Kidney Disease Quality of Life Short Form (KDQOL-SF)

The KDQOL-SF assesses the quality of life of patients with kidney disease. This is accomplished with 43 disease-specific items, 36 generic items and an overall health-ranking item. (Ref: 1) This totals 80 items with 12 disease-specific scales and 8 generic scales and is a short form of the 134-item KDQOL. (Ref: 4) Items of the KDQOL-SF are arranged in these subscales:

Kidney Disease-specific items
Symptom/problem list
Effects of kidney disease
Burden of kidney disease
Work status
Cognitive function
Quality of social interaction
Sexual function
Sleep
Social support
Dialysis staff encouragement
Patient satisfaction
Overall health rating

Generic items
Physical functioning
General health
Pain
Role-physical
Emotional well-being
Role-emotional
Social function
Energy/fatigue

The instrument also contains 14 items regarding background information. Patients are asked to reveal previous hospitalization information, medication taken, specific disease information, education level, gender, race, employment, insurance, income and aid with questionnaire administration. (Ref: 1) The instrument also contains 14 items regarding background information. Patients are asked to reveal previous hospitalization information, medication taken, specific disease information, education level, gender, race, employment, insurance, income and aid with questionnaire administration. (Ref: 1)

Developers used the Goodnight R-Squared improvement procedure to create the KDQOL-SF. This procedure analyzed the KDQOL to find the item per subscale that produces the largest R-value. Items are added one by one until the over all R-Squared value per subscale is at least 0.89. (Ref: 1) To enhance content validity, the developers added additional items: 6 symptoms items, three effects of kidney disease items, one burden of kidney disease item and one item addressing the ability to work full time. (Ref: 1) Lastly, some items were reworded in order to provide better clarity.

Free, with RAND acknowledgement. See “Research Contacts” for availability.

16 minutes. (Ref: 1)

1997

The Flesch-Kincaid reading score is 5.6, which means that a patient reading at 5-6th grade level should not have any complications reading the instrument.

The measure uses a combination of dichotomous scales, yes/no responses and likert-type scales. (Ref: 1)

The scale is designed to be self-administered, but if the patient has trouble reading, a family member or the researcher may help the patient.

Items are precoded with numeric values, such that some items display higher numbers as favorable heath status and other responses display the lower numbers as better health status. These raw scores are transformed to scale scores between 0-100, with the higher scores always reflecting better health status. Each subsection requires a different equation to convert raw scores to scaled scores (subsections have different numbers of items). The last step requires averaging the scaled scores per subscale to obtain a single subscale score. Items that are skipped by the participant is not scored, and hence, not included in the scoring process. (Ref: 1)

There are two known forms of the KDQOL. These are the original form with 134 items and the short form with 80 items. (Ref: 4) The KDQOL-SF is also translated in French, Dutch, Spanish, Italian, German, and Japanese. (Ref: 2-3, http://www.gim.med.ucla.edu/kdqol/)

Ron D Hays, Joel D Kallich, Donna L Mapes, Stephen J Coons, Naseem Amin, William B Carter and Caren Kamberg

The RAND Corporation is copyright holder and makes the KDQOL-SF available free of charge with proper acknowledgment of RAND. (Ref: http://www.gim.med.ucla.edu/kdqol/)

1700 Main Street
P.O. Box 2138
Santa Monica, CA 90407-2138

kdqol@rand.org

www.gim.med.ucla.edu/kdqol/

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Studies compare the local general population to patients with kidney disease, but detailed information was not found regarding the general population. (Ref: 2)

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N/A: self-report instrument.

