Black and White Adults With CKD Hospitalized With Acute Kidney Injury: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

RATIONALE & OBJECTIVE

Few studies have investigated racial disparities in acute kidney injury (AKI), in contrast to the extensive literature on racial differences in the risk of kidney failure. We sought to study potential differences in risk in the setting of chronic kidney disease (CKD).

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

We studied 2,720 self-identified Black or White participants with CKD enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study from July 1, 2013, to December 31, 2017.

EXPOSURE

Self-reported race (Black vs White).

OUTCOME

Hospitalized AKI (≥50% increase from nadir to peak serum creatinine).

ANALYTICAL APPROACH

Cox regression models adjusting for demographics (age and sex), prehospitalization clinical risk factors (diabetes, blood pressure, cardiovascular disease, estimated glomerular filtration rate, proteinuria, receipt of angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers), and socioeconomic status (insurance status and education level). In a subset of participants with genotype data, we adjusted for apolipoprotein L1 gene (APOL1) high-risk status and sickle cell trait.

RESULTS

Black participants (n = 1,266) were younger but had a higher burden of prehospitalization clinical risk factors. The incidence rate of first AKI hospitalization among Black participants was 6.3 (95% CI, 5.5-7.2) per 100 person-years versus 5.3 (95% CI, 4.6-6.1) per 100 person-years among White participants. In an unadjusted Cox regression model, Black participants were at a modestly increased risk of incident AKI (HR, 1.22 [95% CI, 1.01-1.48]) compared with White participants. However, this risk was attenuated and no longer significant after adjusting for prehospitalization clinical risk factors (adjusted HR, 1.02 [95% CI, 0.83-1.25]). There were only 11 AKI hospitalizations among individuals with high-risk APOL1 risk status and 14 AKI hospitalizations among individuals with sickle cell trait.

LIMITATIONS

Participants were limited to research volunteers and potentially not fully representative of all CKD patients.

CONCLUSIONS

In this multicenter prospective cohort of CKD patients, racial disparities in AKI incidence were modest and were explained by differences in prehospitalization clinical risk factors.

Association Between Deceased Donor Acute Kidney Injury Assessed Using Baseline Serum Creatinine Back-Estimation and Graft Survival: Results From the French National CRISTAL Registry

RATIONALE & OBJECTIVE

Deceased donor acute kidney injury (AKI) frequently leads to kidney discards, but its impact on long-term graft survival in kidney transplant recipients remains unclear. We investigated the association between deceased donor AKI assessed using back-estimation of baseline serum creatinine (Scr) and graft survival.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Adult patients represented within the French CRISTAL registry who received a single kidney allograft from brain-dead deceased donors between January 2006 and December 2017.

EXPOSURE

A back-estimated Scr baseline value was derived for an assumed glomerular filtration rate at 75mL/min/1.73m², using the MDRD Study equation. A refined classification system for donor AKI was implemented as follows: no AKI, undetermined AKI/chronic kidney disease (CKD), recovery from AKI, and ongoing AKI.

OUTCOME

Death-censored graft survival.

ANALYTICAL APPROACH

Multivariable Cox models using a robust variance estimator for paired kidneys from the same donor.

RESULTS

We classified 26,786 recipients as follows: no AKI (n=19,276); undetermined AKI/CKD (n=1,745); recovery from AKI (n=2,392); and ongoing AKI (n=3,373). We observed 4,458 kidney graft losses during a median follow-up period of 5.7 years. Compared with no AKI, ongoing AKI was associated with an increased risk of graft failure (hazard ratio [HR], 1.24 [95% CI, 1.13-1.35]). The HRs for graft failure in the undetermined AKI/CKD and recovery from AKI groups (1.22 [95% CI, 1.07-1.38] and 1.18 [95% CI, 1.06-1.31], respectively) were similar to those observed in the ongoing AKI group. The adverse effect of deceased donor AKI was no longer evident when relying either on the admission or the lowest Scr throughout the procurement procedure as baseline Scr.

LIMITATIONS

No measurement of urine output in donors.

CONCLUSIONS

Deceased donor ongoing AKI, undetermined AKI/CKD, and recovery from AKI according to back-estimated baseline Scr are associated with decreased graft survival. The definition of baseline Scr as the first value measured on admission would have led to a misclassification bias and erroneous estimates.

