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Table 1 Descriptive statistics and intra-practice correlation coefficients

From: Intra-cluster correlation coefficients in adults with diabetes in primary care practices: the Vermont Diabetes Information System field survey

Variable N No Mean or percent SD SE ICC 95% confidence interval
Demographic, social and economic characteristics
Sex (% male) 8808 119.7 48.4   1.3 0.038 0.021, 0.056
Age (years) 8286 117.3 63.1 13.9 0.5 0.077 0.045, 0.109
Married (%) 1004 14.5 62.5   1.6 0.009 0, 0.036
High School Graduate (%) 999 14.4 75.4   1.6 0.011 0, 0.038
Income <$30,000 per year (%) 931 13.4 59.0   2.1 0.042 0.003, 0.081
Private insurance (%) 1001 14.4 58.4   2.0 0.050 0.011, 0.090
Medicare (%) 997 14.4 59.9   1.7 0.018 0, 0.047
Medicaid (%) 995 14.3 21.4   1.8 0.036 0, 0.071
Military or veterans' insurance (%) 994 14.3 5.2   0.8 0.029 0, 0.062
No insurance (%) 993 14.3 2.4   0.6 0.035 0, 0.070
Travel distance from home to Primary Care provider (km) 2955 76.5 13.7 15.3 1.8 0.196 0.102, 0.289
Non-Hispanic white (%) 1004 14.5 97.3   0.5 0.003 0, 0.028
Physical characteristics
Heart Rate (beats per min) 998 14.4 75.0 13.0 0.5 0.015 0, 0.043
Systolic blood pressure (mmHg) 999 14.4 140.3 19.6 0.8 0.042 0.005, 0.079
Diastolic blood pressure (mmHg) 999 14.4 78.3 10.5 0.4 0.017 0, 0.047
Blood pressure below 130/80 mmHg (%) 999 14.4 25.0   1.6 0.028 0, 0.061
Blood pressure over 140/90 mmHg (%) 999 14.4 49.2   2.3 0.069 0.024, 0.114
Height (cm) 998 14.4 165.2 10.4 0.4 0.019 0, 0.048
Weight (kg) 997 14.4 203.0 47.7 1.6 0.011 0, 0.038
Body Mass Index (kg/m2) 994 14.3 33.8 7.4 0.2 0.011 0, 0.039
Body Mass Index >30 kg/m2 (%) 994 14.3 67.2   1.6 0.010 0, 0.038
Laboratory results
Mean glycosolated hemoglobin (A1C) (%) 8711 118.4 7.01 1.45 0.05 0.055 0.032, 0.079
A1C >8.0% (%) 8711 118.4 18.1   1.0 0.025 0.013, 0.037
A1C <7.0 (%) 8711 118.4 61.7   1.6 0.046 0.026, 0.066
Total cholesterol (mg/dl) 8167 112.5 184.4 41.8 1.2 0.037 0.020, 0.054
LDL-cholesterol (mg/dl) 7834 111.0 105.8 34.2 1.0 0.045 0.025, 0.065
LDL <100 mg/dl (%) * 7873 111.6 43.8   1.4 0.029 0.020, 0.055
Triglycerides (mg/dl) 7969 109.8 190.5 161.3 3.3 0.014 0.006, 0.022
Serum creatinine (mg/dl) 8474 115.1 1.12 0.70 0.02 0.080 0.048, 0.112
Urine microalbumin to creatinine ratio (mg/mmol) 3039 46.7 47.0 260.7 10.0 0.101 0.051, 0.152
Urine microalbumin to creatinine ratio <30 mg/mmol (%) 3338 49.0 67.3   1.5 0.031 0.011, 0.051
Quality of care (Process Measures)
Creatinine on time (%) 8808 119.7 79.4   3.1 0.288 0.203, 0.373
Urine microalbumin to creatinine ratio on time (%) 8808 119.7 24.6   2.3 0.162 0.105, 0.219
A1C on time (%) 8808 119.7 50.7   2.4 0.118 0.074, 0.162
