Outcome Prediction of Acute Kidney Injury Biomarkers at Initiation of Dialysis in Critical Units

Current role of biomarkers in the initiation and weaning of kidney replacement therapy in acute kidney injury

The occurrence of acute kidney injury (AKI) in critically ill patients is often associated with increased morbidity and mortality rates. Despite extensive research, a consensus is yet to be arrived, especially regarding the optimal timing and indications for initiation of kidney replacement therapy (KRT) for critically ill patients. There is no clear guidance available on the timing of weaning from KRT. More recently, various biomarkers have produced promising prognostic prediction in such patients, regarding the need for KRT and its termination. Most of these biomarkers are indicative of kidney damage and stress, rather than recovery. However, large-scale validation studies are required to guide the cutoff values of these biomarkers among different patient cohorts so as to identify the optimum timing for KRT. This article reviews the kidney biomarkers in detail and summarizes the individual roles of biomarkers in the decision-making process for initiation and termination of the KRT among critically ill AKI patients and the supportive literature.

Distinct phenotyping of critical patients with demand-capacity imbalance initiating acute renal replacement therapy by consensus clustering

BACKGROUND

Certain patient subpopulations requiring dialysis initiation show varied survival rates and chances of ending renal replacement therapy (RRT). Consensus clustering can help identify these subgroups and their dialysis outcomes.

METHODS

The study included patients who were over 18 years old with urine output above 400 ml per day and an estimated glomerular filtration rate over 15 ml/min/1.73 m2. They underwent acute RRT because of systemic demand-capacity imbalance. Using consensus clustering with 33 clinical variables and urea:creatinine ratio (UCR) to the variables to investigate the catabolic demand. Endpoints were all-cause mortality and being dialysis-free at 180-day follow-up after RRT initiation.

RESULTS

Of 946 patients (mean 63 ± 17 years and 649 men, 68.6 %) three distinct phenotypes were identified. 509 (53.8%) patients died and 364 (38.5%) patients were weaned off dialysis. Cluster 2 showed better survival (60.23% vs. 53.18% [cluster 1] vs. 45.85% [cluster 3], P < 0.01) and higher possibility to be weaned off RRT (45.24% vs. 38.44% [cluster 1] vs. 31.62% [cluster 3], P < 0.01). High UCR had increased mortality (59.16% vs. 47.75%, P < 0.01) and a lower weaning rates (33.27%; 45.72%, P < .01). UCR with the clustering phenotype improved risk stratification.

CONCLUSIONS

Among critical patients undergoing RRT due to systemic demand-capacity imbalance, more than half of the patients died. We identified distinct phenotypes in demand-capacity imbalance in a heterogeneous cohort of patients initializing RRT. Additionally, we found that pre-dialysis UCR as a novel predictor for mortality and the likelihood of being dialysis-free.

Ensemble Machine Learning for Predicting 90-Day Outcomes and Analyzing Risk Factors in Acute Kidney Injury Requiring Dialysis

Purpose

Our objectives were to (1) employ ensemble machine learning algorithms utilizing real-world clinical data to predict 90-day prognosis, including dialysis dependence and mortality, following the first hospitalized dialysis and (2) identify the significant factors associated with overall outcomes.

Patients and Methods

We identified hospitalized patients with Acute kidney injury requiring dialysis (AKI-D) from a dataset of the Taipei Medical University Clinical Research Database (TMUCRD) from January 2008 to December 2020. The extracted data comprise demographics, comorbidities, medications, and laboratory parameters. Ensemble machine learning models were developed utilizing real-world clinical data through the Google Cloud Platform.