Developers reported alpha coefficients above the standard 0.70, with exception of Cognitive function (0.68) and quality of social interaction (0.61). (Ref: 1) Researchers studying a group of dialysis patients in Switzerland reported alpha values of 0.70 or higher on the KDQOL-SF subscales with the exception of work status (0.60) and quality of social interaction (0.44) subscales. (Ref: 2)

One study evaluating the Dutch KDQOL-SF used a standard of alpha values of 0.40 or greater to represent overlapping of item score and scale score. Results indicated that work status (0.26) and quality of social interaction (0.26), similar to the French version study, did not overlap the item score with the scale score. Researchers then compared the internal consistency of the Dutch version KDQOL-SF and the original US version. Alpha values for the Dutch version were over the standard 0.70, with the exception of work status, quality of social interaction and social support subscales. The US version was slightly different with alpha values above 0.80, except for cognitive function and quality of social interaction. (Ref: 3)

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One study used the F statistic to compare the SF-36 score of the general U.S. population to scores of patients with kidney disease. Researchers noted that all subscales, with the exception of mental health, were statistically significant (p < 0.001). (Ref: 2) Scores for patients with kidney disease were lower than the scores for the general population group. The KDQOL-SF was compared to the generic HRQOL measure, EuroQol. Researchers reported a positive correlation between the two measures. All subscales were statistically significant with the EuroQol overall health rating, p < 0.05, with the exception of the patient satisfaction subscale. (Ref: 3)

The Spearman correlation technique was used to compare the physical and mental components of the SF-36 to the 12 subscales of the KDQOL-SF. Researchers found the only half of the KDQOL-SF subscales correlated with the physical component. Symptoms/problems and effects of kidney disease was significant p < 0.001 and burden of kidney disease, work status, cognitive function and overall health rating were significant, p < 0.05. All KDQOL-SF subscales correlated significantly to the mental component of the SF-36. Work status, sexual function, dialysis staff encouragement and patient were significant, p< 0.05 and the other were significant (p <0. 001). (Ref: 2) This indicates that there is a significant difference between the general population and patients with kidney disease, especially in the SF-36 physical function component. (Ref: 2)

A research study compared Asian and White patients on three different dialysis treatment modalities. Results revealed that there was no significant difference in physical health, mental health, targeted kidney disease scales and patient satisfaction scores in patients receiving haemodialysis treatment. However, researchers did report significant differences between the ethnic groups when assessing peritoneal dialysis and transplant treatment. Physical health (p=0.045), mental health (p=0.008) and kidney disease targeted (p=0.002) subscales revealed significant differences between ethnic group KDQOL-SF scores for patients undergoing peritoneal dialysis. The Asian population scored lower than the European White group. Scores on the patient satisfaction subscale were not significant. (Ref: 4) Scores of the ethnic groups undergoing the transplant procedure were all significantly different with p values ranging from 0.002 (kidney disease targeted) to 0.011 (patient satisfaction). Asian patients had lower scores in all subscales. (Ref: 4) Scores between treatment modalities were compared and transplant patients scored significantly lower on the KDQOL-SF than the dialysis groups in both ethnic groups. (Ref: 4) Researchers also compared comorbidity scores among the ethnic groups and results were not significant.

Similarly, another study compared scores of the SF-36 among a hemodialysis group, a peritoneal dialysis group and individuals representing the general population and found significant differences between the treatment groups and the general population (p< 0.05). Only the social functioning subscale revealed significant differences between the treatment modalities (p < 0.05). (Ref: 5) The researchers then compared scores of the KDQOL-SF among the peritoneal and hemodialysis patients. All items differed significantly (p < 0.01) between groups with the peritoneal group scoring higher on the dialysis-related symptoms, kidney disease effects, cognitive function, sleep and satisfaction with treatment subscales. (Ref: 5) The hemodialysis group scored higher on the kidney disease burden, social interaction and social support subscales. (Ref: 5)

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Patients completed the KDQOL-SF three months after dialysis treatment and 12 months after treatment. The majority of scores between these periods declined, with the exception of burden of kidney disease, work status, role function physical and mental health. The changes in scores were all not significant. (Ref: 3) Researchers did report increasing significant scores in biological markers such as residual renal function and serum albumin levels. (Ref: 3)

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Yes. (Ref: 1-5)