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Table 2 Patient characteristics associated with accuracy of syndrome definitions based on physician claims (OR >1.00 means the encounter characteristic increased the PPV of the syndrome definition, OR < 1.00 means the encounter characteristic reduced the PPV)

From: Patient, physician, encounter, and billing characteristics predict the accuracy of syndromic surveillance case definitions

 

No. visits with a syndrome-positive physician claim

Bivariate regression analysis

Multivariate regression analysis1

Patient characteristics

Syndrome-positive in the chart

(N = 2,967)

Syndrome-negative in the chart

(N = 1,363)

Total

(N = 4,330)

OR

95% CI

P value

OR

95% CI

P value

 

No.

%

No.

%

No.

%

      

Sex:

            

   Female

1,810

61.0

824

60.5

2,634

60.8

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Male

1,157

39.0

539

39.5

1,696

39.2

0.98

(0.86, 1.12)

0.75

0.89

(0.77, 1.03)

0.11

Material deprivation index:2

            

   1st quintile (least deprived)

524

17.7

284

20.8

808

18.7

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   2nd quintile

584

19.7

270

19.8

854

19.7

1.16

(0.94, 1.42)

0.16

1.18

(0.95, 1.46)

0.14

   3rd quintile

604

20.4

243

17.8

847

19.6

1.33

(1.08, 1.64)

0.01

1.44

(1.15, 1.81)

< 0.01

   4th quintile

581

19.6

261

19.1

842

19.4

1.21

(0.98, 1.49)

0.07

1.25

(1.01, 1.55)

0.04

   5th quintile (most deprived)

545

18.4

255

18.7

800

18.5

1.16

(0.94, 1.43)

0.16

1.21

(0.97, 1.50)

0.09

Social deprivation index:2

            

   1st quintile (least deprived)

611

20.6

251

18.4

862

19.9

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   2nd quintile

574

19.3

263

19.3

837

19.3

0.90

(0.73, 1.10)

0.30

0.91

(0.74, 1.13)

0.41

   3rd quintile

572

19.3

251

18.4

823

19.0

0.91

(0.74, 1.13)

0.41

0.97

(0.77, 1.21)

0.76

   4th quintile

554

18.7

261

19.1

815

18.8

0.87

(0.70, 1.07)

0.19

0.88

(0.70, 1.10)

0.26

   5th quintile (most deprived)

527

17.8

287

21.1

814

18.8

0.75

(0.61, 0.93)

0.01

0.76

(0.60, 0.95)

0.02

Deprivation indices missing:

            

   No

2,838

95.7

1,313

96.3

4,151

95.9

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Yes

129

4.3

50

3.7

179

4.1

1.04

(0.73, 1.49)

0.83

1.06

(0.68, 1.64)

0.81

 

Mean

SD

Mean

SD

Mean

SD

      

Age (age per 5 years is used in the regression analyses)3

36.4

24.9

43.2

24.0

38.5

24.8

0.95

(0.93, 0.96)

< 0.0001

0.96

(0.94, 0.97)

< 0.0001

Health services utilization (no. ambulatory care visits in the previous year)4

9.0

10.1

10.6

12.7

9.5

11.0

0.99

(0.98, 0.99)

< 0.0001

0.99

(0.99, 1.00)

0.08

Charlson comorbidity index (per 1-point increase)4

0.38

0.98

0.49

1.17

0.42

1.04

0.92

(0.86, 0.97)

< 0.01

0.98

(0.92, 1.05)

0.58

  1. 1 Multivariate analysis adjusted for all patient characteristics in Table 2, all physician characteristics in Table 1, and all encounter characteristics in Table 3
  2. 2 The material and social deprivation indices were calculated using Statistics Canada's 2006 census data. These indices were developed by the Quebec National Public Health Institute. The material deprivation index summarizes information on the proportion of persons who have no high school diploma, the proportion of persons employed, and the average income in the patient's 6-digit postal code area of residence. The social deprivation index summarizes information on the proportion of single-parent families, the proportion of persons living alone, and the proportion of persons separated, divorced, or widowed in the patient's 6-digit postal code area of residence.
  3. 3 On October 1st of the study year when the visit took place. The study spanned 2 years: October 1, 2005 to September 30, 2006, and October 1, 2006 to September 30, 2007.
  4. 4 Based on all medical services claims billed by all Quebec physicians (not only the 3,600 study physicians) in the year prior to the date of the syndrome-positive visit.
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BMC Public Health

ISSN: 1471-2458

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