This article has Open Peer Review reports available.
Protocol of a randomized controlled trial of an erythropoietin stimulating agent decision aid for anemia treatment in kidney disease
- Lauren B. Beach†1, 2,
- Marcus Wild†1, 2,
- Gowri Ramachandran3,
- H. Omer Ikizler4 and
- Kerri L. Cavanaugh1, 2Email authorView ORCID ID profile
© The Author(s). 2016
Received: 11 February 2016
Accepted: 1 July 2016
Published: 18 July 2016
Erythropoiesis-stimulating agents (ESAs) are commonly used for the treatment of anemia due to chronic kidney disease (CKD) and end stage renal disease (ESRD). Patients often lack an understanding of the potential risks and benefits of ESAs, despite government mandated education on this topic. Decision aids are tools commonly used to discuss important information in health care settings. To address this knowledge gap, we designed this study to evaluate the effectiveness of a novel ESA decision aid at promoting informed shared decision making (ISDM) between patients and providers related to ESA use for CKD- and ESRD-related anemia.
Using the principles of informed shared decision making theory, we designed and piloted an ESA decision aid intended to increase CKD and ESRD patient understanding of the potential risks and benefits of ESAs. Informed by the findings during development, the ESA decision aid was modified and finalized for testing. We will perform a randomized clinical trial to assess if administration of the ESA decision aid improves patient understanding of the risks and benefits of ESA use compared to control patients receiving standard care. Participants with either CKD or ESRD and who are receiving ESAs will be eligible for participation. The primary outcome is patients’ score on the Patient Anemia Knowledge in Kidney Disease (PAKKD) survey assessed at enrollment and 3 months after. Secondary outcomes include decisional conflict related to ESAs, and patient satisfaction with provider communication.
The Anemia Risk Communication for patients with Kidney Disease (ARC-KD) study will assess the effectiveness of a novel ESA decision aid to improve patient understanding of ESA use to manage CKD- and ESRD-related anemia. This decision aid is the first resource targeted to improve patient understanding of anemia management in the kidney health context. With the increasing options available for anemia management, this will serve as an important foundation to evolve in the future to optimize anemia-related shared decision making.
ClinicalTrials.gov, number NCT01992926. Registered 11/14/2013.
KeywordsShared decision making Decision aid IPDAS Anemia Chronic kidney disease Erythropoietin stimulating agent Dialysis Patient provider communication End stage renal disease
Anemia affects nearly 95 % of patients receiving dialysis and 15 % of those with chronic kidney disease (CKD) . Erythropoiesis-stimulating agents (ESAs) have been used for the past two decades to treat the complications of anemia in patients with kidney disease. The inability of ESAs to improve patient-reported outcomes, such as fatigue, in clinical trials has cast doubt on the potential benefits of ESAs relative to their risks, which include a near doubling of risk for stroke . In March 2010, the Food and Drug Administration (FDA) required the administration of medication guides to patients receiving ESAs to improve their understanding of the potential risks and benefits of ESA treatment . Unfortunately, these basic tools may not adequately educate patients thoroughly about the risks and benefits of ESA therapy. Even patients with kidney disease who frequently visit their nephrologists have knowledge deficits about their disease and the role of the kidney in anemia . This is likely in part because communication is difficult from both the patient and the physician perspectives, and this is amplified when discussing possible risks .
Informed shared decision making (ISDM) has emerged as a leading evidence- based theory that, when applied successfully, can improve patient-provider communications surrounding health risks . Best-practice ISDM requires the provider to initiate conversations by introducing the concept of patient choice, describe the options of care available to patients, often by employing a decision aid, and help patients better define their preferences to make good health care decisions . The Ottawa Decision Support Framework, an evidence-based set of guidelines used in the development and evaluation of over 30 empirically derived decision aids, also requires that the ISDM process be critically evaluated for quality and its impact on health outcomes [8, 9]. Decision aids developed by systematically applying ISDM theory can help to reinforce consistent application of ISDM principles during the health care decision making process .
