Minutes to Recovery after a Hemodialysis Session: A Simple Health-Related Quality of Life Question That Is Reliable, Valid, and Sensitive to Change

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1 Minutes to Recovery after a Hemodialysis Session: A Simple Health-Related Quality of Life Question That Is Reliable, Valid, and Sensitive to Change Robert M. Lindsay,* Paul A. Heidenheim,* Gihad Nesrallah, Amit X. Garg,* and Rita Suri;* on behalf of the Daily Hemodialysis Study Group London Health Sciences Centre *Division of Nephrology and Optimal Dialysis Research Unit and Department of Epidemiology and Biostatistics, University of Western Ontario, London, Ontario, and Division of Nephrology, Humber River Regional Hospital, Toronto, Ontario, Canada Patients who have end-stage renal failure and are treated by hemodialysis (HD) face a stressful chronic illness with a demanding treatment regimen that affects quality of life. Quality-of-life domains can be measured by assessment questionnaires that are easy to complete, reliable, valid, and sensitive to change. There is current interest in HD regimens that provide more frequent treatments (e.g., daily) than the conventional thrice weekly. Improvement in quality of life by these regimens has been reported. A published prospective, cohort, controlled study (London Daily/Nocturnal Hemodialysis Study) included the results of a number of qualityof-life indicators that were applied to the study patients. In general, the indicators used were well established and of proven validity. Included was one single question that was added intuitively and had not received previous validation: How long does it take you to recover from a dialysis session? The responses to this question allow the validation of this simple question as a tool to be used in HD clinical research. Twenty-three patients who were treated by frequent HD (5 to 7 d or nights) and 22 control subjects who were treated by thrice-weekly dialysis were studied during an 18-mo period. The time to recovery question was administered along with a battery of renal disease specific questionnaires and the Generic Medical Outcomes Survey 36 Item Short Form (SF-36) plus the global Health Utilities Index. Missing data rates, reliability over time, construct validity, and sensitivity to change were assessed from the time to recovery responses by standard methods. The question was administered on a total of 314 occasions and answered successfully on 313. The test retest correlation over 3-mo intervals was highly significant (r 0.962, P 0.000; n 100). Convergent construct validity was established by significant correlations between time to recovery and fatigue (r 0.38, P 0.000; n 313), dialysis stress (r 0.348, P 0.000), disease stress (r 0.374, P 0.000), SF-36 subscales especially vitality (r P 0.000), and the Health Utilities Index (r 0.232, P 0.000). These scales captured mainly physical or physiologic domains. Divergent construct validity was established by lack of correlations between time to recovery and a number of subscales that captured mainly emotional or psychosocial domains, e.g., SF-36 subscale for role emotional (r 0.102, NS) and dialysis stressors such as access problems (r 0.015, NS) or equipment malfunction (r 0.032, NS). Test sensitivity was established when the conventionally dialyzed group showed no significant difference in time to recovery between baseline and other time periods, whereas the daily/nocturnal group had a significant reduction between baseline (while on conventional dialysis) and the result at each other time period (minimum P 0.05). There also was a significant difference between the control and experimental groups over time (ANOVA P 0.000). The response to the question, How long does it take you to recover from a dialysis session? is interpreted easily, is easy to which to respond, shows stability over time by test retest, shows both convergent and divergent validity, and is sensitive to change. As such, it should be considered as a standard question in HD-related studies in which a health-related quality-of-life outcome is examined. Clin J Am Soc Nephrol 1: , doi: /CJN Patients who have ESRD and are treated by hemodialysis (HD) face a stressful and disruptive chronic illness with a complex and demanding treatment regimen. This has an impact on the quality of life of both patients and Received January 4, Accepted May 4, Published online ahead of print. Publication date available at Address correspondence to: Dr. Robert Lindsay, London Health Sciences Centre, 800 Commissioners Road East, London, Ontario, Canada N6A 4G5. Phone: ; Fax: ; robert.lindsay@lhsc.on.ca their families, changing the distribution of responsibility with regard to decision making, employment, and housework as well as affecting diet, recreation, and social activity (1 3). Members of the nephrologic team therefore should be concerned not only with the biologic and physiologic but also with the psychologic and social functioning of their patients. Knowledge of the latter can aid in treatment decisions, improve patient compliance, and supplement morbidity and mortality measures in evaluative research. Consequently, there is the need for assessment tools that address the multidimensional nature of patient quality of life in clinical research settings. For such tools to be of Copyright 2006 by the American Society of Nephrology ISSN: /