Results

The Study Analyzed 1080 Patients in the Dialysis-Dependent Module, Out of Which 616 Received Regular Dialysis After 90 Days. Our Ensemble Model, Consisting of 25 Feedforward Neural Network Models, Demonstrated the Best Performance with an Auroc of 0.846. We Identified the Baseline Creatinine Value, Assessed at Least 90 Days Before the Initial Dialysis, as the Most Crucial Factor. We selected 2358 patients, 984 of whom were deceased after 90 days, for the survival module. The ensemble model, comprising 15 feedforward neural network models and 10 gradient-boosted decision tree models, achieved superior performance with an AUROC of 0.865. The pre-dialysis creatinine value, tested within 90 days prior to the initial dialysis, was identified as the most significant factor.

Conclusion

Ensemble machine learning models outperform logistic regression models in predicting outcomes of AKI-D, compared to existing literature. Our study, which includes a large sample size from three different hospitals, supports the significance of the creatinine value tested before the first hospitalized dialysis in determining overall prognosis. Healthcare providers could benefit from utilizing our validated prediction model to improve clinical decision-making and enhance patient care for the high-risk population.

Recovery Dynamics and Prognosis After Dialysis for Acute Kidney Injury

Importance

The interplay among baseline kidney function, severity of acute kidney disease (AKD), and post-AKD kidney function has significant associations with patient outcomes. However, a comprehensive understanding of how these factors are collectively associated with mortality, major adverse cardiac events (MACEs), and end-stage kidney disease (ESKD) in patients with dialysis-requiring acute kidney injury (AKI-D) is yet to be fully explored.

Objective

To investigate the associations of baseline kidney function, AKD severity, and post-AKD kidney function with mortality, MACEs, and ESKD in patients with AKI-D.

Design, Setting, and Participants

This nationwide, population-based cohort study of patients with AKI-D was conducted between January 1, 2015, and December 31, 2018, using data from various health care settings included in the Taiwan nationwide population-based cohort database. Data analysis was conducted from April 28, 2022, to June 30, 2023.

Exposure

Exposure to severe AKI and baseline and post-AKD kidney function.

Main Outcomes and Measures

The primary outcomes were all-cause mortality and incident MACEs, and secondary outcomes were risks of permanent dialysis and readmission.

Results

A total of 6703 of 22 232 patients (mean [SD] age, 68.0 [14.7] years; 3846 [57.4%] male) with AKI-D with post-AKD kidney function follow-up and AKD stage data were enrolled. During a mean (SD) 1.2 (0.9) years of follow-up, the all-cause mortality rate was 28.3% (n = 1899), while the incidence rates of MACEs and ESKD were 11.1% (n = 746) and 16.7% (n = 1119), respectively. After adjusting for known covariates, both post-AKD kidney function and baseline kidney function, but not AKD severity, were independently associated with all-cause mortality, MACEs, ESKD, and readmission. Moreover, worse post-AKD kidney function correlated with progressive and significant increases in the risk of adverse outcomes.

Conclusions and Relevance

In this cohort study of patients with AKI-D, more than one-quarter of patients died after 1.2 years of follow-up. Baseline and post-AKD kidney functions serve as important factors associated with the long-term prognosis of patients with AKI-D. Therefore, concerted efforts to understand the transition from post-AKD to chronic kidney disease are crucial.

Circulating Fibroblast Growth Factor-23 Levels Can Predict Rapid Kidney Function Decline in a Healthy Population: A Community-Based Study

BACKGROUND

Fibroblast growth factor-23 (FGF-23) associates with decreased kidney function in patients with chronic kidney disease (CKD). However, the correlation between circulating FGF-23 levels and the rate of renal function decline in healthy individuals is largely unknown. We aimed to evaluate the predictive performance of FGF-23 for rapid kidney function decline (RKFD) in a community-based study.

METHODS

A total of 2963 people residing in northern Taiwan were enrolled from August 2013 to May 2018 for an annual assessment of kidney function for five years. The baseline estimated glomerular filtration rates (eGFR) were calculated using the 2009 and 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, which aggregates the values of serum creatinine and cystatin C (eGFRcr-cys). The outcome was RKFD-a 15% decrease in estimated glomerular filtration rate (eGFR) within the first four years, and a reduction in eGFR without improvement in the 5th year. A generalized additive model (GAM) was used to determine the cut-off value of FGF-23 to predict RKFD.

