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Table 2 Covariate balance table and standardised differences of variables included in the propensity score model

From: Comparison of urinary and sexual patient-reported outcomes between open radical prostatectomy and robot-assisted radical prostatectomy: a propensity score matched, population-based study in Victoria

Factor

Unmatched cohort

Matched cohort

ORP

RARP

P value

Standardised difference

ORP

RARP

P value

Standardised difference

N

971

2663

  

3634

3634

  

Age at surgery, mean (SD)

64.9 (6.8)

64.3 (7.1)

0.028

− 8.3%

64.4 (6.9)

64.7 (7.0)

0.100

3.8%

PSA at surgery, mean (SD)

8.4 (6.4)

7.9 (7.4)

0.033

− 8.3%

7.9 (6.1)

8.0 (8.1)

0.510

1.5%

Surgeon years since specialisation, mean (SD)

16.4 (9.3)

15.8 (11.3)

0.120

− 6.0%

16.5 (8.4)

16.4 (11.5)

0.540

− 1.4%

NCCN category

        

Low risk

85 (8.8%)

240 (9.0%)

 < 0.001

 

325 (8.9%)

321 (8.8%)

0.630

 

Intermediate risk

617 (63.5%)

1853 (69.6%)

 

12.8%

2488 (68.5%)

2479 (68.2%)

 

− 0.5%

High risk

236 (24.3%)

526 (19.8%)

 

− 11.0%

733 (20.2%)

760 (20.9%)

 

1.8%

Metastatic

33 (3.4%)

44 (1.7%)

 

− 11.1%

88 (2.4%)

74 (2.0%)

 

− 2.6%

Hospital location

        

Metropolitan

690 (71.1%)

2493 (93.6%)

 < 0.001

 

3161 (87.0%)

3184 (87.6%)

0.420

 

Regional

281 (28.9%)

170 (6.4%)

 

− 61.9%

473 (13.0%)

450 (12.4%)

 

− 1.9%

Hospital type

        

Public

351 (36.1%)

366 (13.7%)

 < 0.001

 

715 (19.7%)

697 (19.2%)

0.590

 

Private

620 (63.9%)

2297 (86.3%)

 

53.6%

2919 (80.3%)

2937 (80.8%)

 

1.3%

IRSAD category

        

1—lowest

112 (11.5%)

224 (8.4%)

 < 0.001

 

274 (7.5%)

376 (10.3%)

 < 0.001

 

2

150 (15.4%)

272 (10.2%)

 

− 15.7%

395 (10.9%)

391 (10.8%)

 

− 0.4%

3

175 (18.0%)

345 (13.0%)

 

− 14.0%

515 (14.2%)

528 (14.5%)

 

1.0%

4

195 (20.1%)

652 (24.5%)

 

10.6%

937 (25.8%)

819 (22.5%)

 

− 7.6%

5—highest

339 (34.9%)

1170 (43.9%)

 

18.5%

1513 (41.6%)

1520 (41.8%)

 

0.4%

Year of surgery

        

2014

153 (15.8%)

417 (15.7%)

0.230

 

467 (12.9%)

552 (15.2%)

0.040

 

2015

194 (20.0%)

598 (22.5%)

 

6.1%

759 (20.9%)

763 (21.0%)

 

0.3%

2016

275 (28.3%)

709 (26.6%)

 

− 3.8%

995 (27.4%)

960 (26.4%)

 

− 2.2%

2017

287 (29.6%)

807 (30.3%)

 

1.6%

1193 (32.8%)

1126 (31.0%)

 

− 4.0%

2018

62 (6.4%)

132 (5.0%)

 

− 6.2%

220 (6.1%)

233 (6.4%)

 

1.5%

  1. Based on the propensity score matching model, the matching process created an observation for each patient if they were to receive the other treatment option and imputed the potential outcome of each observation. Therefore the matched cohort contained double the amount of observations (n = 7268) than the unmatched cohort (n = 3634). Before propensity score matching, standardised differences between ORP and RARP groups exceeded 10% for four of nine analysed covariates (NCCN category, hospital type, hospital location and IRSAD quintile). After propensity score matching, no variables exceeded a standardised difference of 8%
  2. All continuous variables used a two-sample t-test. All binary and categorical variables used the Pearson’s chi-squared test. The matched cohort shows the distribution of covariates after matching for all patients that had answered the urinary bother item, as it had the highest number of responses out of all outcome variables