2 Clin J Am Soc Nephrol 1: , 2006 Quality-of-Life Question Related to Recovery after HD 953 value, they must be reliable, valid, and sensitive to change over time and to the impact of alternative treatment interventions. Such assessment tools usually take the form of questionnaires. These should be straightforward, easy to understand, short, and easy to complete to maximize return rates and minimize missing data. There currently is interest in the provision of HD regimens that provide more frequent treatments (e.g., daily) than the conventional thrice-weekly treatment paradigm that has been used worldwide for the past 30 yr. A number of studies have demonstrated improvement in quality of life of HD patients shortly after changing from conventional to more frequent treatments (4 8). Reported benefits of daily HD include increased energy, strength, and endurance (5,9,10). The fatigue, uremic, symptoms, and dietary restrictions that normally compromise the quality of life of HD patients have been shown to decrease significantly after patients switched to short hours daily or slow nocturnal HD (stated by Kjellstrand to the Task Force on Daily Dialysis, sponsored by the National Institute of Diabetes and Digestive and Kidney Disease, Bethesda, MD, 2001). The London Daily/Nocturnal Study was an unblinded, prospective, cohort, controlled study that was designed to compare patients who underwent short-hours, high-efficiency daily HD or long, slow, overnight (nocturnal) HD, each performed 5 to 7 d/wk, and conventional thrice-weekly HD. The results of the study now have been reported fully in a supplement to the American Journal of Kidney Diseases (Am J Kidney Dis 42[Suppl 1]: S1 S70, 2003) and include the results of a number of qualityof-life indicators that were applied to the study patients (5). The instruments that were applied to this population included a number of generic or global quality-of-life scales that were composed of general questions with broad applicability together with disease-specific instruments that contained items that were tailored deliberately to particular diseases or conditions. In general, the instruments used were well established and of proven validity and had been used by the authors in a number of HD-related studies. Included in the battery of questionnaires that was given to the patients was one single question that was included intuitively and had not received previous validation. This question was a simple open-ended one asking the patient, How long does it take you to recover from a dialysis session? The responses that were given to this question have allowed us now to validate this simple question as a tool that could be used in HD research in which different HD treatment methods are to be compared. Materials and Methods Research Questions In patients who are being treated with both conventional and frequent HD and are asked a question to assess minutes to recovery after a treatment session: 1. What is the missing data rate? 2. What is the test retest reliability of the response? 3. How valid is the question with regard to the burden of the treatment? 4. How sensitive is the question to a change in treatment from conventional to frequent HD? Study Patients Patients were followed for 18 mo. The results of the study, including quality-of-life indicators, were reported previously (5). Eleven patients were treated by short-hours daily therapy; 12 patients were treated by nocturnal HD along with 22 control subjects who were matched by age, gender, comorbidity, and dialysis site (e.g., in-center full-care hospital HD versus home or minimal-assisted self-care HD or satellite full-care HD). Frequent HD patients all were treated at home. The control subjects were treated in-center, at a satellite dialysis unit, or in the home. The details of the study group demographics are given in Table 1; their treatment details are described elsewhere (11). Assessing HD Recovery Time The patients responses to the single open-ended question, How long does it take you to recover from a dialysis session? were converted to a number of minutes as follows: Answers given in minutes were recorded directly. Answers in hours were multiplied by 60. Variants of half a day, including the next day, were given a value of 720 min. Variants of one day were given a value of 1440 min. Variants of more than a day were given a value of 2160 min (36 h). Missing Data Rates The proportion of unanswered questions was expressed as a percentage of the number of times the question was asked. Other Measures of Quality of Life The study participants completed three sets of quality-of-life assessment tools: 1. A locally developed renal disease specific set of questionnaires that assessed dialysis symptoms, uremic (or disease) symptoms, psychosocial stress, and social-leisure activities. All of these questionnaires have been validated (12). To the questionnaire that assessed dialysis symptoms was added the intuitive question regarding the recovery time from the dialysis treatment. 