Normative data of a smartphone app-based 6-minute walking test, test-retest reliability, and content validity with patient-reported outcome measures

Publication

Normative data of a smartphone app-based 6-minute walking test, test-retest reliability, and content validity with patient-reported outcome measures

Journal Paper/Review - May 29, 2020

Tosic Lazar, Gautschi Oliver P, Regli Luca, Desai Atman, Sayadi Jamasb Joshua, Gandía-González Maria L, Quddusi Ayesha, Eversdijk Hubert A J, Gadjradj Pravesh S, Staartjes Victor E, Zeitlberger Anna M, Sosnova Marketa, Maldaner Nicolai, Goldberger Elior, Stienen Martin N.

Citation

Tosic L, Gautschi O, Regli L, Desai A, Sayadi J, Gandía-González M, Quddusi A, Eversdijk H, Gadjradj P, Staartjes V, Zeitlberger A, Sosnova M, Maldaner N, Goldberger E, Stienen M. Normative data of a smartphone app-based 6-minute walking test, test-retest reliability, and content validity with patient-reported outcome measures. J Neurosurg Spine 2020:1-10.

Type

Journal Paper/Review (English)

Journal

J Neurosurg Spine 2020

Publication Date

May 29, 2020

Issn Electronic

1547-5646

Pages

1-10

Brief description/objective

OBJECTIVE
The 6-minute walking test (6WT) is used to determine restrictions in a subject's 6-minute walking distance (6WD) due to lumbar degenerative disc disease. To facilitate simple and convenient patient self-measurement, a free and reliable smartphone app using Global Positioning System coordinates was previously designed. The authors aimed to determine normative values for app-based 6WD measurements.

METHODS
The maximum 6WD was determined three times using app-based measurement in a sample of 330 volunteers without previous spine surgery or current spine-related disability, recruited at 8 centers in 5 countries (mean subject age 44.2 years, range 16-91 years; 48.5% male; mean BMI 24.6 kg/m2, range 16.3-40.2 kg/m2; 67.9% working; 14.2% smokers). Subjects provided basic demographic information, including comorbidities and patient-reported outcome measures (PROMs): visual analog scale (VAS) for both low-back and lower-extremity pain, Core Outcome Measures Index (COMI), Zurich Claudication Questionnaire (ZCQ), and subjective walking distance and duration. The authors determined the test-retest reliability across three measurements (intraclass correlation coefficient [ICC], standard error of measurement [SEM], and mean 6WD [95% CI]) stratified for age and sex, and content validity (linear regression coefficients) between 6WD and PROMs.

RESULTS
The ICC for repeated app-based 6WD measurements was 0.89 (95% CI 0.87-0.91, p < 0.001) and the SEM was 34 meters. The overall mean 6WD was 585.9 meters (95% CI 574.7-597.0 meters), with significant differences across age categories (p < 0.001). The 6WD was on average about 32 meters less in females (570.5 vs 602.2 meters, p = 0.005). There were linear correlations between average 6WD and VAS back pain, VAS leg pain, COMI Back and COMI subscores of pain intensity and disability, ZCQ symptom severity, ZCQ physical function, and ZCQ pain and neuroischemic symptoms subscores, as well as with subjective walking distance and duration, indicating that subjects with higher pain, higher disability, and lower subjective walking capacity had significantly lower 6WD (all p < 0.001).

CONCLUSIONS
This study provides normative data for app-based 6WD measurements in a multicenter sample from 8 institutions and 5 countries. These values can now be used as reference to compare 6WT results and quantify objective functional impairment in patients with degenerative diseases of the spine using z-scores. The authors found a good to excellent test-retest reliability of the 6WT app, a low area of uncertainty, and high content validity of the average 6WD with commonly used PROMs.