First Tool to Specifically Assess Fatigue in Dialysis Is Validated

The first instrument developed to assess fatigue specifically among patients undergoing hemodialysis for kidney failure appears to be reliable and consistent at quantifying the endpoint, a longitudinal cohort study shows.

Fatigue affects most patients with kidney failure who receive hemodialysis, contributes to poor quality of life, and is associated with higher risks of cardiovascular disease, depression, and early death. Unfortunately, fatigue can be difficult to quantify.

Implementing the three-question Standardized Outcomes in Nephrology-Hemodialysis (SONG-HD) instrument in all trials involving patients on hemodialysis will enable consistent assessment of fatigue in a way that is meaningful for patients, the investigators say.

The research was published online October 22 in the Clinical Journal of the American Society of Nephrology (ASN).

"Fatigue is a critically important outcome for patients receiving hemodialysis," writes lead author Angela Ju, PhD, University of Sydney, New South Wales, Australia.

"Establishing a core outcome measure for fatigue will allow researchers to do two important things: to quickly and accurately assess the impact a new intervention has on fatigue as experienced by patients receiving hemodialysis, and to allow the comparison of interventions across different trials to see which one is superior in terms of its effect on fatigue," Ju said in a press release from ASN.

Patients Asked to Score Three Aspects of Fatigue

The study assessed the SONG-HD Fatigue instrument in accordance with the US Food and Drug Administration guidelines for patient-reported outcome measures (PROM).

A total of 485 patients from Australia, the United Kingdom, and Romania participated in the study. Most patients were 51 to 70 years of age, 60% were men, and close to 80% were White.

Most participants had been on hemodialysis for up to 5 years. Each participant completed the SONG-HD Fatigue measure and a visual analog scale (VAS) at three time points: baseline, 1 week, and 12 days. Participants were also asked to complete the 12-item Short-Form survey (SF-12) or the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) at baseline.

The SONG-HD Fatigue instrument asks patients to rate their experience of three aspects of fatigue previously identified as important to patients when researchers were developing the PROM on a Likert scale of 0 to 3.

SONG-HD Fatigue Instrument

In the past week	Not at all	A little	Quite a bit	Severely
Did you feel tired?
Did you lack energy?
Did fatigue limit your usual activities?

The SONG-HD Fatigue instrument had good internal consistency. Mean scores varied among UK patients compared with those in Australia, at a mean difference of 0.93 (P = .004), and Romania, at a mean difference of 1.39 (P < .001).

In contrast, there were no differences in mean scores on the SONG-HD Fatigue measure between patients in Australia and Romania.

"There was a high correlation between the FACIT-F and SONG-HD Fatigue total scores for all three countries," the investigators report. The instrument also had significant correlation with VAS scores for fatigue and the SF-12.

Newer to Hemodiaylsis, Higher SONG-HD Scores

Patients who had been on hemodialysis for less than a year had higher SONG-HD Fatigue scores than those who had been on it for more than a year (P = .004).

Similarly, scores were significantly higher for patients on dialysis for less than a year compared to those on dialysis for 1 to 5 years (P = .03), but not those on dialysis for over 6 years. There were no significant differences in this regard between groups by country.

Not unexpectedly, scores on the SONG-HD Fatigue measure were similar between baseline assessments and those done at the later time points, because patients reported overall fatigue at each of three time points and not fluctuations in fatigue over time, the authors write.

Study Limitations

In an accompanying editorial, Sarah Ramer, MD, Weill Cornell Medical College, and Jennifer Scherer, MD, NYU School of Medicine, New York City, point out that although the study examined two key measurement properties of the SONG-HD Fatigue scale, reliability and validity, it did not examine the third, responsiveness, namely, an ability to detect clinically meaningful change.

The investigators attribute this limitation to uncertainty about when exactly a clinically meaningful change in fatigue might occur and the lack of an intervention expected to change fatigue.

Another limitation relevant to US researchers, according to the editorialists, is that the race and ethnicity of participants (very few Black or Latin American patients) does not reflect the US maintenance hemodialysis population.

And given that mean scores observed on the SONG-HD Fatigue scale did, in fact, differ significantly by country, "it is possible that within a country, mean scores could significantly differ by racial or ethnic background of the respondents," they write.

But even if one group rates their fatigue as better or worse than another, "the scale can still be reliable and valid in both groups."

The bigger question is whether researchers will use the new PROM. "At this time, trials including fatigue as a core outcome are still scarce," Ramer and Scherer point out.

Given the multifactorial nature of fatigue in patients on dialysis, it's possible that only a multifactorial intervention will be able to address it, they suggest. And while they recognize that "many barriers to developing and testing such an intervention still exist...the lack of a validated PROM is no longer one of them."

Ramer and Scherer recommend that physicians simply ask their patients on dialysis if they are experiencing fatigue and whether they want to do something about it.

"In some cases, treating fatigue might entail trade-offs, such as spending more time on dialysis," they acknowledge.

Patient Perspective: New Tool Doesn't Capture Post-Dialysis Fatigue

In an accompanying patient perspective, Henning Sondergaard, a psychologist with the Danish Kidney Association, who himself has late-stage kidney disease, points out that the new PROM was not designed to capture post-dialysis fatigue, which for many patients is the most debilitating part of their treatment and can last from a few minutes to more than 12 hours.

Sondergaard also noted more frequent dialysis is a worthwhile trade-off for many people because they have more energy and a better quality of life in their off-treatment time.

"Perhaps the problem with fatigue in hemodialysis is amplified by the way in which hemodialysis is currently administered," he writes.

None of the other authors have reported any relevant financial relationships.

CJASN. Published online October 22, 2020. Full text, Editorial, Patient perspective

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