Assessment of the Minimum Clinically Important Difference in the Smartphone-based 6-minute Walking Test After Surgery for Lumbar Degenerative Disc Disease.

Abstract

STUDY DESIGN:

Prospective cohort study.

OBJECTIVE:

The aim of this study was to determine the minimum clinically important difference (MCID) of the 6-minute walking test (6WT) after surgery for lumbar degenerative disc disease (DDD).

SUMMARY OF BACKGROUND DATA:

The smartphone-based 6WT is a valid and reliable tool to quantify objective functional impairment in patients with lumbar DDD. To date, the MCID of the 6WT has not been described in patients with DDD.

METHODS:

We assessed patients pre- and 6-weeks postoperatively, analyzing both raw 6-minute walking distances (6WD; in meters) and standardized 6WT z scores. Three methods were applied to compute MCID values using established patient-reported outcomes measures (PROMs) as anchors (VAS back/leg pain, Zurich Claudication Questionnaire [ZCQ], Core Outcome Measures Index [COMI]): average change, minimum detectable change, and the change difference approach.

RESULT:

We studied 49 patients (59% male) with a mean age of 55.5 ± 15.8 years. The computation methods revealed MCID values ranging from 81 m (z score of 0.9) based on the VAS back pain to 99 m (z score of 1.0) based on the ZCQ physical function scale. The average MCID of the 6WT was 92 m (z score of 1.0). Based on the average MCID of raw 6WD values or standardized z scores, 53% or 49% of patients classified as 6-week responders to surgery for lumbar DDD, respectively.

CONCLUSION:

The MCID for the 6WT in lumbar DDD patients is variable, depending on the calculation technique. We propose a MCID of 92m (z score of 1.0), based on the average of all three methods. Using a z score as MCID allows for the standardization of clinically meaningful change and attenuates age- and sex-related differences.Level of Evidence: 3.

• Authors: Anna M Zeitlberger, Marketa Sosnova, Michal Ziga, Luca Regli, Oliver Bozinov, Astrid Weyerbrock, Martin N Stienen, Nicolai Maldaner
• Journal: Spine (Spine (Phila Pa 1976)) Vol. 46 Issue 18 Pg. E959-E965 (Sep 15 2021) ISSN: 1528-1159 [Electronic] United States
• PMID: 34042414 (Publication Type: Journal Article)
• Copyright: Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

Topics

• Back Pain
• Female
• Humans
• Intervertebral Disc Degeneration (surgery)
• Lumbar Vertebrae (surgery)
• Male
• Pain Measurement
• Prospective Studies
• Smartphone
• Treatment Outcome
• Walking