Lipids on time (%) 8808 119.7 70.3   3.0 0.199 0.132, 0.265
A1C on time & <7% (%) 7308 113.2 35.5   1.5 0.040 0.021, 0.060
LDL on time & <100 mg/dl (%) 7308 113.2 31.3   1.4 0.040 0.021, 0.059
Influenza vaccine given (%) 995 14.3 80.5   1.4 0.058 0.016, 0.100
Pneumonia vaccine given (%) 913 13.2 70.6   1.8 0.058 0.014, 0.102
Health habits
Alcoholic drinks per week 988 14.2 1.6 4.5 0.2 0.027 0, 0.060
CAGE score (0–4) 946 13.6 0.2 0.7 0.2 0.009 0, 0.038
Tobacco smoker (%) 1006 14.5 16.9   1.2 0.005 0, 0.030
Cigarettes per day 159 2.6 17.2 11.2 1.0 0.086 0, 0.270
Summary of Diabetes Self Care Activities Measure
General diet score 953 13.7 58.4 33.3 1.2 0.017 0, 0.048
Specific diet score 980 14.1 52.2 23.9 0.8 0.011 0, 0.038
Exercise score 992 14.3 34.6 32.7 1.2 0.029 0, 0.062
Blood glucose self-monitoring score 933 13.5 57.9 38.9 1.5 0.051 0.010, 0.093
Foot care score 990 14.3 44.2 35.5 1.2 0.002 0, 0.026
Literacy: Short Test of Functional Health Literacy in Adults
Test score (0–36 points) 1002 14.4 29.7 9.6 0.3 0.017 0, 0.079
Inadequate (0–16) (%) 1002 14.4 10.5   1.0 0.011 0, 0.039
Adequate (23–36) (%) 1002 14.4 82.9   1.5 0.037 0.002, 0.073
Comorbidity
Congestive heart failure (%) 1006 14.5 17.1   1.4 0.025 0, 0.057
Coronary artery disease (%) 1006 14.5 19.3   1.4 0.024 0, 0.056
Peripheral vascular disease (%) 1006 14.5 8.7   1.0 0.006 0, 0.032
Stroke (%) 1006 14.5 11.7   1.1 0.006 0, 0.032
Dementia (%) † 1006 14.5 0.9   0.3 0 § 0, 0.024
Asthma (%) 1006 14.5 20.2   1.4 0.014 0, 0.043
Arthritis (%) 1006 14.5 14.1   1.1 <0.001 0, 0.024
Peptic ulcer disease (%) 1006 14.5 14.3   1.2 0.012 0, 0.040
Cirrhosis (%) 1006 14.5 1.9   0.3 0 § 0, 0.024
Paralysis (%) 1006 14.5 3.0   0.6 0.006 0, 0.032
Renal disease (%) 1006 14.5 5.0   0.6 0 § 0, 0.024
Microvascular complications of diabetes (%) 1006 14.5 16.9   1.2 0.012 0, 0.040
Cancer (%) 1006 14.5 11.9   1.0 0 § 0, 0.024
Leukemia (%) † 1006 14.5 0.6   0.2 0 § 0, 0.024
Lymphoma (%) † 1006 14.5 0.5   0.3 0.018 0, 0.048
Metastatic cancer (%) † 1006 14.5 0.7   0.3 0 § 0, 0.024
HIV disease (%) † 1006 14.5 0.1   0.1 0 § 0, 0.024
Depression (%) 1006 14.5 35.0   1.7 0.007 0, 0.033
Comorbid condition count 1006 14.5 1.8 1.7 0.1 0.031 0, 0.065
Self-reported comorbidity questionnaire score (0–54) 1006 14.5 3.6 3.9 0.2 0.032 0, 0.066
Cardiovascular disease (%) 1006 14.5 30.9   1.6 0.018 0, 0.048
Functional status
SF-12 Physical Component Summary score (0–100) 986 14.2 41.2 12.4 0.5 0.028 0, 0.062
SF-12 Mental Component Summary score (0–100) 986 14.2 50.0 10.7 0.4 0.032 0, 0.061
Patient Health Questionnaire-9 depression score (0–27) 591 11.7 4.1 5.0 0.2 0.006 0, 0.044
Complications of diabetes
Foot ulcer (%) 992 14.3 11.3   1.0 0.009 0, 0.036
