Rheumatology International Journal
Clinimetric Properties of WOMAC Index in Greek Knee Osteoarthritis Patients: Comparisons with both Self-reported and Physical Performance Measures
Online Resource - Supplementary Material
AUTHORS:
George Papathanasiou • Sophia Stasi • Leon Oikonomou • Ioanna Roussou •
Effie Papageorgiou • Efstathios Chronopoulos • Nectarios Korres • Nicholas Bellamy
· George Papathanasiou, PΤ, MSc, PhD, Associate Professor, Director of the Physiotherapy Department, Technological Educational Institute of Athens, 24 Mitrodorou St., Athens 10441, Greece.
· Sophia Stasi, PΤ, MSc, Laboratory Associate Lecturer, Physiotherapy Department, Technological Educational Institute of Athens, 24 Mitrodorou St., Athens 10441, Greece.
· Leon Oikonomou, MD, Resident of A΄ Orthopaedic Department, General Hospital of Athens “G. Gennimatas”, 154 Mesogion Ave., Athens 11527, Greece.
· Ioanna Roussou, PΤ, Physiotherapy Department, Technological Educational Institute of Athens, 24 Mitrodorou St., Athens 10441, Greece.
· Effie Papageorgiou, Biostatistician, MSc, PhD, Assistant Professor, General Department of Mathematics, Technological Educational Institute of Athens, Ag. Spyridonos St., Athens 12210, Greece.
· Efstathios Chronopoulos, MD, PhD, Assistant Professor in Orthopaedics, 2nd University Orthopaedic Department, Konstantopoulio Hospital, 3-5 Agias Olgas St., 14388 N. Ionia,Athens, Greece.
· Nectarios Korres, MD, MSc, PhD, Orthopaedic Surgeon, 1st Orthopaedic Department, General Hospital of Attica “KAT”, 2 Nikis str., 14561 Kifissia, Athens, Greece.
· Nicholas Bellamy, MD, MSc MBA DSc FRCP(C) FRCP (Glas,Edin) FACP, FRACP, Professor, School of Medicine,, The University of Queensland, Edith Cavell Building (Room 127), Royal Brisbane and Women’s Hospital, Herston, Queensland 4029, Australia.
CORRESPONDING AUTHOR:
George Papathanasiou
e-mail:
Phone number: 0030-2105385675
Fax number: 0030-2105385674
RESULTS
Validity study
Linear regression analysis
The bidirectional elimination stepwise algorithm was used to select the best variable model and which combination of independent variables provided the best variance explanation of the TUG, VAS/FPS-R and SF-36 scores. Confounders together with WOMAC-function accounted for 49.7% (R2=0.497) of the total variance in the TUG score and together with WOMAC-pain accounted for 54.8% (R2=0.548) in the VAS/FPS-R score. Both WOMAC-function and WOMAC-pain together with the confounders accounted for 78.6% (R2=0.786) and 57.4% (R2=0.574) in SF-36 function and pain respectively.
DISCUSSION
Validity study
There are other WOMAC studies that have presented baseline data or general population-based normative values for the WOMAC Index. However, because of the different methodologies implemented, our results cannot be compared directly with those of previous studies. In these earlier studies, individual data were not provided [1], or the visual analogue format (0-100 mm) instead of the Likert version of the index was used [2], or the participating patients were receiving medication at the beginning of the study [3,4], or patients with knee OA ARA functional class IV were included [5,6,7], or participants’ OA status amongst members of the general population had not been precisely established, other than through self-report [8]. In addition, our findings cannot be compared with those studies that provided WOMAC threshold points (MPCI [2], MCII [3] or PASS [4]). In the latter studies, the presented WOMAC threshold points were determined after therapeutic interventions aimed to measure the degree of improvement in health status achieved by therapy, or to evaluate different cutoff points for different definitions of state-attainment.
