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Table 3 Encounter 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

Encounter 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.

%

      

Syndrome type:

            

   Fever

371

12.5

230

16.9

601

13.9

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Gastrointestinal

572

19.3

283

20.8

855

19.8

1.57

(1.25, 1.97)

< 0.0001

1.72

(1.36, 2.16)

< 0.0001

   Neurological

608

20.5

363

26.6

971

22.4

1.29

(1.05, 1.60)

0.02

1.38

(1.11, 1.72)

< 0.01

   Rash

628

21.2

269

19.7

897

20.7

1.80

(1.44, 2.25)

< 0.0001

1.89

(1.51, 2.37)

< 0.0001

   Respiratory

808

27.2

241

17.7

1049

24.2

1.72

(1.36, 2.17)

< 0.0001

1.66

(1.29, 2.14)

< 0.0001

   ILI

555

18.7

98

7.2

653

15.1

2.98

(2.32, 3.82)

< 0.0001

2.68

(2.06, 3.48)

< 0.0001

Type of clinic:

            

   Private clinic

2,916

98.3

1,320

96.9

4,236

97.8

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Community health center

10

0.3

8

0.6

18

0.4

0.58

(0.14, 2.35)

0.45

0.46

(0.11, 2.01)

0.30

   Hospital-based ambulatory clinic

41

1.4

35

2.6

76

1.8

0.53

(0.30, 0.93)

0.03

0.75

(0.37, 1.53)

0.43

Geographic location of clinic:

            

   Urban

2,476

83.5

1,169

85.8

3,645

84.2

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Rural

491

16.6

194

14.2

685

15.8

1.20

(0.99, 1.46)

0.07

1.19

(0.98, 1.45)

0.08

Physician familiarity with the patient (patient treated by the study physician in the previous year):

            

   No

1,199

40.4

475

34.9

1,674

38.7

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Yes

1,768

59.6

888

65.1

2,656

61.3

0.79

(0.69, 0.91)

< 0.001

0.95

(0.82, 1.11)

0.53

Day of the week:

            

   Weekday

2,797

94.3

1,308

96.0

4,105

94.8

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Weekend

170

5.7

55

4.0

225

5.2

1.42

(1.03, 1.95)

0.03

1.28

(0.92, 1.77)

0.15

Season:

            

   Winter (12/22-03/20)

737

24.8

339

24.9

1,076

24.9

Ref.

Ref.

Ref.

Ref.

Ref.

Ref.

   Spring (03/21-06/20)

855

28.8

317

23.3

1,172

27.1

1.22

(1.02, 1.47)

0.03

1.29

(1.07, 1.57)

0.01

   Summer (06/21-09/22)

645

21.7

351

25.8

996

23.0

0.84

(0.70, 1.01)

0.06

0.91

(0.75, 1.10)

0.33

   Fall (09/23-12/21)

730

24.6

356

26.1

1,086

25.1

0.94

(0.79, 1.12)

0.48

0.97

(0.81, 1.17)

0.79

 

Mean

SD

Mean

SD

Mean

SD

      

No. visits for the same syndrome billed by the study physician in the previous 30 days (per 10 visits)

4.1

6.7

4.2

6.2

4.2

6.6

1.08

(0.95, 1.23)

0.25

1.05

(1.01, 1.08)

0.01

Physician workload: no. claims billed that day (per 10 claims)

35.1

17.4

36.5

21.0

35.5

18.6

0.96

(0.93, 1.00)

0.03

0.93

(0.90, 0.97)

< 0.001

  1. 1 Multivariate analysis adjusted for all encounter characteristics in Table 3, all physician characteristics in Table 1, and all patient characteristics in Table 2.