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Table 2 Individual ICC estimates at centre and surgeon levels

From: Clustering in surgical trials - database of intracluster correlations

   Centre level clustering      Surgeon level clustering     
Outcome Trial N Mean/Prop ICC BC 95% CI BCA 95% CI N Mean/Prop ICC BC 95% CI BCA 95% CI
EQ-5D 1 wk HERNIA 610 0.71 0.029 (0.003, 0.086) (0.004, 0.086) 610 0.71 0.023 (0.003, 0.057) (0.004, 0.070)
EQ-5D 3 m HERNIA 497 0.86 0 (0.000, 0.000)* (., .) 497 0.86 0 (0.000, 0.000)* (., .)
EQ-5D 3 m KATMETAL 361 0.66 0 (0.000, 0.000)* (., .) 361 0.66 0.014 (0.000, 0.104) (0.000, 0.119)
EQ-5D 3 m KATMOBILE 448 0.66 0.06 (0.005, 0.133) (0.007, 0.140) 448 0.66 0.071 (0.021, 0.149) (0.023, 0.159)
EQ-5D 3 m KATPATELLA 1169 0.70 0.008 (0.000, 0.041) (0.000, 0.047) 1169 0.70 0.005 (0.000, 0.032) (0.000, 0.032)
EQ-5D 3 m REFLUX 149 0.79 0.001 (0.000, 0.120) (0.000, 0.105) 104 0.82 0.001 (0.000, 0.120) (0.000, 0.105)
EQ-5D 4 m STARS 277 0.61 0 (0.000, 0.043) (0.000, 0.043) 277 0.61 0.015 (0.000, 0.109) (0.000, 0.112)
EQ-5D 12 m KATMETAL 354 0.71 0.006 (0.000, 0.070) (0.000, 0.070) 354 0.71 0 (0.000, 0.025) (0.000, 0.022)
EQ-5D 12 m KATMOBILE 448 0.70 0.040 (0.004, 0.103) (0.006, 0.107) 448 0.70 0.024 (0.000, 0.080) (0.000, 0.094)
EQ-5D 12 m KATPATELLA 1157 0.74 0.017 (0.000, 0.052) (0.000, 0.061) 1157 0.74 0.040 (0.011, 0.076) (0.013, 0.081)
EQ-5D 12 m REFLUX 152 0.75 0.007 (0.000, 0.107) (0.000, 0.100) 100 0.78 0.002 (0.000, 0.322) (0.000, 0.285)
EQ-5D 12 m STARS 274 0.63 0 (0.000, 0.063) (., .) 274 0.63 0 (0.000, 0.083) (., .)
EQ-5D 60 m KATMETAL 302 0.68 0 (0.000, 0.000)* (., .) 302 0.68 0 (0.000, 0.000)* (., .)
EQ-5D 60 m KATMOBILE 381 0.69 0.015 (0.000, 0.080) (0.000, 0.089) 381 0.69 0.019 (0.000, 0.065) (0.000, 0.076)
EQ-5D 60 m KATPATELLA 997 0.71 0.002 (0.000, 0.021) (0.000, 0.022) 997 0.71 0.009 (0.000, 0.047) (0.000, 0.050)
Oxford knee score 3 m KATMETAL 327 30.14 0 (0.000, 0.000)* (., .) 327 30.14 0.007 (0.000, 0.057) (0.000, 0.059)
Oxford knee score 3 m KATMOBILE 389 29.88 0.073 (0.016, 0.158) (0.020, 0.165) 389 29.88 0.068 (0.018, 0.130) (0.024, 0.142)
Oxford knee score 3 m KATPATELLA 1057 30.89 0.041 (0.014, 0.087) (0.016, 0.092) 1057 30.89 0.05 (0.021, 0.087) (0.021, 0.087)
Oxford knee score 12 m KATMETAL 311 33.71 0.021 (0.000, 0.042) (0.000, 0.042) 311 33.71 0.056 (0.000, 0.130) (0.001, 0.148)
Oxford knee score 12 m KATMOBILE 387 32.99 0.063 (0.023, 0.134) (0.026, 0.144) 387 32.99 0.059 (0.012, 0.134) (0.014, 0.139)
Oxford knee score 12 m KATPATELLA 1010 34.73 0.027 (0.004, 0.071) (0.005, 0.076) 1010 34.73 0.047 (0.015, 0.094) (0.016, 0.101)
Oxford knee score 60 m KATMETAL 284 34.14 0 (0.000, 0.000)* (., .) 284 34.14 0.002 (0.000, 0.021) (0.000, 0.021)
Oxford knee score 60 m KATMOBILE 350 33.43 0.044 (0.000, 0.123) (0.000, 0.160) 350 33.43 0.051 (0.000, 0.121) (0.004, 0.143)
Oxford knee score 60 m KATPATELLA 928 34.90 0.045 (0.016, 0.086) (0.017, 0.090) 928 34.90 0.037 (0.003, 0.074) (0.005, 0.077)
Operating time (min) CLIVIT 483 118.60 0.184 (0.084, 0.373) (0.069, 0.333) 479 118.93 0.392 (0.244, 0.524) (0.257, 0.528)
