantly reduced Arg-1 and p47phox gene expression in splenic CD11b⁺Gr-1⁺ cells isolated from LPS-challenged mice. These data indicate that FMT decreased the immunosuppressive functions of MDSCs by decreasing Arg-1 and ROS production, suggesting that FMT may reduce long-term immunosuppression in the late stage of sepsis.

Risk of bacteremia in hospitalised patients with inflammatory bowel disease: a 9-year cohort study

BACKGROUND

Patients with inflammatory bowel disease might be at increased risk of invasive bacterial infections.

OBJECTIVES

The objective of this study was to identify the rate of bacteremia in hospitalised patients with inflammatory bowel disease and risk factors.

METHODS

An observational cohort of hospitalised patients with inflammatory bowel disease, aged 16-80 years, from 2008 to 2017 in a large tertiary hospital. Patients with Charlson comorbidity index of 2 or greater were excluded. Patients with one or more positive blood culture were reviewed. Logistic regression was used to evaluate risk factors for bacteremia.

RESULTS

Of 5522 admitted patients, only 1.3% had bacteremia (73/5522) (39, Crohn's disease; 25, ulcerative colitis; nine, unclassified inflammatory bowel disease). The most common pathogen was Escherichia coli (19/73 patients). The mortality rate at 30 days of patients with bacteremia was 13.7% (10/73). Longer hospitalisations (mean length of stay (21.6 ± 31.0 vs. 6.4 ± 16.0 days; P < 0.0001) and older age (mean age 47.5 ± 18.0 vs. 40.2 ± 15.4 years, P < 0.0001)) were associated with an increased risk of bacteremia. In multivariate analysis, treatment with either anti-tumour necrosis factor α, purine analogues, steroids or amino salicylates was not associated with an increased risk of bacteremia. Risk was greatest among patients aged 65 years or older (relative risk 2.84, 95% confidence interval 1.6-4.8; P = 0.0001) relative to those under 65 years.

CONCLUSION

Age over 65 years, but not inflammatory bowel disease-related medications, is associated with an increased risk of bacteremia in hospitalised patients with inflammatory bowel disease.

Iron Metabolism: An Emerging Therapeutic Target in Critical Illness

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.