In this study, we sought to develop and evaluate a decision aid for ESA therapy to be administered to ESRD and CKD patient populations. We hypothesized that the use of an ESA decision aid that follows the International Patient Decision Aid Standards (IPDAS)  and adheres to expert opinion for optimizing communication with low health literacy and numeracy patients  will increase patient knowledge of anemia in kidney disease, reduce patient uncertainty related to ESA use, and increase overall patient care satisfaction. We also hypothesize that these effects might be enhanced for vulnerable patient populations, who stand to benefit from these improvements the most [12, 13].
Methods and study design
Study design summary
Phase 1a: development of the ESA decision aid
To prepare for Phase I implementation, we conducted a literature review to support the development of the ESA decision aid. We focused our search on papers that described theories of ISDM in medical practice using the Ottawa Decision Support Framework. We also reviewed examples of high quality decision aids in the Decision Aid Library Inventory (DALI) available online via the Ottawa Hospital Research Institute . This search revealed limited research and resources describing kidney-specific decision aids and none describing anemia management decision aids, kidney health related or otherwise . Importantly, however, we did find evidence that the application of ISDM principles to patient-provider communications can improve health knowledge and outcomes in CKD and ESRD patient populations, including in patient sub-populations with low health literacy and numeracy .
This search led us to consider the IPDAS quality domains as guiding principles when developing the ESA decision aid . These domains define high quality decision aids as those that  [involve a] systematic development process  provide information about options  present probabilities  clarify and express values  use patient stories  guide or coach [patients and providers] in deliberation and communication  disclose conflicts of interest  deliver patient aids on the internet  balance presentation of options  use plain language  base information on up to date scientific evidence and  establish effectiveness . The minimum quality domains and standards necessary to certify high-quality, ISDM-informed decision aids under the IPDAS framework are still undergoing consideration and are not yet defined .
The IPDAS domains not addressed by the draft decision aid were “5. using patient stories”, “7. disclosing conflicts of interest” and “8. delivering patient aids on the internet.” We chose not to include an individual patient story due to concerns that variability in the degree individual patients related to the patient in the story could bias patient decision-aid assisted decision-making results [11, 16]. Though the aid does not state it, no conflict of interest exists for any person who developed the decision aid. Lastly, because our trial planned to deliver the decision aid in person for research purposes, it was not made available online.
To further evaluate the quality of the draft ESA decision aid, we engaged patients and providers to review the usefulness and accessibility of the tool, in accordance with recent decision aid best practices . A convenience sample of 18 nephrology medical providers and 39 patients with kidney disease at Vanderbilt University Medical Center provided feedback on the draft ESA decision aid. Patients providing feedback had a CKD or ESRD diagnosis, were at least 18 years of age, were receiving ESAs for anemia, spoke English, and had no significant visual impairment. No compensation was given to participants.
Patients and providers independently reviewed printed copies of the ESA decision aid and completed a 17-question survey to provide feedback about the design and usefulness of the ESA decision aid at promoting informed shared decision making. Results from the surveys were compiled and used to revise the ESA decision aid.
Phase 1b: revision of the ESA decision aid
Additionally, both patients and providers expressed confusion about the use of smile face icons in Section 4 (pictorial representation of stroke risk due to ESA use) to represent symbolically the probability of adverse events due to ESA use. Patients reported these symbols were a poor choice to symbolize risk, because they associated smile faces with positive rather than with adverse health outcomes. In response, the revised ESA decision aid included solid dots in the pictograph (Fig. 3).
Phase 1c: usability testing of the ESA decision aid
After revision, the ESA decision aid was evaluated for usability with the Suitability Assessment of Materials (SAM) survey . SAM scores of 70–100 are superior, scores of 40–69 are adequate, while scores less than 40 are inadequate. Previous evaluation of 69 kidney disease patient education materials found a mean overall usability score of 58 % . The ESA decision aid SAM score for the revised ESA decision aid was 89 %, demonstrating a superior mean SAM usability score. The next phase of this study will test this version of the decision aid informed by both provider and patient stakeholders.
