Intra-cluster and inter-period correlation coefficients for cross-sectional cluster randomised controlled trials for type-2 diabetes in UK primary care

Table 5 Intra-cluster correlation coefficients (ICCs) for binary outcomes for included patients from THIN database

		Logistic regression model		Linear model
Outcome	Prevalence of outcome	ICC from unadjusted model (SE)	ICC from adjusted model (SE)	ICC from unadjusted model (SE)	ICC from adjusted model (SE)
Clinical measures
HbA1c (%) (>7.5)	0.342	0.035 (0.003)	0.037 (0.003)	0.026 (0.002)	0.027 (0.002)
Systolic blood pressure (mmHg) (>140)	0.252	0.069 (0.005)	0.066 (0.005)	0.039 (0.003)	0.036 (0.003)
Systolic blood pressure (mmHg) (>130)	0.572	0.047 (0.004)	0.044 (0.003)	0.038 (0.003)	0.035 (0.003)
Diastolic blood pressure (mmHg) (>80)	0.235	0.086 (0.006)	0.088 (0.007)	0.046 (0.004)	0.045 (0.003)
BMI (kg/m²) (>30)	0.483	0.019 (0.002)	0.022 (0.002	0.015 (0.001)	0.016 (0.002)
BMI (kg/m²) (>25)	0.831	0.022 (0.002)	0.022 (0.002)	0.011 (0.001)	0.010 (0.001)
Total cholesterol (mmol/L) (>4)	0.504	0.025 (0.002)	0.024 (0.002)	0.020 (0.002)	0.019 (0.002)
HDL cholesterol (mmol/L) (<1.2)	0.503	0.035 (0.002)	0.036 (0.003)	0.029 (0.002)	0.027 (0.002)
Medication
Taking of insulin	0.591	0.113 (0.007)	0.109 (0.007)	0.081 (0.006)	0.077 (0.005)
Clinical outcomes
Atrial fibrillation	0.01058	0.020 (0.009)	0.016 (0.009)	0.001 (0.000)	0.001 (0.000)
Chronic kidney disease	0.00349	0.140 (0.026)	0.136 (0.026)	0.003 (0.000)	0.003 (0.000)
Chronic obstructive pulmonary disease	0.00801	0.070 (0.015)	0.064 (0.015)	0.002 (0.000)	0.002 (0.000)
Ischaemic heart disease	0.01109	0.027 (0.011)	0.027 (0.011)	0.001 (0.000)	0.001 (0.000)
Peripheral vascular disease	0.00545	0.130 (0.020)	0.124 (0.020)	0.005 (0.001)	0.005 (0.001)
Stroke	0.00426	0.274 (0.031)	0.261 (0.031)	0.010 (0.001)	0.010 (0.001)

BMI body mass index, HbA1c glycosylated haemoglobin, HDL high-density lipoprotein, SE standard error

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