REFERENCES
1. Pham T, van der Heijde D, Altman RD, Anderson JJ, Bellamy N, Hochberg M et al (2004) OMERACT-OARSI initiative: osteoarthritis research society international set of responder criteria for osteoarthritis clinical trials revisited. Osteoarthritis Cartilage 12:389-399
2. Ehrich EW, Davies GM, Watson DJ, Bolognese JA, Seidenberg BC, Bellamy N (2000) Minimal perceptible clinical improvement with the Western Ontario and McMaster Universities osteoarthritis index questionnaire and global assessments in patients with osteoarthritis. J Rheumatol 27:2635-2641
3. Tubach F, Ravaud P, Baron G, Falissard B, Logeart I, Bellamy N et al (2005) Evaluation of clinically relevant changes in patient-reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement. Ann Rheum Dis 64(1):29-33
4. Tubach F, Ravaud P, Baron G, Falissard B, Logeart I, Bellamy N et al (2005) Evaluation of clinically relevant states in patient-reported outcomes in knee and hip osteoarthritis: the patient acceptable symptom state. Ann Rheum Dis 64(1):34-37
5. Bellamy N, Bell M, Goldsmith CH, Pericak D, Walker V, Raynauld J-P et al (2005) Evaluation of WOMAC 20, 50, 70 response criteria in patients treated with hylan G-F 20 for knee osteoarthritis. Ann Rheum Dis 64:881-885
6. Xie F, Li SC, Goeree R, Tarride JE, O'Reilly D, Lo NN et al (2008) Validation of Chinese Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients scheduled for total knee replacement. Qual Life Res 17:595-601
7. Konstantinidis GA, Aletras VH, Kanakari K-A, Natsis K, Bellamy N, Niakas D (2013) Comparative validation of the WOMAC osteoarthritis and Lequesne algofunctional indices in Greek patients with hip or knee osteoarthritis. Qual Life Res 22(6). doi:10.1007/s11136-013-0490-x
8. Bellamy N, Wilson C, Hendrikz J (2011) Population-based normative values for the Western Ontario and McMaster (WOMAC) Osteoarthritis Index: part I. Semin Arthritis Rheum 41(2):139-148.
TABLES
Supplementary Table 1. Internal consistency of the Greek version of the WOMAC index.Items / Cronbach’s Alpha
if item deleted *
WOMAC-pain / Overall Alpha: 0.806
1 / 0.724
2 / 0.754
3 / 0.802
4 / 0.798
5 / 0.747
WOMAC-stiffness / Overall Alpha: 0.804
1 / 0.804
2 / 0.804
WOMAC-function / Overall Alpha: 0.956
1 / 0.954
2 / 0.954
3 / 0.953
4 / 0.954
5 / 0.955
6 / 0.952
7 / 0.953
8 / 0.952
9 / 0.952
10 / 0.953
11 / 0.952
12 / 0.955
13 / 0.952
14 / 0.954
15 / 0.952
16 / 0.953
17 / 0.952
WOMAC, WOMAC LK 3.1 Greek for Greece Index.
* when computing Cronbach’s Alpha, “if item deleted” was selected.
Supplementary Table 2. Pearson’s correlations between WOMAC outcomes and SF-36, TUG and VAS/FPS-R scores on day-1 (unadjusted data).
TUG score / VAS/FPS-R / SF36-function / SF36-role physical / SF36-pain
Day-1
WOMAC-total / 0.587 / 0.637 / -0.825 / -0.468 / -0.718
WOMAC-pain / 0.553 / 0.716 / -0.761 / -0.444 / -0.692
WOMAC-stiffness / 0.377 / 0.394 / -0.601 / -0.352 / -0.516
WOMAC-function / 0.668 / 0.632 / -0.875 / -0.474 / -0.744
TUG score / - / 0.646 / -0.647 / -0.358 / -0.501
VAS/FPS-R score / 0.646 / - / -0.616 / -0.483 / -0.558
WOMAC, WOMAC LK 3.1 Greek for Greece Index; SF-36, Short-Form 36 Health Survey; TUG, timed up and go test; VAS/FPS-R, combined visual analogue/faces pain scale - revised. All correlations were significant at p<0.001.
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