Phase 2: randomized controlled trial evaluating the use of an ESA decision aid to improve patient anemia knowledge
Study outcomes, measures, and patient characteristics
Outcomes, Measures & Characteristics
Data Source by Outcome
Timeline and Frequency
Patient Anemia Knowledge in Kidney Disease (PAKKD) 
Provider Communication Satisfaction
Satisfaction with Provider Communications (CAT) 
Health Decision Certainty
Decisional Conflict Scale (DCS) 
Perceived Communication Efficacy
Perceived Efficacy in Patient-Physician Interactions (PEPPI) 
Patient Demographic Information
Patient Numeracy Assessments
Schwartz Risk Numeracy Test 
Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) 
Patient Electronic Medical Record Hemoglobin Lab Values
Following informed consent, ARC-KD study participants will complete the indicated survey metrics during at least one of three possible time points: enrollment (Baseline Pre-Visit), up to one week after the baseline enrollment visit (Post-Visit) and three months after enrollment (Three Months). Study staff will obtain hemoglobin lab values from each participant’s electronic health care record at baseline and three months.
Target population and eligibility criteria
Planned recruitment criteria for study participants include diagnosis of CKD or ESRD, current ESA therapy, age between 18 and 80, and English fluency. Patients will be excluded if they have significant cognitive impairment or visual impairment. Cognitive impairment will be determined by asking patients to complete the Mental Status Assessment of Older Adults, or Mini-Cog . Participants will be excluded if they do not speak English, due to a lack of available staff to translate.
Recruitment of participants
Participants will be recruited from the in-center and home dialysis clinics at Vanderbilt University Medical Center, as well as the outpatient nephrology clinic at the Vanderbilt Clinic. Potential participants will be identified by an examination of their electronic medical record. Patients will be actively recruited by a study coordinator who will approach eligible individuals, explain the content of the study, and answer any questions the individual may have. Written informed consent will be obtained from all participants. Reminder phone calls and appointment cards are given to patients at all clinics participating in the study to increase patient appointment attendance. These methods will also be used to increase retention of study participants, who will receive the intervention or control usual care during a pre-scheduled patient appointment.
Using blind and secure allocation, participants will be randomly assigned to one of two intervention arms: 1.) the usual care control group, or 2.) the ESA decision aid intervention group. Randomization will not be blocked by site, due to recruitment from within one large nephrology practice. The allocation sequence will be computer-generated. Participants will be recruited and assigned to intervention groups by the study coordinator, who will be blind to the allocation sequence. After assignment trial participants and care providers not involved in the study will not be blinded to the assignment.
Usual care group
Participants who are randomly assigned to the control group will receive standard care from their existing nephrologists, nurses, and clinical staff. As all of the participants in the study will be receiving ESA therapy, this care may include a description of the purpose of the medication by the staff member administering the injection and counseling about its purpose and potential risks, but without use of the ESA decision aid.
Participants randomly assigned to the intervention group will receive a paper copy of the ESA decision aid (Fig. 3). This decision aid will be administered by and discussed with a nephrology nurse practitioner, who will explain the purpose and function of ESA’s, the goal hemoglobin levels for those receiving ESAs, the positive and negative effects of the medication, and additional resources available to patients. In order to maintain consistency across the clinics, the same nurse practitioner will administer the decision aid tool to all intervention participants across the dialysis clinics. Similarly, a nurse in the CKD clinic that is assigned to anemia management will be responsible for administering the ESA decision aid. Each of these clinical personnel will be trained and oriented to the content and recommended use of the decision aid.
Data collection, follow-Up, and outcomes
All participants will be assessed using in-person questionnaires at baseline before or after their study visit and at 3 months after enrollment, as described in Table 1. Changes in patient scores that occur between baseline pre-visit and after the administration of the ESA decision aid will be compiled and analyzed. Additionally, all patients’ medical records will be abstracted for relevant comorbidities, lab values, medications, and vital signs at both baseline and 3 month study visits. In this minimal risk study monitoring for any reported associated adverse events such as anxiety with the educational intervention will be performed throughout its duration by the PI and study team. All available efforts will be made to blind outcome survey assessors from group assignment.
Data management, privacy and monitoring
Data will be entered into a secure online database by the study coordinator. To protect patient confidentiality, study-specific identification numbers will be used in the study database in lieu of participant identifying information. Only the PI and the study coordinator will have access to the study identification/patient identification link log, which will be destroyed after study completion. The PI will monitor data quality and data queries will be resolved by the study coordinator. Due to the low risk profile of the study, ARC-KD will not convene a data monitoring committee.