RESULTS

The incidence of RKFD was 18.0% (114/634). After matching for age and sex at a 1:1 ratio, a total of 220 subjects were analyzed. eGFRcr-cys was negatively correlated with total vitamin D level but seemed irrelevant to FGF-23. Multivariable logistic regression analysis showed that FGF-23, eGFRcr-cys, and urine albumin-to-creatinine ratio (UACR) were independent predictors of the possibility of RKFD. FGF-23 showed the best predictive performance for RKFD (AUROC: 0.803), followed by baseline eGFRcr-cys (AUROC: 0.639) and UACR (AUROC: 0.591). From the GAM, 32 pg/mL was the most appropriate cut-off value of FGF-23 with which to predict RKFD. The subgroup and sensitivity analyses showed consistent results that high-FGF-23 subjects had higher risks of RKFD.

CONCLUSIONS

Circulating FGF-23 level could be a helpful predictor for RKFD in this community-based population.

Research progress of fibroblast growth factor 23 in acute kidney injury

Fibroblast growth factor 23 (FGF23) is primarily produced in bones and mainly regulates calcium and phosphorus metabolism. The level of circulating FGF23 increases rapidly in the early stage of acute kidney injury (AKI). Recent studies have shown that FGF23 may serve as a biomarker for the diagnosis and poor prognosis of AKI. The mechanism of increased FGF23 in AKI may include increased production of FGF23, decreased renal clearance of FGF23, and some new regulatory factors, such as inflammation and glycerol 3-phosphate. However, the biological effects of elevated FGF23 in AKI are still unclear. It is also not known whether reducing the level of circulating FGF23 could alleviate AKI or its poor prognosis. Here, we review the pathophysiological mechanism and possible regulation of FGF23 in AKI and discuss the possibility of using FGF23 as a therapeutic target.

Distinct Subtyping of Successful Weaning from Acute Kidney Injury Requiring Renal Replacement Therapy by Consensus Clustering in Critically Ill Patients

Background: Clinical decisions regarding the appropriate timing of weaning off renal replacement therapy (RRT) in critically ill patients are complex and multifactorial. The aim of the current study was to identify which critical patients with acute kidney injury (AKI) may be more likely to be successfully weaned off RRT using consensus cluster analysis. Methods: In this study, critically ill patients who received RRT at three multicenter referral hospitals at several timepoints from August 2016 to July 2018 were enrolled. An unsupervised consensus clustering algorithm was used to identify distinct phenotypes. The outcomes of interest were the ability to wean off RTT and 90-day mortality. Results: A total of 124 patients with AKI requiring RRT (AKI-RRT) were enrolled. The 90-day mortality rate was 30.7% (38/124), and 49.2% (61/124) of the patients were successfully weaned off RRT for over 90 days. The consensus clustering algorithm identified three clusters from a total of 45 features. The three clusters had distinct features and could be separated according to the combination of urinary neutrophil gelatinase-associated lipocalin to creatinine ratio (uNGAL/Cr), Sequential Organ Failure Assessment (SOFA) score, and estimated glomerular filtration rate at the time of weaning off RRT. uNGAL/Cr (hazard ratio [HR] 2.43, 95% confidence interval [CI]: 1.36–4.33) and clustering phenotype (cluster 1 vs. 3, HR 2.7, 95% CI: 1.11–6.57; cluster 2 vs. 3, HR 44.5, 95% CI: 11.92–166.39) could predict 90-day mortality or re-dialysis. Conclusions: Almost half of the critical patients with AKI-RRT could wean off dialysis for over 90 days. Urinary NGAL/Cr and distinct clustering phenotypes could predict 90-day mortality or re-dialysis.

Neutrophil-to-lymphocyte ratio is a marker for acute kidney injury progression and mortality in critically ill populations: a population-based, multi-institutional study

Backgrounds

Neutrophil-to-lymphocyte ratio (NLR), a surrogate marker of systemic response to physiological stress, is used for prognosis prediction in many diseases. However, the usefulness of this marker for predicting acute kidney injury (AKI) progression is unclear.