Capmatinib-Induced Pseudo-Acute Kidney Injury: A Case Report

We present a case of pseudo-acute kidney injury (AKI) following capmatinib therapy in an 84-year-old man with combined non-small cell (adenocarcinoma) and small cell lung cancer with MET exon 14-skipping mutation. His past medical history was significant for chronic kidney disease stage 3 with a baseline serum creatinine (Scr) of 1.6mg/dL rising to 2.44mg/dL (estimated glomerular filtration rate [GFR] 24mL/min/1.73m²) while on capmatinib. Scr improved to 1.84mg/dL with the cessation of capmatinib but rose again to 2.22mg/dL upon resumption of therapy. Further investigation with cystatin C and renal iothalamate clearance showed that despite fluctuation in Scr levels, there was not much variation in GFR calculated using these methods. Urinalysis and urinary protein-creatinine ratio were unremarkable. Treatment with capmatinib was continued at reduced dose and a third instance of rise in Scr was observed, followed by a spontaneous return to baseline. Thus, MET inhibitor therapy can result in an asymptomatic rise in Scr, and it must be distinguished from AKI with more accurate non-creatinine-based methods to evaluate GFR. This could spare such patients from invasive diagnostic tests, such as a kidney biopsy, and premature cessation of prognostically important cancer therapies.

Real-Time Prediction of Acute Kidney Injury in Hospitalized Adults: Implementation and Proof of Concept

RATIONALE & OBJECTIVE

Acute kidney injury (AKI) is diagnosed based on changes in serum creatinine concentration, a late marker of this syndrome. Algorithms that predict elevated risk for AKI are of great interest, but no studies have incorporated such an algorithm into the electronic health record to assist with clinical care. We describe the experience of implementing such an algorithm.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

2,856 hospitalized adults in a single urban tertiary-care hospital with an algorithm-predicted risk for AKI in the next 24 hours>15%. Alerts were also used to target a convenience sample of 100 patients for measurement of 16 urine and 6 blood biomarkers.

EXPOSURE

Clinical characteristics at the time of pre-AKI alert.

OUTCOME

AKI within 24 hours of pre-AKI alert (AKI₂₄).

ANALYTICAL APPROACH

Descriptive statistics and univariable associations.

RESULTS

At enrollment, mean predicted probability of AKI₂₄ was 19.1%; 18.9% of patients went on to develop AKI₂₄. Outcomes were generally poor among this population, with 29% inpatient mortality among those who developed AKI₂₄ and 14% among those who did not (P<0.001). Systolic blood pressure<100mm Hg (28% of patients with AKI₂₄ vs 18% without), heart rate>100 beats/min (32% of patients with AKI₂₄ vs 24% without), and oxygen saturation<92% (15% of patients with AKI₂₄ vs 6% without) were all more common among those who developed AKI₂₄. Of all biomarkers measured, only hyaline casts on urine microscopy (72% of patients with AKI₂₄ vs 25% without) and fractional excretion of urea nitrogen (20% [IQR, 12%-36%] among patients with AKI₂₄ vs 34% [IQR, 25%-44%] without) differed between those who did and did not develop AKI₂₄.

LIMITATIONS

Single-center study, reliance on serum creatinine level for AKI diagnosis, small number of patients undergoing biomarker evaluation.

CONCLUSIONS

A real-time AKI risk model was successfully integrated into the EHR.

Peripheral Artery Disease: Its Adverse Consequences With and Without CKD

RATIONALE & OBJECTIVES

Chronic kidney disease (CKD) is a potent risk factor for macrovascular disease and death. Peripheral artery disease (PAD) is more common in patients with CKD and is associated with lower-limb complications and mortality. We sought to compare the prevalence of PAD in and outside the setting of kidney disease and examine how PAD affects the risk for adverse health outcomes, specifically lower-limb complications, cardiovascular events, and survival.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

453,573 adult residents of Manitoba with at least 1 serum creatinine measurement between 2007 and 2014.

EXPOSURE

PAD defined by hospital discharge diagnosis codes and medical claims.

OUTCOMES

All-cause mortality, cardiovascular events, and lower-limb complications, including foot ulcers and nontraumatic amputations.