2. The Generic Medical Outcomes Survey 36 Item Short Form (SF-36) (13,14). 3. The global Health Utilities Index (HUI) (15). Baseline measurements were obtained during the first week of the study while all patients remained on conventional HD therapy, and subsequent measurements were obtained every 3 mo through 18 mo of follow-up while patients were on their assigned daily/nocturnal or conventional HD therapy. All questionnaires were self-administered and were completed either during a dialysis treatment (control patients who were undergoing in-center or satellite HD; occasionally daily HD patients when dialyzed at time of a clinic visit) or at a study clinic visit (the rest, including all nocturnal HD patients). The question regarding minutes to recovery was directed to the last week of treatments. Analysis Reliability. Reliability is used to assess the extent to which an item, a scale, or an instrument will measure a domain and give the same results when administered to patients at different times or locations, when the administrations do not differ in the nature of the domain they are measuring. To assess the reliability of the HD recovery

3 954 Clinical Journal of the American Society of Nephrology Clin J Am Soc Nephrol 1: , 2006 Table 1. Demographics of study and control patients at study entry a Characteristic Daily HD b Nocturnal HD b Control c Gender (female:male) 4:7 3:10 8:14 Age (range mean SD ) 33 to 67 ( ) 38 to 56 ( ) 28 to 76 ( ) Source modality home HD self-care HD in-center HD satellite HD peritoneal dialysis Comorbidities diabetes hypertension heart disease hyperparathyroidism Vascular access AV fistula synthetic graft catheter a AV, arteriovenous; HD, hemodialysis. b One nocturnal HD patient subsequently transferred to daily HD after entering the study. c The final two study patients entered did not have matched control patients and were not included in the statistical analysis. question, we used test retest methods to quantify the linear correlation in patient response at any time point from 0 to 15 mo with the next retest adjacent follow-up response (i.e., 3 to 18 mo). This was carried out only on the control patients who were undergoing conventional intermittent HD. The response from the patients who were undergoing the experimental HD was to be used for the assessment of sensitivity to change (see below). Given that the question was a single item, other methods to assess reliability, including internal consistency and splithalves reliability, were not relevant. In addition, test retest reliability was assessed once for all patients by comparing the 6- with the 9-mo response. This period was chosen arbitrarily with the assumption that patients should be in a relatively steady state even if some (the experimental group) had changed from intermittent to more frequent HD treatments. No attempt to make corrections for times when a given patient may have had an intercurrent illness was made. Therefore, one cannot assume that the measured domain was a constant. Validity. Construct validity centers on the question as to whether the assessment tool actually measures the underlying theoretical concept, here a specific domain of quality of life. Generally, this is demonstrated by showing that the answers to the tool correlate in logical directions with other measured variables. To do this, the time to recovery (minutes) response was correlated with the other scale scores recorded by each patient at the same time, the question being included in the battery of quality-of-life questions given to each patient at repeated intervals. Convergent construct validity for time to recover (minutes) from HD as an indicator of dialysis treatment burden was established through a series of correlation analyses showing that it has statistically significant relationships with other variables that are known or assumed to be related to the burden of dialysis. Similarly, divergent construct validity of time to recover (minutes) from HD was established through a series of correlation analyses showing that it had no relationship with other variables that also are known or assumed to be unrelated to the burden of dialysis. The validity correlations were applied with all test results both from control subjects who were undergoing conventional intermittent HD and from experimental patients in the daily/nocturnal group. The correlation analyses used Pearson correlations, and two-tailed significance was established. Sensitivity to Change. The ability of a quality-of-life outcome to detect change over time is critical for its usefulness in clinical trials that assess the health benefits of dialysis. To