Methods

This retrospective study was based on the Chang Gung Research Database. Patients admitted to the intensive care unit with a diagnosis of stage 1 or 2 AKI were identified. The primary outcome was a composite of progression to stage 3 AKI, requirement of renal replacement therapy, or 14-day in-hospital mortality. The association between NLR and the primary outcome was examined using a logistic regression model and multivariable analysis. The nonlinearity and cutoff points of this relationship were determined using a restricted cubic spline model.

Results

A total of 10,441 patients were enrolled. NLR level at the time of stage 1–2 AKI diagnosis was a marker of adverse outcomes. After adjustment for confounders, NLR was independently associated with the composite outcome of AKI progression, renal replacement therapy, or mortality. The restricted cubic spline model revealed a J-shaped curve, with the lowest odds ratio for an NLR between 7 and 38. Subgroup analysis revealed linear and J-shaped relationships between NLR and the primary outcome in patients admitted to the intensive care unit for medical reasons and for cardiovascular surgery, respectively.

Conclusions

NLR is an independent marker of AKI progression and in-hospital mortality. Because it is readily available in daily practice, it might be used for risk stratification in the AKI population.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01162-3.

GDF-15 Predicts In-Hospital Mortality of Critically Ill Patients with Acute Kidney Injury Requiring Continuous Renal Replacement Therapy: A Multicenter Prospective Study

Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine. This study evaluated the association between GDF-15 and in-hospital mortality among patients with severe acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT). Among the multicenter prospective CRRT cohort between 2017 and 2019, 66 patients whose blood sample was available were analyzed. Patients were divided into three groups according to the GDF-15 concentrations. The median GDF-15 level was 7865.5 pg/mL (496.9 pg/mL in the healthy control patients). Baseline characteristics were not different among tertile groups except the severity scores and serum lactate level, which were higher in the third tertile. After adjusting for confounding factors, the patients with higher GDF-15 had significantly increased risk of mortality (second tertile: adjusted hazards ratio [aHR], 3.67; 95% confidence interval [CI], 1.05-12.76; p = 0.041; third tertile: aHR, 6.81; 95% CI, 1.98-23.44; p = 0.002). Furthermore, GDF-15 predicted in-hospital mortality (area under the curve, 0.710; 95% CI, 0.585-0.815) better than APACHE II and SOFA scores. Serum GDF-15 concentration was elevated in AKI patients requiring CRRT, higher in more severe patients. GDF-15 is a better independent predictor for in-hospital mortality of critically ill AKI patients than the traditional risk scoring system such as APACHE II and SOFA scores.

Risk of new-onset autoimmune diseases in primary aldosteronism: a nation-wide population-based study

OBJECTIVE

The association between hyperaldosteronism and autoimmune disorders has been postulated. However, long-term incidence of a variety of new-onset autoimmune diseases (NOAD) among patients with primary aldosteronism has not been well investigated.

METHODS

From Taiwan's National Health Insurance Research Database with a 23-million population insurance registry, the identification of primary aldosteronism, essential hypertension and NOAD as well as all-cause mortality were ascertained by a validated algorithm.

RESULTS

From 1997 to 2009, 2319 primary aldosteronism patients without previously autoimmune disease were identified and propensity score-matched with 9276 patients with essential hypertension. Among those primary aldosteronism patients, 806 patients with aldosterone-producing adenomas (APA) were identified and matched with 3224 essential hypertension controls. NOAD incidence is augmented in primary aldosteronism patients compared with its matched essential hypertension (hazard ratio 3.82, P < 0.001, versus essential hypertension). Furthermore, NOAD incidence is also higher in APA patients compared with its matched essential hypertension (hazard ratio = 2.96, P < 0.001, versus essential hypertension). However, after a mean 8.9 years of follow-up, primary aldosteronism patients who underwent adrenalectomy (hazard ratio = 3.10, P < 0.001, versus essential hypertension) and took mineralocorticoid receptor antagonist (MRA) still had increased NOAD incidence (hazard ratio = 4.04, P < 0.001, versus essential hypertension).

