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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