ANALYTICAL APPROACH

Survival analysis using Cox proportional hazards models.

RESULTS

The prevalence of PAD in our study population was 4.5%, and patients with PAD were older, were more likely to be male, and had a higher burden of comorbid conditions, including diabetes and CKD. PAD was associated with higher risks for all-cause mortality, cardiovascular events, and lower-limb complications in patients with estimated glomerular filtration rate (eGFR) ≥ 60mL/min/1.73m², those with CKD GFR categories 3 to 5 (G3-G5), and those treated by dialysis (CKD G5D). Although HRs for PAD were lower in the CKD population, event rates were higher as compared with those with eGFR≥60mL/min/1.73m². In particular, compared with patients with eGFR≥60mL/min/1.73m² and without PAD, patients with CKD G5D had 10- and 12-fold higher risks for lower-limb complications, respectively (adjusted HRs of 10.36 [95% CI, 8.83-12.16] and 12.02 [95% CI, 9.58-15.08] for those without and with PAD, respectively), and an event rate of 75/1,000 patient-years.

LIMITATIONS

Potential undercounting of PAD and complications using administrative codes and the limited ability to examine quality-of-care indicators for PAD.

CONCLUSIONS

PAD is more common in patients with CKD G3-G5 and G5D compared with those with eGFR≥60mL/min/1.73m² and frequently leads to lower-limb complications. Medical interventions and care pathways specifically designed to slow or prevent the development of lower-limb complications in this population are urgently needed.

Performance of Serum Creatinine and Kidney Injury Biomarkers for Diagnosing Histologic Acute Tubular Injury

BACKGROUND

The diagnosis of acute kidney injury (AKI), which is currently defined as an increase in serum creatinine (Scr) concentration, provides little information on the condition's actual cause. To improve phenotyping of AKI, many urinary biomarkers of tubular injury are being investigated. Because AKI cases are not frequently biopsied, the diagnostic accuracy of concentrations of Scr and urinary biomarkers for histologic acute tubular injury is unknown.

STUDY DESIGN

Cross-sectional analysis from multicenter prospective cohort.

SETTINGS & PARTICIPANTS

Hospitalized deceased kidney donors on whom kidney biopsies were performed at the time of organ procurement for histologic evaluation.

PREDICTORS

(1) AKI diagnosed by change in Scr concentration during donor hospitalization and (2) concentrations of urinary biomarkers (neutrophil gelatinase-associated lipocalin [NGAL], liver-type fatty acid-binding protein [L-FABP], interleukin 18 [IL-18], and kidney injury molecule 1 [KIM-1]) measured at organ procurement.

OUTCOME

Histologic acute tubular injury.

RESULTS

Of 581 donors, 98 (17%) had mild acute tubular injury and 57 (10%) had severe acute tubular injury. Overall, Scr-based AKI had poor diagnostic performance for identifying histologic acute tubular injury and 49% of donors with severe acute tubular injury did not have AKI. The area under the receiver operating characteristic curve (AUROC) of change in Scr concentration for diagnosing severe acute tubular injury was 0.58 (95% CI, 0.49-0.67) and for any acute tubular injury was 0.52 (95% CI, 0.45-0.58). Compared with Scr concentration, NGAL concentration demonstrated higher AUROC for diagnosing both severe acute tubular injury (0.67; 95% CI, 0.60-0.74; P=0.03) and any acute tubular injury (0.60; 95% CI, 0.55-0.66; P=0.005). In donors who did not have Scr-based AKI, NGAL concentrations were higher with increasing severities of acute tubular injury (subclinical AKI). However, compared with Scr concentration, AUROCs for acute tubular injury diagnosis were not significantly higher for urinary L-FABP, IL-18, or KIM-1.

LIMITATIONS

The spectrum of AKI cause in deceased donors may be different from that of a general hospitalized population.

CONCLUSIONS

Concentrations of Scr and kidney injury biomarkers (L-FABP, IL-18, and KIM-1) lack accuracy for diagnosing acute tubular injury in hospitalized deceased donors. Although urinary NGAL concentration had slightly higher discrimination for acute tubular injury than did Scr concentration, its overall AUROC was still modest.