assess sensitivity to change of the minutes to recovery question, we compared responses to the question in each patient in the experimental daily/nocturnal group before (i.e., while on conventional dialysis ) with the results that were obtained after the patient changed to the experimental quotidian form of dialysis. This was tested by paired t test that compared the baseline (on conventional dialysis) result with the result that was obtained at each time period. It also was examined by ANOVA of between-group comparisons Results Missing Data Rate The missing data rate was virtually 0%. The question regarding time to recover (minutes) from HD was administered on a total of 314 occasions and answered successfully on 313 of these. Test Retest Reliability The test retest correlation over 3-mo time intervals in the conventional control group was highly significant (r 0.962, P 0.000; n 100). The test retest correlation between the 6- and 9-mo response for all patients also was significant (r 0.954, P 0.000; n 36) Validity Convergent Construct Validity. The significant correlations between time to recovery (minutes) and Fatigue scores,

4 Clin J Am Soc Nephrol 1: , 2006 Quality-of-Life Question Related to Recovery after HD 955 Table 2. Convergent construct validity correlations between time to recovery (minutes) and other measures of quality of life (n 312/313) Quality-of-Life Measure Specific Variable Pearson Correlation Significance (Two-Tailed) Fatigue End of dialysis Between dialysis sessions Before dialysis Mean Dialysis stress Total Hypotension Tingling extremities Muscle cramps Itching Dizziness Nausea Chest pain Headache Shivering Vomiting Disease stress Total Aching arms/legs Difficulty concentrating Being weak and tired Restless legs Itchiness Muscle cramps BP problems Dizziness Up/down health Lack of appetite Nausea Shortness of breath Sleep problems Being permanently ill Weight gain Sexual performance problems Headaches Easily feel cold Fear of death/dying Psychosocial stress Total Interference with children Diet restrictions Friendship strain Seen/treated as sick person Fluid restrictions Dependence on others Vocational interference Less of a man/woman Loss of family role Interference with social activities Lack of personal freedom Interference with intimacy Altered body image Marriage strain

5 956 Clinical Journal of the American Society of Nephrology Clin J Am Soc Nephrol 1: , 2006 Table 2. Continued Quality-of-Life Measure Specific Variable Pearson Correlation Significance (Two-Tailed) Social/leisure activity Total Volunteer work Large social functions Letter writing Reading Individual sports Outdoor hobbies Team sports Regular exercise Clubs, unions, organizations Entertaining at home Shopping Movies, concerts, plays, etc TV, radio Telephone visiting SF-36 subscales b Vitality Physical components summary General health Bodily pain Physical functioning Social functioning Role physical Mental health Mental components summary HUI scale (Mark II) c HUI subscales Hearing level Pain level (Mark II) Pain level (Mark III) Mobility level Cognition level a HUI, Health Utilities Index; SF-36, Generic Medical Outcomes Survey 36 Item Short Form. b SF-36 subscales are calculated such that a higher score indicates better health or functioning. For example, a high score on the Bodily Pain subscale means less pain. c Higher HUI scores indicate better functioning; higher subscale scores indicate worse functioning, e.g., more pain, lower cognition. subscales of the Dialysis Stress questionnaire, subscales of the Disease Stress, Psychosocial Stress subscales, and with the subscales of the Social-Leisure Activity questionnaire are shown in Table 2. The significant correlations between time to recover (minutes) and the SF-36 subscales and the HUI scale and its subscales also are shown in Table 2. Divergent Construct Validity. The lack of correlations between time to recover (minutes) from HD and certain subscales are shown for Dialysis Stressors, Psychosocial Stress, Social-Leisure Activities, and HUI in Table 3. In addition, there was a nonsignificant negative correlation between time to recover (minutes) from HD and the SF-36 subscale for role emotional (r 0.102, P 0.073; n 313). Test Sensitivity The values for time to recover (minutes) from HD are shown for the control and the daily/nocturnal HD groups at baseline and at other follow-up periods in Table 4. The results here are expressed as mean SD. The same information is presented in Figure 1. The control (conventional dialysis) group showed no significant difference in time to recover (minutes) from HD between baseline and any other time period. In the experimental (daily/nocturnal) patient group, there is a significant difference between the baseline result and the result at each other time period (minimum P 0.05). There also was a significant difference between the control and experimental groups over time (ANOVA P 0.00). Discussion The responses to the single open-ended question, How long does it take you to recover from a dialysis session? indicate that the question is understood easily. In this study, the question was answered in all but one of 314 times. The majority of