Operating time (min) DISPACT 344 190.03 0.268 (0.188, 0.418) (0.188, 0.418) 344 190.03 0.395 (0.254, 0.506) (0.259, 0.508)
Operating time (min) FILMS 125 67.55 0.212 (0.009, 0.451) (0.049, 0.486) NA
Closure time (min) INSECT 580 15.02 0.331 (0.129, 0.587) (0.149, 0.661) 579 15.03 0.466 (0.338, 0.593) (0.342, 0.600)
Operating time (min) KATMETAL 398 106.70 0.449 (0.172, 0.726) (0.183, 0.731) 398 106.70 0.514 (0.278, 0.727) (0.302, 0.752)
Operating time (min) KATMOBILE 503 122.37 0.167 (0.092, 0.294) (0.093, 0.295) 503 122.37 0.199 (0.073, 0.390) (0.073, 0.390)
Operating time (min) KATPATELLA 1302 126.75 0.370 (0.254, 0.470) (0.259, 0.478) 1302 126.75 0.445 (0.360, 0.524) (0.369, 0.533)
Operating time (min) REFLUX 108 112.81 0.375 (0.066, 0.623) (0.060, 0.623) 104 113.16 0.375 (0.066, 0.623) (0.060, 0.623)
Operating time (min) STARS 298 62.40 0.072 (0.021, 0.278) (0.022, 0.278) 298 62.40 0.093 (0.003, 0.222) (0.013, 0.248)
Length of stay (days) CLIVIT 488 3.05 0.065 (0.000, 0.367) (0.000, 0.319) 485 3.05 0 (0.000, 0.397) (0.000, 0.345)
Length of stay (days) DISPACT 348 15.41 0.111 (0.012, 0.217) (0.005, 0.210) 348 15.41 0.045 (0.000, 0.307) (0.000, 0.266)
Length of stay (days) INSECT 589 14.59 0.012 (0.000, 0.059) (0.000, 0.049) 588 14.59 0 (0.000, 0.525) (0.000, 0.421)
Length of stay (days) REFLUX 108 2.38 0.345 (0.128, 0.590) (0.146, 0.601) 104 2.38 0.345 (0.128, 0.590) (0.146, 0.601)
Length of stay (days) STARS 298 12.26 0.104 (0.002, 0.354) (0.014, 0.420) 298 12.26 0.104 (0.002, 0.354) (0.014, 0.420)
Fistula DISPACT 352 0.29 0.122 (0.046, 0.301) (0.039, 0.284) 352 0.29 0.084 (0.000, 0.220) (0.000, 0.236)
Complication 6 m FILMS 126 0.38 0 (0.000, 0.000)* (., .) NA
Complication 1 wk HERNIA 717 0.37 0 (0.000, 0.017) (., .) 717 0.37 0.009 (0.000, 0.050) (0.000, 0.053)
Wound infection INSECT 625 0.16 0.01 (0.000, 0.037) (0.000, 0.043) 610 0.16 0.072 (0.000, 0.183) (0.000, 0.186)
HRQ overall score 4 m STARS 276 68.85 0.058 (0.020, 0.207) (0.019, 0.207) 276 68.85 0.114 (0.030, 0.222) (0.032, 0.224)
HRQ overall score 12 m STARS 258 74.04 0 (0.000, 0.093) (0.000, 0.062) 258 74.04 0 (0.000, 0.126) (., .)
HRQ overall score 24 m STARS 236 75.37 0 (0.000, 0.000)* (., .) 236 75.37 0 (0.000, 0.167) (., .)
RQLS score 3 m REFLUX 141 83.85 0.143 (0.000, 0.392) (0.009, 0.449) 100 86.34 0.143 (0.000, 0.392) (0.009, 0.449)
RQLS score 12 m REFLUX 145 84.58 0.058 (0.000, 0.229) (0.000, 0.240) 94 89.10 0 (0.000, 0.263) (., .)
Distance visual acuity (ETDRS) 6 m FILMS 127 60.24 0.175 (0.004, 0.327) (0.013, 0.344) NA
  1. BC 95% CI: Bias corrected bootstrapped 95% confidence interval; BCA 95% CI: Bias corrected and accelerated bootstrapped 95% confidence interval; ETDRS: Early Treatment Diabetic Retinopathy Study; EQ-5D: EUROQOL 5D-3L; HRQ: Hip replacement questionnaire; ICC: Intracluster correlation coefficient; m: month; min: minutes; NA: not applicable; Prop: proportion; RQLS: REFLUX quality of life measure; wk: week.
  2. * 95% bootstrapped confidence interval using percentile method.