Author Interview: Michael G. Shlipak, MPH |
Publication:
Author Interview: Michael G. Shlipak, MPH
Presurgical Serum Cystatin C and Risk of Acute Kidney Injury After Cardiac Surgery.
Am J Kidney Dis. 2011 May 19.
Shlipak MG, Coca SG, Wang Z, Devarajan P, Koyner JL, Patel UD, Thiessen-Philbrook H, Garg AX, Parikh CR; TRIBE-AKI Consortium.
Department of Medicine, San Francisco VA Medical Center and University of California, San Francisco, San Francisco, San Francisco, CA; Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA. |
What are the main findings of the study? |
Our study compared the ability of pre-operative measures of kidney function – creatinine and cystatin C – with the incidence of acute kidney injury (AKI) during hospitalization following cardiac surgery. This multi-center cohort included 1,147 subjects enrolled in the TRIBE-AKI project. All had both creatinine and cystatin C measured prior to the hospitalization for surgery. We found that cystatin C had a much stronger and more linear association with AKI risk than either creatinine or creatinine-based estimated GFR (eGFR). AKI risk prediction was significantly improved by cystatin C above and beyond clinical risk factors and the creatinine measurement.
Cystatin C levels had the strongest independent association with AKI. In contrast, for creatinine level, the intermediate kidney function group had no significant independent association with AKI. Serum creatinine had a less severe risk gradient with AKI risk, while eGFR-Cr quintiles had the weakest association. Associations of kidney function with severe AKI were less linear across quintiles, but the worst quintile of kidney function had by far the highest risks.
The addition of cystatin C plus creatinine levels provided a moderate and significant incremental increase compared with smaller and nonsignificant changes with the addition of creatinine level alone or eGFR-Cr. Presurgical cystatin C was better than creatinine at predicting the risk of AKI after cardiac surgery.
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Were any of the findings unexpected? |
Yes, we expected the benefits to be larger than they were. For the severe AKI outcome, the C statistic was 0.73 for presurgical risk variables alone, and with the addition of either creatinine level or eGFR-Cr, increased to 0.77. Cystatin C level only marginally and nonsignificantly increased the C statistic to 0.78. Results for persistent severe AKI were similar. The findings were moderate, but future studies will need to be carried out with more diverse ethnic groups represented.
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What should clinicians and patients take away from this study? |
This is another example of cystatin C having stronger prognostic utility than creatinine levels. For “high-stakes” clinical situations like surgery or administration of medications toxic to the kidney, it may be worth adding a second measure of kidney function. Cystatin C is now widely available clinically and can be measured with automated analyzers, cheaply and efficiently. |
What recommendations do you have for nephrology health care providers as a result of your study? |
We believe that it is time to incorporate cystatin C into routine clinical practice. Pre-operative risk stratification is one possible indication. Another would be to validate the diagnosis of CKD in persons with eGFR<60ml/min/1.73m2 based on creatinine who are not known to have kidney disease or albuminuria. With confirmation from future studies, cystatin C levels may be a more accurate biomarker in predicting patients at risk for developing AKI post cardiac surgery. Clinicians can consider monitoring cystatin C levels in association with creatinine levels when they have a patient who is at higher risk for developing AKI postoperatively.
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| Abstract: |
BACKGROUND:
Acute kidney injury (AKI) after cardiac surgery is associated with poor outcomes, but is challenging to predict from information available before surgery.
STUDY DESIGN:
Prospective cohort study.
SETTING & PARTICIPANTS:
The TRIBE-AKI (Translational Research Investigating Biomarker Endpoints in Acute Kidney Injury) Consortium enrolled 1,147 adults undergoing cardiac surgery at 6 hospitals from 2007-2009; participants were selected for high AKI risk.
PREDICTORS:
Presurgical values for cystatin C, creatinine, and creatinine-based estimated glomerular filtration rate (eGFR) were categorized into quintiles and grouped as "best" (quintiles 1-2), "intermediate" (quintiles 3-4), and "worst" (quintile 5) kidney function.
