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. 2018 Jul 31;16(1):154.
doi: 10.1186/s12955-018-0979-7.

Health-related Quality of Life in Relation to Symptomatic and Radiographic Definitions of Knee Osteoarthritis: Data From Osteoarthritis Initiative (OAI) 4-year Follow-Up Study

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Free PMC article

Health-related Quality of Life in Relation to Symptomatic and Radiographic Definitions of Knee Osteoarthritis: Data From Osteoarthritis Initiative (OAI) 4-year Follow-Up Study

Soili Törmälehto et al. Health Qual Life Outcomes. .
Free PMC article

Abstract

Background: The purpose was to quantify the decrement in health utility (referred as disutility) associated with knee osteoarthritis (OA) and different symptomatic and radiographic uni- and bilateral definitions of knee OA in a repeated measures design of persons with knee OA or at increased risk of developing knee OA.

Methods: Data were obtained from the Osteoarthritis Initiative database. SF-12 health-related quality of life was converted into SF-6D utilities, and were then handled as the health utility loss by subtracting 1.000 from the utility score, yielding a negative value (disutility). Symptomatic OA was defined by radiographic findings (Kellgren-Lawrence, K-L, grade ≥ 2) and frequent knee pain in the same knee. Radiographic OA was defined by five different definitions (K-L ≥ 2 unilaterally / bilaterally, or the highest / mean / combination of K-L grades of both knees). Repeated measures generalized estimating equation (GEE) models were used to investigate disutility in relation to these different definitions.

Results: Utility decreased with worsening of symptomatic or radiographic status of knee OA. The participants with bilateral and unilateral symptomatic knee OA had 0.03 (p < 0.001) and 0.02 (p < 0.001) points lower utility scores, respectively, compared with the reference group. The radiographic K-L grade 4 defined as the mean or the highest grade of both knees was related to a decrease of 0.04 (p < 0.001) and 0.03 (p < 0.001) points in utility scores, respectively, compared to the reference group.

Conclusions: Knee OA is associated with diminished health-related quality of life. Health utility can be quantified in relation to both symptomatic and radiographic uni- and bilateral definitions of knee OA, and these definitions are associated with differing disutilities. The performance of symptomatic definition was better, indicating that pain experience is an important factor in knee OA related quality of life.

Keywords: Health-related quality of life; Knee osteoarthritis; SF-12; SF-6D.

Conflict of interest statement

Ethics approval and consent to participate

This article was prepared using an Osteoarthritis Initiative (OAI) public-use data set (http://www.oai.ucsf.edu/). Ethical approval for collecting all subject information was provided by the OAI, and informed consent was obtained from all individual participants included in the study. This article does not contain any studies with human participants performed by any of the authors. Access, download and analyses of the OAI data were performed under the OAI Data Use Agreement.

Consent for publication

Not applicable

Competing interests

ST has been a paid employee of Medfiles Ltd., and is the founder of MediSoili Oy. JM is a founding partner of ESiOR Oy. These companies were not involved in carrying out this research. All other authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
The flow diagram of the OAI study participants and number of observations. * Pain questionnaire required for the definition of symptomatic knee OA (K-L grade ≥ 2 and knee pain on more than half the days during past month in the same knee)
Fig. 2
Fig. 2
SF-6D disutility scores in relation to symptomatic and radiographic knee OA definitions. a 2-scale symptomatic knee OA (K-L grade ≥ 2 and frequent knee pain in the same knee in at least one knee) b 2-scale radiographic knee OA (K-L grade ≥ 2 in at least one knee) c 3-scale symptomatic knee OA (K-L grade ≥ 2 and frequent knee pain in the same knee) d 3-scale radiographic knee OA (K-L grade ≥ 2). Disutility of the best health state possible (no OA) is set as the horizontal reference line (dotted). Other horizontal lines (dotted) are set in 0.027 point intervals representing 1.0 MID (minimally important difference). Error bars are 95% confidence intervals. The mean difference is significant at the 0.05 level (*) in comparison to the best health state (no OA)
Fig. 3
Fig. 3
SF-6D disutility scores in relation to 5- and 9-scale radiographic knee OA definitions. a 5-scale radiographic knee OA (the highest K-L grade in both knees) or b 9-scale radiographic knee OA (mean of K-L grades in both knees). Disutility of the best health state possible (K-L grade 0) is set as the horizontal reference line (dotted). Other horizontal lines (dotted) are set in 0.027 point intervals representing 1.0 MID (minimally important difference). Error bars are 95% confidence intervals. The mean difference is significant at the 0.05 level (*) in comparison to the best health state (K-L grade 0)
Fig. 4
Fig. 4
SF-6D disutility scores in relation to 15-scale radiographic knee OA definition. 15-scale radiographic knee OA (combination of K-L grades in both knees). Disutility of the best health state possible (K-L grade 0;0) is set as the horizontal reference line (dotted). Other horizontal lines (dotted) are set in 0.027 point intervals representing 1.0 MID (minimally important difference). Error bars are 95% confidence intervals. The mean difference is significant at the 0.05 level (*) in comparison to the best health state (K-L grade 0;0)

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