TABLE 18

Estimates of arm difference in primary outcome for models which do or do not account for possible clustering effects

ModelArm difference: SF-36v2 PCS at 6 monthsa95% CIp-valueICCLikelihood ratio test vs linear (p-value)AIC
FE−0.01−0.80 to 0.790.990113,528.62
FE + RE intercept for: PCT−0.003−0.80 to 0.790.990.0050.0113,533.55
FE + RE intercept and slope for: PCT−0.01−0.80 to 0.780.98Intercept: PCT < 0.001 Slope: baseline PCS < 0.001 Age < 0.0010.1113,534.29
FE + RE intercept for: GP practice−0.01−0.80 to 0.780.980.0040.2913,530.30
FE + RE intercept and slope for: GP practice−0.01−0.80 to 0.780.98Intercept: practice = 0.002 Slope: baseline PCS < 0.001 Age < 0.0010.9513,534.29
FE + RE intercept for: PCT and GP practice−0.01−0.80 to 0.780.98Intercept: PCT = 0.005 Practice = 0.0050.0713,535.00
FE + RE intercept and slope for: PCT and GP practice−0.01−0.80 to 0.780.97Intercept: PCT < 0.001 Practice = 0.002 Slope: baseline PCS < 0.001 Age < 0.0010.3513,541.72

FE, fixed effect; LR test, likelihood ratio test; RE, random effect.

a

Adjusted for outcome baseline, sex, age, referral problem, PCT.

From: Chapter 3, Randomised controlled trial: results

Cover of A pragmatic randomised controlled trial of the effectiveness and cost-effectiveness of ‘PhysioDirect’ telephone assessment and advice services for physiotherapy
A pragmatic randomised controlled trial of the effectiveness and cost-effectiveness of ‘PhysioDirect’ telephone assessment and advice services for physiotherapy.
Health Technology Assessment, No. 17.2.
Salisbury C, Foster NE, Hopper C, et al.
Southampton (UK): NIHR Journals Library; 2013 Jan.
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