Osteoarthritis VAS Pain Scores Correlate With WOMAC Weight-Bearing Pain Scores

Visual analog scale (VAS) pain scores were found to correlate most strongly with Western Ontario and McMaster University Arthritis Index (WOMAC) weight-bearing scores among patients with osteoarthritis, according to the results of study published in Pain Reports.

Investigators from NBCD A/S, a biotechnology contract research organization in Denmark, sourced data for this study from 2 phase 3 clinical trials (ClinicalTrials.gov Identifiers: NCT00486434 and NCT00704847) that investigated the efficacy and safety of oral salmon calcitonin in patients with osteoarthritis. This cross-sectional study evaluated the correlation between VAS and WOMAC pain domains.

The mean age of study participants (N=2093) was 64.4 (range, 6.8) years, 34.8% were men, mean body mass index (BMI) was 28.9 (SD, 4.9) kg/m², and 2.5% had Kellgren-Lawrence (KL) radiologic grade 4 osteoarthritis severity in the nontarget knee.

The average 100-point VAS pain score was 50.83 (standard deviation [SD], 20.46) points, and the average 100-point WOMAC pain score was 48.37 (SD, 14.67) points.

The 2 pain scores were found to correlate (r, 0.67; P <.0001). When stratifying the WOMAC score into weight-bearing pain and nonweight-bearing pain components, a stronger correlation with VAS scores were observed for weight-bearing scores (r, 0.68; P <.0001) than for nonweight-bearing scores (r, 0.55; P <.0001).

Stratified by quintiles of VAS and the 5 components of the WOMAC, the WOMAC walking score correlated with all but the second quintile VAS (r range, 0.11-0.31; all P ≤.05), the WOMAC stairs score correlated with all VAS quintiles (r range, 0.10-0.34; all P ≤.02), the WOMAC nocturnal scores correlated with the first (r, 0.18; P <.001) and fifth (r, 0.28; P <.001) VAS quintiles, the WOMAC rest scores correlated with all but the third and fourth VAS quintiles (r range, 0.07-0.28; all P ≤.003), and the WOMAC standing score correlated with the first (r, 0.33; P <.001) and second (r, 0.06; P <.001) VAS quintiles.

The discordance in VAS and WOMAC scores was associated with the KL grade of the nontarget knee (P =.002), in which the greater divergence in VAS and WOMAC scores was found to be associated with greater KL grade (P =.02). The relationship with KL grade was even larger with the discordance between VAS and weight-bearing WOMAC scores (P <.0001).

This study may have been limited by the majority of patients experiencing mild to moderate disease.

Study authors concluded, “The 24-hour single-question VAS pain scale and the pain subscale of WOMAC were moderately correlated. Our results suggest that VAS pain scale correlated more accurately with the weight-bearing construct of WOMAC pain subscale as compared with the WOMAC pain nonweight-bearing construct. Agreement between VAS pain and WOMAC pain was best in the extreme ranges of the scale.”

Disclosure: Multiple study authors are employed by or are shareholders of NBCD A/S. Please see the original reference for a full list of authors’ disclosures.