CONCLUSION

Primary aldosteronism patients had an augmented risk for a variety of incident NOAD and all-cause of mortality, compared with matched essential hypertension controls. Notably, the risk of incident NOAD remained increased in patients treated by adrenalectomy or MRA compared with matched essential hypertension controls. This observation supports the theory of primary aldosteronism being associated with a higher risk of multiple autoimmune diseases.

Serum fibroblast growth factor 23 for early detection of acute kidney injury in critical illness

BACKGROUND

Serum fibroblast growth factor 23 (FGF23) is associated with acute kidney injury (AKI) and mortality in patients with critical illnesses. However, the accurate predictive performance of FGF23 on AKI remains inconclusive.

METHODS

Meta-analysis was performed using data sources including PubMed, Web of Science, EMBASE, and Cochrane (until June 1, 2021). Cohort or observational studies including patients with AKI and serum FGF23 level as the index test were included. The primary outcome was the AKI detective accuracy. This study has been registered in PROSPERO (CRD42021249930).

RESULTS

Eleven studies with 1946 patients in seven countries were included. Across all settings, the sensitivity and specificity for serum FGF23 levels to predict AKI were 82% (95% CI, 66-91%) and 77% (95% CI, 67-85%), respectively. The diagnostic odds ratio of FGF23 was 15.51 (95% CI, 4.89-49.19), with the pooled positive likelihood ratio of 3.62 (95% CI, 2.25-5.83) and a negative likelihood ratio of 0.23 (95% CI, 0.11-0.50). The area under the receiver operating characteristic curve to detect AKI was 0.86 (95% CI, 0.82-0.88). C-terminal FGF23 had a better performance than intact FGF23.

CONCLUSIONS

Plasma FGF23 is a valuable biomarker for incident AKI in critically ill patients. Comparisons of FGF23 with other biomarkers in AKI still need more studies to prove.

High plasma C-terminal FGF-23 levels predict poor outcomes in patients with chronic kidney disease superimposed with acute kidney injury

Background:

Elevated plasma C-terminal fibroblast growth factor-23 (cFGF-23) levels are associated with higher mortality in patients with chronic kidney disease (CKD) and acute kidney injury (AKI). Our study explored the outcome forecasting accuracy of cFGF-23 in critically ill patients with CKD superimposed with AKI (ACKD).

Methods:

Urine and plasma biomarkers from 149 CKD patients superimposed with AKI before dialysis were checked in this multicenter prospective observational cohort study. Endpoints were 90-day mortality and 90 days free from dialysis after hospital discharge. Associations with study endpoints were assessed using hierarchical clustering analysis, the generalized additive model, the Cox proportional hazard model, competing risk analysis, and discrimination evaluation.

Results:

Over a median follow up of 40 days, 67 (45.0%) patients died before the 90th day after hospital discharge and 39 (26.2%) progressed to kidney failure with replacement therapy (KFRT). Hierarchical clustering analysis demonstrated that cFGF-23 levels had better predictive ability for 90-day mortality than did other biomarkers. Higher serum cFGF-23 levels were independently associated with greater risk for 90-day mortality [hazard ratio (HR): 2.5; 95% confidence interval (CI) 1.5–4.1; p < 0.001]. Moreover, adding plasma cFGF-23 to the Demirjian AKI risk score model substantially improved risk prediction for 90-day mortality than the Demirjian model alone (integrated discrimination improvement: 0.06; p < 0.05; 95% CI 0.02–0.10). The low plasma cFGF-23 group was predicted having more weaning from dialysis in surviving patients (HR = 0.53, 95% CI, 0.29–0.95, p = 0.05).