The randomly assigned intervention or control group will be the primary independent variable for intention to treat analysis. Multiple imputations will be used to handle missing data. Evaluation of the primary outcome of patient anemia knowledge will be determined by comparing intervention and control group Patient Anemia Knowledge in Kidney Disease (PAKKD)  survey scores between baseline pre-visit and post-visit as well as baseline pre-visit and 3 months post-intervention for both study arms. Evaluation of the secondary analyses of provider communication satisfaction, health decisional certainty and perceived self-efficacy in patient-provider communications and patient kidney care will be similarly measured and analyzed using the Communication Assessment Tool (CAT) , Decisional Conflict Scale (DCS)  and Perceived Efficacy in Patient-Physician Interactions (PEPPI)  surveys, respectively. Baseline pre-visit variables will be compared between the study arms to assess the successfulness of randomization including gender, age, education and race, using median and interquartile ranges for continuous variables and frequencies and proportion for categorical variables to ensure homogeneity. Chi-squared tests for categorical variables and Wilcoxon-rank sum test for continuous variables will be used to assess the differences in baseline data between intervention and control. We will use linear regression models to compare the change in the PAKKD anemia knowledge scores from baseline to post-visit and baseline to 3 months post intervention between the study arms. Baseline pre-visit values of the outcome variable will be included as a model covariate in linear regression analysis to compare changes from baseline pre-visit. Lastly, planned exploratory analyses include performing logistic regression analysis to assess association between the likelihood of achieving or maintaining hemoglobin targets.
Sample size and power
We are aware of no other previous studies examining the effectiveness of a shared decision-making intervention designed for the use of ESAs in CKD or ESRD. Based upon previous experience of using a brief educational worksheet to improve general kidney knowledge , we estimate a possible doubling or tripling improvement in the odds of improved kidney health knowledge. For the primary outcome of the PAKKD anemia knowledge score (range: 0–100 %), preliminary data have showed a mean (standard deviation) improvement of 59 % (20 %) . Using a t-test for independent samples, the calculated minimum detectable difference is 11 % (59 % in control, 70 % in intervention), showing 19 % relative improvement in anemia knowledge score with 80 % power at a 2-sided significance level. For the purposes of this study, the proposed sample size of 100 participants should be adequate and informative.
It has been acknowledged from multiple levels of care and governance that communication of risk and proper use for ESAs in the treatment of anemia in CKD and ESRD is an area of concern that must be addressed . We designed the Anemia Risk Communication for patients with Kidney Disease (ARC-KD) trial to create and evaluate the effectiveness of a novel ESA decision aid to assist CKD and ESRD patients and providers in deciding whether or not to use ESAs to manage anemia related to underlying kidney disease. Well-designed decision aids have been shown in randomized controlled trials to improve health knowledge, lower decisional conflict, and promote accurate risk perceptions for patients living with a variety of complex health conditions . Decision aids well-designed to address barriers to ISDM for vulnerable patient populations, such as patients with limited health literacy, have been shown to improve patient knowledge. In diabetics, such aids have even been implicated in achieving tighter glycemic control . After study completion we will make the decision aid available via the internet for review by the public and use by health professionals.
Our study will make advances in a clinically important, but understudied, area of kidney disease care. It will also allow us to assess whether this ESA decision aid is associated with higher patient knowledge of anemia, as well as their satisfaction and certainty regarding their decision to use ESAs. By using the ISDM approach to improving patient understanding of the risks associated with ESA use in CKD, we hope to mitigate barriers to effective patient-provider communication such as low health literacy, and develop a resource for providers to use cooperatively with their patients. Patient feedback on the utility of the revised ESA decision aid indicated kidney disease patients who have only recently started receiving anemia treatment may receive the maximum benefit from the implementation of the decision aid tool. Interestingly, patient feedback also suggested the tool could be useful in explaining the impact of anemia to family members. Importantly, as the pharmacologic options for treatment of anemia in kidney disease expand in the future, a kidney-specific anemia therapy decision aid may become a required component of optimized patient-centered care.
