Table 2

Unadjusted and Adjusted odds of response by patient characteristics and incentive condition

First Mailing/Reminder postcard

Final Response

$2

$5

Unadjusted

p-value*

Adjusted odds of responding with $5 incentive vs. $2 incentive **

$2

$5

p-value*

Adjusted odds of responding with $5 incentive vs. $2 incentive**


Overall Response Rate (Cumulative)

47.67%

N = 317

57.77%

N = 383

0.0002

1.50 (1.21-1.86)

65.41%

N = 435

67.27%

N = 446

0.4741

1.09 (0.87-1.36)

Age

0.0007

0.7525

< 50

32.02%

41.29%

1.49 (1.01-2.22)

49.56%

50.25%

1.03 (0.70-1.50)

50-75

54.71%

62.73%

1.39 (0.95-2.04)

71.30%

72.73%

1.07 (0.71-1.63)

> 75

57.01%

66.94%

1.53 (1.04-2.23)

76.17%

76.45%

1.02 (0.66-1.57)

Race

0.0002

0.6142

Caucasian

58.33%

68.42%

1.55 (1.18-2.03)

78.07%

78.07%

1.00 (0.73-1.37)

African American

30.48%

44.44%

1.83 (1.05-3.17)

52.38%

56.41%

1.77 (0.69-2.00)

Other

18.27%

21.11%

1.20 (0.59-2.43)

23.08%

26.67%

1.21 (0.63-2.33)

Sex

0.0008

0.6642

Female

31.75%

41.30%

1.51 (0.86-2.65)

56.35%

51.09%

.081 (0.47-1.39)

Male

51.39%

60.42%

1.44 (1.14-1.83)

67.53%

69.88%

1.12 (0.87-1.44)

Marital Status

0.0002

0.4799

Married/Living with someone

53.04%

69.70%

2.04 (1.50-2.76)

72.38%

76.58%

1.25 (0.89-1.74)

Not Married

41.25%

43.33%

1.09 (0.79-1.50)

57.10%

56.00%

0.96 (0.69-1.32)

Charlson Comorbidity Score

0.0003

0.5408

0

43.97%

52.86%

1.43 (1.03-1.98)

60.26%

63.21%

1.13 (0.81-1.58)

1

44.44%

29.23%

1.57 (0.98-2.51)

64.44%

34.86%

1.09 (0.67-1.78)

2+

54.71%

64.96%

1.53 (1.05-2.24)

73.09%

72.65%

0.98 (0.65-1.48)

Mental health diagnoses

0.0003

0.4929

No Mental Health Diagnosis

54.55%

62.66%

1.40 (1.02-1.92)

70.78%

72.47%

1.09 (0.77-1.54)

Substance abuse only

41.38%

58.62%

2.01 (0.96-4.20)

60.34%

68.97%

1.46 (0.68-3.14)

Psychiatric only

43.09%

55.62%

1.66 (1.10-2.50)

64.89%

64.04%

0.96 (0.63-1.48)

Dual diagnosis

39.64%

46.85%

1.34 (0.79-2.29)

54.05%

56.76%

1.12 (0.66-1.89)

Rural/Urban Status

0.0007

0.6519

Urban

46.43%

55.98%

1.47 (1.17-1.84)

64.82%

65.45%

1.03 (0.81-1.30)

Rural

70.59%

75.41%

1.28 (0.50-3.27)

76.47%

85.25%

1.78 (0.61-5.14)


*p-values from chi-square test.

**Logistic regression model included predictor, sex, rural/urban status; bolded odds ratios are statistically significant.

Griffin et al. BMC Medical Research Methodology 2011 11:81   doi:10.1186/1471-2288-11-81

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