Vision problems (%) 950 13.7 20.1   1.3 0 § 0, 0.025
Foot or leg pain (%) 943 13.6 30.9   1.8 0.023 0, 0.055
Stomach emptying problems (%) 901 13.0 6.2   0.8 0.003 0, 0.030
Sexual problems (%) 923 13.3 26.4   1.4 0 § 0, 0.026
Kidney problems (%) 490 10.3 9.2   1.4 0.040 0, 0.096
Medications
Insulin (%) 1006 14.5 18.6   1.4 0.014 0, 0.042
Oral hypoglycemic agent (%) 1006 14.5 66.6   1.7 0.022 0, 0.053
Total medication count (0–29) 1006 14.5 8.8 4.5 0.2 0.028 0, 0.061
Prescription medication count (0–24) 1006 14.5 6.7 3.8 0.2 0.055 0.014, 0.095
Non-prescription medication count (0–15) 1006 14.5 2.0 2.4 0.1 0.059 0.017, 0.101
Audit of Diabetes-Dependant Quality of Life
Do physically 985 14.2 -1.9 2.6 0.1 0.001 0, 0.025
Confidence in ability 982 14.2 -2.0 2.7 0.1 0.004 0, 0.030
Motivation 981 14.2 -1.9 2.7 0.1 0 § 0, 0.025
Freedom to eat 985 14.2 -2.8 2.9 0.1 <0.001 0, 0.025
Enjoyment of food 986 14.2 -2.5 2.9 0.1 0 § 0, 0.025
Future 984 14.2 -0.6 3.8 0.1 0 § 0, 0.025
Freedom to drink 983 14.2 -1.5 2.4 0.1 0 § 0, 0.025
Dependence 982 14.2 -0.6 2.8 0.1 0.004 0, 0.029
Working life 981 14.2 -1.5 2.3 0.1 0.014 0, 0.042
Family life 985 14.2 -0.6 2.7 0.1 0.035 0, 0.070
Social life 983 14.2 -0.9 2.0 0.1 0 § 0, 0.025
Sex life 978 14.1 -1.0 2.4 0.1 0.020 0, 0.051
Physical appearance 980 14.1 -1.1 2.3 0.1 0.012 0, 0.041
Holidays/Leisure 983 14.2 -1.5 2.5 0.1 0 § 0, 0.025
Travel 981 14.1 -1.6 2.6 0.1 0.022 0, 0.054
Society reaction 977 14.1 -0.5 1.6 0.1 0.026 0, 0.058
Finances 978 14.1 -1.7 2.7 0.1 0.009 0, 0.037
Average weighted impact 990 14.3 -1.5 2.0 0.1 0.004 0, 0.029
Resource utilization
Endocrinologist in last year (%) 971 14.0 15.9   2.0 0.089 0.037, 0.140
Dietician in last year (%) 984 14.2 34.3   1.8 0.018 0, 0.048
Podiatrist in last year (%) 984 14.2 23.8   1.6 0.022 0, 0.054
Diabetes Educator in last year (%) 970 14.0 23.8   1.8 0.041 0.004, 0.078
Ophthalmologist in last year (%) 944 13.6 60.4   2.1 0.041 0.003, 0.079
Diabetes class in last year (%) 999 14.4 35.0   1.9 0.035 0.002, 0.073
Emergency Room visits in last year (mean) 994 14.3 0.64 1.46 0.05 0.015 0, 0.044
Health professional visits in last month (mean) 991 14.3 1.63 2.39 0.08 0.035 0, 0.070
  1. N = Subjects analyzed; No = Number per cluster; SD = standard deviation of mean; SE = standard error adjusted for clustering; ICC = Intra-cluster (intra-practice) correlation coefficient.
  2. *In 39 cases in which LDL could not be estimated because triglycerides were over 400 mg/dl, LDL was assumed to be over 100 mg/dl.
  3. † Because only a few subjects have this condition, the ICC may not be estimated consistently.
  4. §The method used truncates the estimate of ICC (and its CI) at 0 for some values that may be negative.