Validation of a Lymphedema-Specific Functional Measure: The Lymphedema Life Impact Scale (LLIS)

Jan Weiss, PT, DHS, CLT-LANACoxHealth, Missouri State University

Introduction Results

Lymphedema manifests as swelling resulting from lymphatic

system failure to remove excess tissue interstitial fluid. Due to the

specific impact of this disease, it is essential for practitioners to have a

condition-specific measure with which to assess the effects of

lymphedema, and upon which to base appropriate treatment. The few

existing lymphedema instruments focus mostly on the impact of upper

extremity lymphedema, use multiple forms, or not been available in

English. The Lymphedema Life Impact Scale (LLIS) was developed as

a comprehensive lymphedema-specific instrument that also addresses

the 2013 Medicare requirement for documentation of functional

outcomes for rehabilitation. The LLIS consists of 18 questions

including physical, functional, and psychosocial domains. The purpose

of this study was to investigate the reliability and validity of the LLIS in

a mixed (upper and lower extremity) lymphedema patient population.

Participants were recruited from Lymphedema and Rehab

Therapy Clinics across the U.S. The sample consisted of 93 patients;

approximately one third of whom had been diagnosed with upper

extremity (UE) lymphedema, one third had lower extremity (LE)

lymphedema and the remaining third comprised of patients at risk for,

but without lymphedema (MHx: obesity, cancer, DVT, CVI) who

served as controls. Participants were an average of 58.19 years old,

were 83.9% female, and almost exclusively white (98.9%). Roughly

half of the sample (51.6%) were employed. The control group was

selected because its members fit diagnostic categories associated

with lymphedema, but had no swelling. More patients with UE

lymphedema had a history of cancer compared to those with LE

lymphedema or the control.

This research suggests that the LLIS works adequately to assess impairments, activity limitations, and participation restrictions in patients with either upper or lower extremity lymphedema. The LLIS demonstrates the following advantages:• The LLIS is construct valid with established measures of

lymphedema, making it useful to practitioners. • The LLIS is lymphedema-specific: it discriminates between

patients with lymphedema and without, even in those patients with risk factors for lymphedema.

• The LLIS provides a single measure for both upper and lower extremity lymphedema eliminating the need for multiple forms of a measure.

• The LLIS measures three types of lymphedema-specific impairment: physical, psychosocial, and functional.

• The LLIS can be used with an Excel worksheet allowing practitioners to calculate Medicare severity codes to comply with the 2013 Medicare requirements for the documentation of functional outcomes for rehabilitation.

• The LLIS is short and quick to administer.

Lawshe (1975). A quantitative approach to content validity. Personnel Psychology, 28, 563-575. doi:10.1111/j.1744-6570.1975.tb01393.x

Todd Daniel, PhDMissouri State University

Content Validity

Reliability

Discriminant Validity

I wish to acknowledge and thank all of the lymphedema therapists and patients across the U.S. who assisted with survey submission. I would also like to thank Dr. Todd Daniel at Missouri State University RStats Institute for his invaluable assistance with statistical analysis and project design.

Participants

References

Content validity was assessed by computing a content validity ratio

(CVR; Lawshe, 1975) for each item, then calculating the average of

the CVRs for a content validity index of the overall measure. Four

subject matter experts rated the items.

All scales on the LLIS produce Cronbach’s alpha values above .80.

Discriminant validity was assessed by comparing LLIS scale scores from patients diagnosed with lymphedema to LLIS scores of those in a control group. The control group was chosen because lymphedema occurs from a variety of etiologies. Using one-way ANOVAs, the LLIS was demonstrated to discriminate between patients with lymphedema and those without lymphedema on all three LLIS scales (Physical: F(2,90) = 42.10, p < .001; Psychosocial: F(2,90) = 24.33, p < .001; Functional: F(2,90) = 29.25, p < .001). Post hoc tests conducted with Tukey HSD showed that for all three scales, the lymphedema patients formed homogeneous subsets distinct from the control group.

Each of the domain scales of the LLIS were correlated with like

domains from functional and quality of life outcome measures currently

used in lymphedema research. The European Organization for

Research and Treatment of Cancer-Quality of Life Questionnaire-Core

30 (EORTC QLQ-C30; Aaronson et al., 1987) is a self-report measure

used to assess quality of life among cancer patients. Although not

specifically designed to be used with lymphedema patients, it is

frequently used in lymphedema research. Not surprisingly, the LLIS

correlations with the EORTC, although statistically significant, were

weaker than with other lymphedema measures. This might indicate

the limited suitability of using a cancer-specific measure with

lymphedema patients. Both the Lymphedema Quality of Life

(LYMQOL; Keeley et al., 2010) and the Disability of Arm, Shoulder, and

Hand (DASH; Institute for Work and Health, 2006) correlated with their

respective scales on the LLIS for UE participants at r = .73 to r = .80

(all statistically significant at the .01 level). The functional scale of the

LLIS correlated reasonably well (r = .538, p < .01) with the Lower

Extremity Functional Scale (LEFS; Binkley et al., 1999), and all three

LLIS scales correlated with their respective scales on the LE LYMQOL

between at r = .74 to r = .88 (all statistically significant at the .01 level).

Summary

Results ResultsConvergent Validity Construct Validity

Limb symptoms, pain, and physical limitations have been

demonstrated to correlate more closely with negative quality of life than

amount of edema. Construct validity was measured through

examination of six symptoms frequently associated with lymphedema.

The LLIS correlated moderately to highly (r = .44 to r = .85) with all

symptoms. This supports the use of the LLIS to provide additional

information about the impact of lymphedema on the individual.