6 Clin J Am Soc Nephrol 1: , 2006 Quality-of-Life Question Related to Recovery after HD 957 Table 3. Divergent construct validity correlations between time to recovery (minutes) and other measurements of quality of life (n 309/313) Quality of Life Measure Specific Variable Pearson Correlation Significance (Two-Tailed) Dialysis stressors Back pain Access problems Dialyzer/line problems Equipment malfunction Psychosocial stressors Financial problems Interference with vacations Social/leisure activity Church and related Small social functions Indoor hobbies Family get-togethers Get-togethers with friends Educational activities Bingo, cards, table games HUI subscales Vision level (Mark III) Speech level (Mark III) Emotion level (Mark III) Ambulation level (Mark III) Dexterity level (Mark III) Self-care level (Mark II) Emotion level (Mark II) Table 4. Time to recover (minutes) responses shown for daily/nocturnal HD patients and control HD patients at time 0 and at 3-mo intervals thereafter a Minutes to Recover from Dialysis 0 3 Mo 6 Mo 9 Mo 12 Mo 15 Mo 18 Mo Daily HD b b b b b b n Nocturnal b b b n Control b n a Data are mean SD. n varies because of open enrollment of the study and availability of collected data at a given time point. b P 0.05 versus baseline. the patients gave a direct answer in minutes or hours (297 of 313 times [95%]). The variants of half a day etc. occurred in only 5% (16 times). The responses to the question seemed stable with a high test retest correlation over a 3-mo time interval. There was strong evidence of convergent construct validity between time to recovery (minutes) and a number of other quality-of-life scales. There was a significant moderate positive association between time to recover (minutes) from HD and mean fatigue (r 0.38, P 0.001) such that patients with a longer recovery time tended to have greater levels of fatigue. Of greater relevance in this context, the strength of relationship between recovery time and fatigue was highest right at the end of the dialysis session (r 0.508, P 0.001) and weakens progressively during the time between dialysis sessions (r 0.298, P 0.001) and is weakest before the next dialysis session (r 0.146, P 0.01; Table 2). Because there can be multiple causes of fatigue, many unrelated to dialysis, the steady weakening in the strength of the association the further one gets in time from the dialysis session in question suggests that there is something about the dialysis session itself that is driving the number of minutes to recover and not simply fatigue alone. It also should be noted that the absolute level of fatigue (mean SD) is highest at the end of a dialysis session ( ), drops to the lowest level between dialysis sessions ( ), then rebounds slightly before the next session ( ). This suggests that the pattern of steady weakening and the strength of association between time to recover (minutes) from HD and fatigue is not a simple mathematical artifact reflecting a

7 958 Clinical Journal of the American Society of Nephrology Clin J Am Soc Nephrol 1: , 2006 Figure 1. Time to recover (minutes) shown at time zero and at 3-mo intervals for the daily/nocturnal and control hemodialysis HD patients. Statistical significance shown both within group (*) and between groups (E). steady lessening in fatigue but signifying that there is something about the dialysis session that influences the number of minutes to recovery and that its influence wanes independent of fatigue alone as time passes after dialysis. Examining the correlations between time to recover (minutes) from HD and the Dialysis Stress questionnaire with its subscales (Table 2) shows a significant, moderately strong positive association between minutes to recovery and the total Dialysis Stress score (r 0.348, P 0.001) such that patients who take longer to recover from dialysis report higher levels of dialysis-related stress. In other words, the worse the subjective experience of the dialysis session, the longer the time it takes to recover. The time to recover (minutes) from HD has statistically significant correlation with 10 of the 14 items in the Dialysis Stress scale and include all of the physiologic items except back pain. The strength of these associations ranges from moderate (0.334; P with hypotension ) to weak (0.119; P with vomiting ). Therefore, the time to recover (minutes) from HD seems to be influenced somewhat by a variety of both mutually interrelated and unrelated physical signs and symptoms that can arise during the HD procedure. There is a significant, moderately strong positive association between time to recover (minutes) from HD and total Disease Stress (r 0.374, P 0.001) such that patients who take longer to recover from dialysis report higher levels of disease-related stress. This suggests that the worse the disease symptoms, the longer