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Table 2 Patient baseline characteristics per group in the study on management of osteoarthritis with a standardized evaluation tool (first motivating example)

From: Propensity score to detect baseline imbalance in cluster randomized trials: the role of the c-statistic

Characteristics Control Standardized tool p SDiff (%)
  n 0=1495 n 1=1462   
  mean (standard deviation) mean (standard deviation)   
Duration of symptoms (months) 68.0 (69.8) 70.9 (75.0) 0.2737 4.03
Age (years) 67.2 (9.7) 66.4 (10.0) 0.0344 7.81
BMI (kg.m −2) 27.8 (4.9) 27.7 (4.7) 0.3824 3.14
Patient global assessment (0-100) 61.1 (18.2) 56.7 (17.4) < 0.0001 24.44
Pain evaluation VAS (0-100) 59.4 (16.0) 55.3 (15.1) < 0.0001 26.32
WOMAC function score (0-100) 45.5 (16.3) 43.8 (16.0) 0.0050 10.32
  n (%) n (%)   
Osteoarthritis in other joints 1366 (91.4) 1311 (89.7) 0.1297 5.81
Prior treatment     
IA treatment 434 (29.0) 432 (29.6) 0.7877 1.14
NSAIDs 955 (63.9) 958 (65.5) 0.3689 3.45
SYSADOA 617 (41.3) 605 (41.4) 0.9810 0.22
Male 424 (28.4) 459 (31.4) 0.0782 6.65
Kellgren and Lawrence grade    0.2594  
III 724 (48.4) 677 (46.3)   4.25
IV 516 (34.5) 547 (37.4)   6.02
  1. BMI: Body Mass Index; VAS: Visual Analogue Scale; WOMAC: Western Ontario and McMaster Universities Arthritis Index; IA: intra-articular; NSAID: non-steroidal anti-inflammatory drug; SYSADOA: systematic slow acting drug for osteoarthritis. SDiff: standardized difference; p: p-value for univariate tests (adjusted t test for quantitative variables, adjusted chi-square test for qualitative variables to take the clustering into account). Bold values are significant tests at a 5 % significance level