Conclusions:

In patients with ACKD, plasma cFGF-23 levels are an independent risk factor to forecast 90-day mortality and 90-day progression to KFRT. In combination with the clinical risk score, plasma cFGF-23 levels could substantially improve mortality risk prediction.

Association between regional economic status and renal recovery of dialysis-requiring acute kidney injury among critically ill patients

The association between regional economic status and the probability of renal recovery among patients with dialysis-requiring AKI (AKI-D) is unknown. The nationwide prospective multicenter study enrolled critically ill adult patients with AKI-D in four sampled months (October 2014, along with January, April, and July 2015) in Taiwan. The regional economic status was defined by annual disposable income per capita (ADIPC) of the cities the hospitals located. Among the 1,322 enrolled patients (67.1 ± 15.5 years, 36.2% female), 833 patients (63.1%) died, and 306 (23.1%) experienced renal recovery within 90 days following discharge. We categorized all patients into high (n = 992) and low economic status groups (n = 330) by the best cut-point of ADIPC determined by the generalized additive model plot. By using the Fine and Gray competing risk regression model with mortality as a competing risk factor, we found that the independent association between regional economic status and renal recovery persisted from model 1 (no adjustment), model 2 (adjustment to basic variables), to model 3 (adjustment to basic and clinical variables; subdistribution hazard ratio, 1.422; 95% confidence interval, 1.022–1.977; p = 0.037). In conclusion, high regional economic status was an independent factor for renal recovery among critically ill patients with AKI-D.

Diagnostics, Risk Factors, Treatment and Outcomes of Acute Kidney Injury in a New Paradigm

Acute kidney injury (AKI) is a common clinical condition among patients admitted in the hospitals. The condition is associated with both increased short-term and long-term mortality. With the development of a standardized definition for AKI and the acknowledgment of the impact of AKI on patient outcomes, there has been increased recognition of AKI. Two advances from past decades, the usage of computer decision support and the discovery of AKI biomarkers, have the ability to advance the diagnostic method to and further management of AKI. The increasingly widespread use of electronic health records across hospitals has substantially increased the amount of data available to investigators and has shown promise in advancing AKI research. In addition, progress in the finding and validation of different forms of biomarkers of AKI within diversified clinical environments and has provided information and insight on testing, etiology and further prognosis of AKI, leading to future of precision and personalized approach to AKI management. In this this article, we discussed the changing paradigms in AKI: from mechanisms to diagnostics, risk factors, and management of AKI.

Serum N-terminal Pro-B-type Natriuretic Peptide Predicts Mortality in Cardiac Surgery Patients Receiving Renal Replacement Therapy

Background: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a useful cardiac biomarker that is associated with acute kidney injury (AKI) and mortality after cardiac surgery. However, its prognostic value in cardiac surgical patients receiving renal replacement therapy (RRT) remains unclear. Objectives: Our study aimed to assess the prognostic value of NT-proBNP in patients with established AKI receiving RRT after cardiac surgery. Methods: A total of 163 cardiac surgical patients with AKI requiring RRT were enrolled in this study. Baseline characteristics, hemodynamic variables at RRT initiation, and NT-proBNP level before surgery, at RRT initiation, and on the first day after RRT were collected. The primary outcome was 28-day mortality after RRT initiation. Results: Serum NT-proBNP levels in non-survivors was markedly higher than survivors before surgery (median: 4,096 [IQR, 962.0-9583.8] vs. 1,339 [IQR, 446-5,173] pg/mL; P < 0.01), at RRT initiation (median: 10,366 [IQR, 5,668-20,646] vs. 3,779 [IQR, 1,799-11,256] pg/mL; P < 0.001), and on the first day after RRT (median: 9,055.0 [IQR, 4,392-24,348] vs. 5,255 [IQR, 2,134-9,175] pg/mL; P < 0.001). The area under the receiver operating characteristic curve of NT-proBNP before surgery, at RRT initiation, and on the first day after RRT for predicting 28-day mortality was 0.64 (95% CI, 0.55-0.73), 0.71 (95% CI, 0.63-0.79), and 0.68 (95% CI, 0.60-0.76), respectively. Consistently, Cox regression revealed that NT-proBNP levels before surgery (HR: 1.27, 95% CI, 1.06-1.52), at RRT initiation (HR: 1.11, 95% CI, 1.06-1.17), and on the first day after RRT (HR: 1.17, 95% CI, 1.11-1.23) were independently associated with 28-day mortality. Conclusions: Serum NT-proBNP was an independent predictor of 28-day mortality in cardiac surgical patients with AKI requiring RRT. The prognostic role of NT-proBNP needs to be confirmed in the future.