the time it takes to recover from a dialysis session. Time to recover (minutes) from HD result has statistically significant correlations with all of the 19 items that make up the Disease Stress scale as shown in Table 2. The strength of these relationships range from moderate (0.374; P with aching extremities ) to weak (0.118; P with fear of death or dying ). This suggests a variety of uremia-related physical signs and symptoms have an impact on the time to recover from HD. There is a significant, moderately strong positive association between time to recover (minutes) from HD and total Psychosocial Stress (r 0.328, P 0.001) such that patients who take longer to recover from dialysis report higher levels of interference in their daily lives (Table 2). The time to recover (minutes) from HD has statistically significant correlations with 17 of the 19 items that make up the Psychosocial Stress scale. The strength of these relationships ranges from moderate (0.403; P with interference with child care ) to weak (0.116; P with marriage strain ). Therefore, there seems to be a variety of psychosocial stressors that are having an impact on the time to recover from HD and/or vice versa. There is a significant, weak negative association between time to recover (minutes) from HD and social-leisure activity (r 0.172, P 0.002) such that patients who take longer to recover from dialysis report lower levels of Social-Leisure activity (Table 2). Time to recover (minutes) from HD has statistically significant, mostly weak negative correlations with 12 of the 20 items that make up the socialleisure activity scale, indicating that patients with greater time to recovery from HD engage in these activities slightly less often. Notice that most of these activities are physically demanding (e.g., exercise, sports, shopping). Time to recover (minutes) from HD has statistically significant, positive, weak correlations with two items, namely watching television and listening to the radio and telephone visiting, indicating that patients with greater time to recover from HD engage in these activities slightly more often. Note that these two activities are passive. It also can be seen from Table 2 that time to recover (minutes) from HD has statistically significant negative correlations with all but one of the SF-36 subscales. Given the direction of scoring of SF-36 subscales, this indicates that patients who take longer to recover from an HD session have poorer health and functioning. The stronger associations are with vitality, the physical component summary, and the general health subscales; the weakest associations are with the mental health and health components summary. This suggests that it is physiology more than psychology that is driving the time that it takes a person to recover from dialysis. Table 2 further shows that time to recover (minutes) from HD has a weak negative correlation with the HUI ( 0.232, P 0.001) such that patients who take longer to recover from dialysis have poorer functioning. The HUI subscales with statistically significant although weak positive correlation with time to recover (minutes) from HD are hearing, pain, mobility, and cognition, suggesting that patients who take longer to recover from dialysis also tend to have more pain, less hearing, less mobility, and a lower cognitive function. Here higher subscale scores indicated worse functioning. Evidence of divergent construct validity for time to recover (minutes) from HD comes from a series of correlation analyses indicating no relationship with variables that are known or assumed to be unrelated to the burden of dialysis. With regard to dialysis symptoms, whereas time to recover (minutes) from HD is as stated above related to hypotension, muscle cramps, chest pain, headaches, shivering, vomiting, etc., it is not related to back pain, access problems, dialyzer and line problems, or equipment malfunction (see Table 3). This pattern reinforces the notion that time to recover (minutes) from HD has something to do with the physical and physiologic aspects of dialysis per se. Likewise, there are no correlations with the psychosocial stressors financial problems and interference with vacations. Again, given that these two unrelated items are the only ones in the psychosocial stress scale that have little or nothing to do with