OUTCOMES:
The primary outcome was AKI Network (AKIN) stage 1 or higher; ≥0.3 mg/dL or 50% increase in creatinine level.
MEASUREMENTS:
Analyses were adjusted for characteristics used clinically for presurgical risk stratification.
RESULTS:
Average age was 71 ± 10 years (mean ± standard deviation); serum creatinine, 1.1 ± 0.3 mg/dL; eGFR-Cr, 74 ± 9 mL/min/1.73 m(2); and cystatin C, 0.9 ± 0.3 mg/L. 407 (36%) participants developed AKI during hospitalization. Adjusted odds ratios for intermediate and worst kidney function by cystatin C were 1.9 (95% CI, 1.4-2.7) and 4.8 (95% CI, 2.9-7.7) compared with 1.2 (95% CI, 0.9-1.7) and 1.8 (95% CI, 1.2-2.6) for creatinine and 1.0 (95% CI, 0.7-1.4) and 1.7 (95% CI, 1.1-2.3) for eGFR-Cr categories, respectively. After adjustment for clinical predictors, the C statistic to predict AKI was 0.70 without kidney markers, 0.69 with creatinine, and 0.72 with cystatin C. Cystatin C also substantially improved AKI risk classification compared with creatinine, based on a net reclassification index of 0.21 (P < 0.001).
LIMITATIONS:
The ability of these kidney biomarkers to predict risk of dialysis-requiring AKI or death could not be assessed reliably in our study because of a small number of patients with either outcome.
CONCLUSIONS:
Presurgical cystatin C is better than creatinine or creatinine-based eGFR at forecasting the risk of AKI after cardiac surgery.
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Home Dialysis Summit Recommends Policy Changes to Increase Home Dialysis Usage
WASHINGTON, April 25, 2012 /PRNewswire -- On the heels of the first National Summit on Home Dialysis Policy, Summit organizers released a report reflecting the views of the delegates -- leaders in the kidney disease patient, clinician, facility and industry communities -- on federal policy steps to improve utilization of home dialysis for patients who can benefit from this often advantageous form of treatment. Many of the organizers also announced they have formed a new alliance, called the Alliance for Home Dialysis, to advance the recommendations identified at the Summit.
The Summit's "Report of the Delegates" highlights key findings from a March 29th meeting in Washington, DC where experts probed why, despite widely accepted and well-documented benefits of home dialysis -- improved outcomes, enhanced patient satisfaction, improved quality of life, and lower costs-- fewer than ten percent of the more than 390,000 current U.S. dialysis patients receive treatment at home. Current rates of home dialysis utilization reflect a steep decline from the 1970s, when almost 40% of U.S. dialysis patients were treated in-home.
Specifically, delegates found that policymakers should work with stakeholders in the dialysis community to confront three areas:
Accessibility: Patients and clinicians face array of hurdles in education, training, and infrastructure that hinder equalized access to home dialysis.
Accountability: Utilization of home dialysis can be improved through measures within government programs that are designed to recognize and support excellence in the delivery of home dialysis services.
Aligning Incentives: Reimbursement policies, regulation of new technologies and other policy incentives can be realigned to better support federal policy goals of expanding access to home dialysis.
The Report includes 15 recommendations to serve these goals, including that federal policymakers should:
Maintain parity for home and in-center dialysis in Medicare reimbursement;
Support home dialysis mentoring programs, particularly those that use existing patients as mentors; and
Align federal and state regulatory requirements for home therapies, such as revising the Centers for Medicare and Medicaid Services Conditions for Coverage requirements, to reflect differences in home and in-center dialysis.
Summit supporters will begin work through the new Alliance to dialogue with federal policymakers and advance policy improvements in the three consensus areas that emerged at the Summit.
SOURCE National Summit on Home Dialysis Policy
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National Kidney Foundation's Top 10 Things Every Dialysis Patient Should Know.