ARC-KD, the anemia risk communication for patients with kidney disease study; CAT, communication assessment tool; CKD, chronic kidney disease; DALI, decision aid library inventory; DCS, decisional conflict scale; ESA, erythropoiesis-stimulating agents; ESRD, end stage renal disease; FDA, food and drug administration; IPDAS, international patient decision aid standards; ISDM, informed shared decision making; PAKKD, patient anemia knowledge in kidney disease; PEPPI, perceived efficacy in patient-physician interactions
This research was supported by NIH R03DK93852, R01DK103935 (Cavanaugh) and P30DK079341-05S1. Dr. Beach is supported by T32DK007569. REDCap services were supported by UL1 TR000445 from NCATS/NIH. Its contents are solely the responsibility of the authors and do not necessarily represent official views of the National Institutes of Health.
Availability of data and materials
Not applicable at this stage.
KC conceived, designed, and conducted the study and contributed to the draft of the manuscript. LBB contributed to the conception and design of the study and drafted the manuscript. MW contributed to the design and conduct of the study and drafted the manuscript. GR contributed to the conception and design of the study and contributed to the draft of the manuscript. HOI contributed to the design and conduct of the study and to the draft of the manuscript. All authors approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Ethics approval and consent to participate
Institutional Review Board approval for this study was obtained from the Vanderbilt University Institutional Review Board, approval number 130784. All ongoing and planned research involving human subjects will be performed in accordance with the Declaration of Helsinki. All participants provided informed written or verbal consent for participation, including all patients and medical providers engaged in the development of the decision aid in Phase 1 of the study.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Collins AJ, Foley RN, Herzog C, Chavers B, Gilbertson D, Ishani A, et al. US renal data system 2012 annual data report. Am J Kidney Dis. 2013;61(1 Suppl 1):A7. e1-476.View ArticlePubMedGoogle Scholar
- Winkelmayer WC. Against TREATing all patients alike: lessons from an FDA advisory committee meeting. J Am Soc Nephrol. 2011;22(1):1–2.View ArticlePubMedGoogle Scholar
- Drug Safety Communication FDA. Erythropoiesis-stimulating agents (ESAs)-procrit, epogen and aranesp. 2010.Google Scholar
- Wright JA, Wallston KA, Elasy TA, Ikizler TA, Cavanaugh KL. Development and results of a kidney disease knowledge survey given to patients with CKD. Am J Kidney Dis. 2011;57(3):387–95.View ArticlePubMedGoogle Scholar
- Gigerenzer G, Gaissmaier W, Kurz-Milcke E, Schwartz LM, Woloshin S. Helping doctors and patients make sense of health statistics. Psychol Sci Public Interest. 2007;8(2):53–96.View ArticlePubMedGoogle Scholar
- Bot AG, Bossen JK, Herndon JH, Ruchelsman DE, Ring D, Vranceanu AM. Informed shared decision-making and patient satisfaction. Psychosomatics. 2014;55(6):586–94.View ArticlePubMedGoogle Scholar
- Brehaut JC, Carroll K, Elwyn G, Saginur R, Kimmelman J, Shojania K, et al. Informed consent documents do not encourage good-quality decision making. J Clin Epidemiol. 2012;65(7):708–24.View ArticlePubMedGoogle Scholar
- O’Connor AM, Jacobsen MJ, Stacey D. An evidence-based approach to managing women’s decisional conflict. J Obstet Gynecol Neonatal Nurs. 2002;31(5):570–81.View ArticlePubMedGoogle Scholar
- O’Connor AM, Tugwell P, Wells GA, Elmslie T, Jolly E, Hollingworth G, et al. A decision aid for women considering hormone therapy after menopause: decision support framework and evaluation. Patient Educ Couns. 1998;33(3):267–79.View ArticlePubMedGoogle Scholar
- Coulter A, Stilwell D, Kryworuchko J, Mullen PD, Ng CJ, van der Weijden T. A systematic development process for patient decision aids. BMC Med Inform Decis Mak. 2013;13 Suppl 2:S2.View ArticlePubMedPubMed CentralGoogle Scholar
- Elwyn G, O’Connor A, Stacey D, Volk R, Edwards A, Coulter A, et al. Developing a quality criteria framework for patient decision aids: online international Delphi consensus process. BMJ. 2006;333(7565):417.View ArticlePubMedPubMed CentralGoogle Scholar
- McCaffery KJ, Holmes-Rovner M, Smith SK, Rovner D, Nutbeam D, Clayman ML, et al. Addressing health literacy in patient decision aids. BMC Med Inform Decis Mak. 2013;13 Suppl 2:S10.View ArticlePubMedPubMed CentralGoogle Scholar
- Dageforde LA, Cavanaugh KL. Health literacy: emerging evidence and applications in kidney disease care. Adv Chronic Kidney Dis. 2013;20(4):311–9.View ArticlePubMedPubMed CentralGoogle Scholar
- Patient Decision Aids. Decision Aid Library Inventory (DALI) Ottawa Hospital Research Institute2015 [updated Last Updated June 22, 2015 August 28, 2015]. Available from: https://decisionaid.ohri.ca/cochinvent.php.