8 Clin J Am Soc Nephrol 1: , 2006 Quality-of-Life Question Related to Recovery after HD 959 underlying health and physical functioning, this suggests a general underlying physiologic mechanism is driving recovery time. With respect to social-leisure activities, it was shown that time to recover (minutes) from HD was negatively associated with more active activities such as sports, exercise, and shopping and was positively correlated with activities of television and radio listening and telephone visiting. As shown in Table 3, time to recover (minutes) from HD is not associated with church attendance or related activity or with other mainly indoor social functions. It is likely that the psychosocial motivations to engage in these activities are strong enough to overcome most barriers that are caused by ill health, supporting (or at least not conflicting with) the notion that time to recover (minutes) from HD is basically physiologically driven. It was indicated previously that time to recover (minutes) from HD correlated with all but one of the SF-36 subscales and that it did so more strongly with the physiologic scales and more weakly with the emotional subscales. This has been interpreted to mean that it is physiology more than psychology driving the length of time that it takes a person to recover from dialysis. This impression is reinforced by the fact that it is the role emotional subscale that lacks the statistically significant relationship with time to recover (minutes) from HD. Table 3 also shows the absence of correlation between time to recover (minutes) from HD and a number of the HUI subscales. One would not expect an association between time to recover (minutes) from HD and the vision, speech, emotion, and possibly the dexterity items of the HUI. One possibly might expect an association with ambulation if time to recover (minutes) from HD is reflecting aspects of health and functioning. This may be the result of patients interpretation of the relevant HUI questions (e.g., the response of a paraplegic or amputee versus the postdialysis fatigued patient who can still walk). Examination of the minutes to recovery results as shown in Table 4 and Figure 1 clearly show that significantly measurable differences are induced by daily/nocturnal HD as compared with conventional thrice-weekly dialysis. This shows that the simple open-ended question indeed is sensitive to change. Conclusion The response to the question, How long does it take you to recover from an HD session? is interpreted easily, is easy to which to respond, shows stability over time by test retest, shows both convergent and divergent validity, and is sensitive to change. As such, it could be considered as a standard question in HD-related studies in which a health-related quality-oflife outcome is examined. Acknowledgments This study was funded by Ontario Ministry of Health and Long- Term Care. A.X.G. was supported by a Canadian Institutes of Health Research Clinician Scientist Award. References 1. Kaplan Denour A: An overview of psychological problems in haemodialysis patients. In: Psychonephrology: Psychological Problems in Kidney Failure and Their Treatment, Vol. 2, edited by Levy NB, New York, Plenum, 1983, pp Evans RW, Manninen DL, Garrison LP Jr: The quality of life of patients with end-stage renal disease. N Engl J Med 312: , Kutner NG, Brogan D, Kutner MH: End-stage renal disease treatment modality and patients quality of life. Am J Nephrol 6: , Park I, Yoo H, Han D, Kim SB, Kim SY, Kim CY, Lee C, Kim HS, Han OS: Changes in the quality of life before and after renal transplantation and comparison of the quality of life between kidney transplant recipients, dialysis patients, and normal controls. Transplant Proc 28: , Heidenheim A, Muirhead N, Moist L, Lindsay R: Patient quality of life on quotidian hemodialysis. Am J Kidney Dis 42[Suppl]: S36 S41, Kjellstrand C, Ting G: Daily hemodialysis: Dialysis for the next century. Adv Ren Replace Ther 5: , Kooistra MP, Vos J, Koomans HA, Vos PF: Daily home haemodialysis in the Netherlands: Effects on metabolic control, haemodynamics and quality of life. Nephrol Dial Transplant 13: , Traeger J, Galland R, Arkouche W, Delawari E, Fouque D: Short daily hemodialysis: A four-year experience. Dial Transplant 30: 76 86, Ting G, Freitas T, Carrie B, Saum N, Kjellstrand C, Zarghamee S: Short daily hemodialysis: Clinical outcomes and quality of life [Abstract]. J Am Soc Nephrol 9: 228A, Brissenden J, Pierratos A, Ouwendyk M, Roscoe J: Improvements in quality of life with nocturnal hemodialysis [Abstract]. J Am Soc Nephrol 9: 168A, Lindsay RM, Leitch R, Heidenheim AP, Kortas C: The London daily/nocturnal hemodialysis study: Study design, morbidity, and mortality results. Am J Kidney Dis 42[Suppl]: S5 S12, Lindsay RM, Heidenheim AP: Measurement of quality of life in international trials involving dialysis patients and the use of recombinant human erythropoietin. In: Erythropoietin: Molecular Physiology and Clinical Applications, edited by Bauer C, Koch K, Scigalla P, Wieczorek L, New York, Dekker, 1994, pp Ware J, Snow K, Kosinksi M, Gandek B: SF-36 Health Survey: Manual and Interpretation Guide. The Health Data Institute of New England Medical Center, Boston, Nimrod, Ware J, Kosinski M, Kellar S: SF-36 Physical and Mental Health Summary Scales: A User s Manual. The Health Data Institute of New England Medical Center, Boston, Nimrod, Furlong W, Feeny D, Torrance GW, Goldsmith CH, De Pauw S, Zhu Z, Denton M, Boyle M: Multiplicative Multi- Attribute Utility Function for the Health Utilities Index Mark 3 (HUI3) System: A Technical Report, Hamilton, McMaster University Centre for Health Economics and Policy Analysis, 1998, pp