Acute Kidney Injury and In-Hospital Mortality: A Retrospective Analysis of a Nationwide Administrative Database of Elderly Subjects in Italy

Background: The aim of this study was to investigate the association between acute kidney injury (AKI) and in-hospital mortality (IHM) in a large nationwide cohort of elderly subjects in Italy. Methods: We analyzed the hospitalization data of all patients aged ≥65 years, who were discharged with a diagnosis of AKI, which was identified by the presence of the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), and extracted from the Italian Health Ministry database (January 2000 to December 2015). Data regarding age, gender, dialysis treatment, and comorbidity, including the development of sepsis, were also collected. Results: We evaluated 760,664 hospitalizations, the mean age was 80.5 ± 7.8 years, males represented 52.2% of the population, and 9% underwent dialysis treatment. IHM was 27.7% (210,661 admissions): Deceased patients were more likely to be older, undergoing dialysis treatment, and to be sicker than the survivors. The population was classified on the basis of tertiles of comorbidity score (the first group 7.48 ± 1.99, the second 13.67 ± 2,04, and third 22.12 ± 4.13). IHM was higher in the third tertile, whilst dialysis-dependent AKI was highest in the first. Dialysis-dependent AKI was associated with an odds ratios (OR) of 2.721; 95% confidence interval (CI) 2.676–2.766; p < 0.001, development of sepsis was associated with an OR of 1.990; 95% CI 1.948–2.033; p < 0.001, the second tertile of comorbidity was associated with an OR of 1.750; 95% CI 1.726–1.774; p < 0.001, and the third tertile of comorbidity was associated with an OR of 2.522; 95% CI 2.486–2.559; p < 0.001. Conclusions: In elderly subjects with AKI discharge codes, IHM is a frequent complication affecting more than a quarter of the investigated population. The increasing burden of comorbidity, dialysis-dependent AKI, and sepsis are the major risk factors.

Meta-Analysis: Urinary Calprotectin for Discrimination of Intrinsic and Prerenal Acute Kidney Injury

Background: Urinary calprotectin is a novel biomarker that distinguishes between intrinsic or prerenal acute kidney injury (AKI) in different studies. However, these studies were based on different populations and different AKI criteria. We evaluated the diagnostic accuracy of urinary calprotectin and compared its diagnostic performance in different AKI criteria and study populations. Method: In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched PubMed, Embase, and the Cochrane database up to September 2018. The diagnostic performance of urinary calprotectin (sensitivity, specificity, predictive ratio, and cutoff point) was extracted and evaluated. Result: This study included six studies with a total of 502 patients. The pooled sensitivity and specificity were 0.90 and 0.93, respectively. The pooled positive likelihood ratio (LR) was 15.15, and the negative LR was 0.11. The symmetric summary receiver operating characteristic (symmetric SROC) with pooled diagnostic accuracy was 0.9667. The relative diagnostic odds ratio (RDOC) of the adult to pediatric population and RDOCs of different acute kidney injury criteria showed no significant difference in their diagnostic accuracy. Conclusion: Urinary calprotectin is a good diagnostic tool for the discrimination of intrinsic and prerenal AKI under careful inspection after exclusion of urinary tract infection and urogenital malignancies. Its performance is not affected by different AKI criteria and adult or pediatric populations.