- Joseph-Williams N, Newcombe R, Politi M, Durand MA, Sivell S, Stacey D, et al. Toward minimum standards for certifying patient decision aids: a modified Delphi consensus process. Med Decis Making. 2013;34(6):699–710.View ArticlePubMedGoogle Scholar
- Ubel PA, Loewenstein G. The role of decision analysis in informed consent: choosing between intuition and systematicity. Soc Sci Med. 1997;44(5):647–56.View ArticlePubMedGoogle Scholar
- Tuot DS, Davis E, Velasquez A, Banerjee T, Powe NR. Assessment of printed patient-educational materials for chronic kidney disease. Am J Nephrol. 2013;38(3):184–94.View ArticlePubMedPubMed CentralGoogle Scholar
- Borson S, Scanlan J, Brush M, Vitaliano P, Dokmak A. The mini-cog: a cognitive ‘vital signs’ measure for dementia screening in multi-lingual elderly. Int J Geriatr Psychiatry. 2000;15(11):1021–7.View ArticlePubMedGoogle Scholar
- Cavanaugh KL, Sanghani SN, Wallston KA, Thamer M, Cotter DJ, Rothman R, Ikizler TA. Anemia knowledge is limited among patients with kidney disease receiving ESA therapy. J Am Soc Nephrol. 2010;21:643A.Google Scholar
- Makoul G, Krupat E, Chang CH. Measuring patient views of physician communication skills: development and testing of the communication assessment tool. Patient Educ Couns. 2007;67(3):333–42.View ArticlePubMedGoogle Scholar
- O’Connor AM. Validation of a decisional conflict scale. Med Decis Making. 1995;15(1):25–30.View ArticlePubMedGoogle Scholar
- Maly RC, Frank JC, Marshall GN, DiMatteo MR, Reuben DB. Perceived efficacy in patient-physician interactions (PEPPI): validation of an instrument in older persons. J Am Geriatr Soc. 1998;46(7):889–94.View ArticlePubMedGoogle Scholar
- Wright Nunes J, Greene JH, Wallston K, Eden S, Shintani A, Elasy T, et al. Pilot study of a physician-delivered education tool to increase patient knowledge about CKD. Am J Kidney Dis. 2013;62(1):23–32.View ArticlePubMedGoogle Scholar
- Manns BJ, Tonelli M. The new FDA labeling for ESA--implications for patients and providers. Clin J Am Soc Nephrol. 2012;7(2):348–53.View ArticlePubMedPubMed CentralGoogle Scholar
- O’Connor AM, Bennett CL, Stacey D, Barry M, Col NF, Eden KB, et al. Decision aids for people facing health treatment or screening decisions. Cochrane Database Syst Rev. 2009;3:CD001431.Google Scholar
- Cavanaugh K, Wallston KA, Gebretsadik T, Shintani A, Huizinga MM, Davis D, et al. Addressing literacy and numeracy to improve diabetes care: two randomized controlled trials. Diabetes Care. 2009;32(12):2149–55.View ArticlePubMedPubMed CentralGoogle Scholar
- Schwartz LM, Woloshin S, Black WC, Welch HG. The role of numeracy in understanding the benefit of screening mammography. Ann Intern Med. 1997;127(11):966–72.View ArticlePubMedGoogle Scholar
- Cella D, Yount S, Sorensen M, Chartash E, Sengupta N, Grober J. Validation of the functional assessment of chronic illness therapy fatigue scale relative to other instrumentation in patients with rheumatoid arthritis. J Rheumatol. 2005;32(5):811–9.PubMedGoogle Scholar