- You have treatment choices. Options exist for how, where and when you dialyze. Dialysis can be done in a hospital, in a dialysis unit that is not part of a hospital, or at home. You and your doctor will decide which place is best, based on your medical condition and your wishes. There are different types of dialysis - peritoneal and hemodialysis. Work with your health care team to determine a treatment plan that makes you feel comfortable. Recent studies show that the majority of patients beginning in-center hemodialysis (HD) know very little, if anything, about the option to dialyze at home. Once informed, 40% or more of patients are interested in this treatment option, and yet less than 10% actually begin home dialysis. If you're dissatisfied with the type of dialysis treatment that you're receiving, ask your healthcare team if another type of dialysis treatment would be better.
- You can compare in-center dialysis facilities online. Information on over 5,600 US-based dialysis centers is available online through the Medicare website. To help you make choices about your care, you can compare different facilities side-by-side and evaluate each facility based upon clinic characteristics and quality measures. You can search for dialysis facilities by name or geographic proximity. After completing an initial facility comparison to determine which facilities best meet your needs - such as the number of hemodialysis stations at a particular location and whether there are evening shifts available - visit the facilities that you're most interested in. Talk to the staff and other patients, as well as your doctor to ensure that this dialysis facility is a good fit for you.
- There are ways to prepare ahead for an emergency. Ask your dialysis facility about their emergency plan in case of a snow storm, fire, power outage or other natural disaster. As back up, make sure you have the names, locations and phone numbers of other dialysis units and hospitals in your area. Since regular community transportation services may not be working in an emergency, be prepared to make other arrangements for getting to dialysis. You may need to contact the police and Emergency Medical Services (EMS) for assistance. If you dialyze at home, make sure you have at least two weeks' worth of unexpired supplies on hand. If you have to miss a dialysis treatment, begin your emergency meal plan.
- There is an easy way to transfer patient records between clinics. There is an easy, secure way for your health care team to transfer your treatment records online. In 2009, the Centers for Medicare and Medicaid Services (CMS) created a centralized web-based data collection system called CROWNWeb to help reduce and eliminate patient treatment interruptions. This central system helps to streamline patient care regardless of the reason for changing dialysis centers. For example, if you've been admitted to the hospital, or if you needed to relocate during an emergency evacuation, your doctors and health care team can access up-to-date information about your dialysis so that you continue to receive appropriate care no matter where you are.
- You can travel while on dialysis.
Dialysis centers are located in every part of the United States and in many foreign countries. The treatment is standardized, but you need to plan ahead by making an appointment for dialysis at another center before you go. The staff at your center may help you make these appointments.
- You can be your own best advocate. Know what key questions to ask your doctor or other healthcare professionals. Take notes so that you can refer back to them later. Partner with your doctor and decide on a treatment plan together. Advocate for yourself and share how you're feeling.
- You have many rights. You as a patient have a great deal of control over your treatments. Patients have a bill of rights which includes receiving quality care, counseling about your medical information, and an expectation of privacy.
You also have responsibilities. Once you decide on a course of treatment, it's important to follow the recommendations of your health care team. If you decide to receive in-center dialysis, arrive at dialysis on time so that you can receive the full treatment without delays.
- You can receive insurance coverage. If you have end stage renal failure, you are likely eligible for Medicare insurance coverage. Speak with your health care team and social worker for help filling out insurance paperwork.
- You may need to follow a special diet. When your kidneys are not working properly, you may not be able to eat everything you like, and you may need to limit how much you drink. Your diet may vary according to the type of dialysis you receive. It is important to speak with a renal dietitian so that you are able to understand what you can and cannot eat based on your full health history.
- Dialysis patients can work. Many dialysis patients can go back to work or school after they have gotten used to dialysis. After establishing a dialysis routine, many patients have more energy and find that they are able to time to work around this new schedule. Some patients even find creative ways to work remotely from dialysis with the use of a laptop or cell phone, depending on their field of expertise.
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Help, I Need Dialysis!
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An internationally known nephrologist and life-long kidney patient educator explain how dialysis works, each of the ways to do it, and how your treatment choice may affect your diet, energy level, work, travel, sexuality and fertility, sleep, and survival. Comprehensive and fully referenced, this book is a must-read if you face the life-changing choices that come with kidney failure. |
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