Skip to main content

Table 1 Sociodemographic characteristics and symptoms of enrollees ≥ 5 years of age reported at enrollment, by Polymerase Chain Reaction (PCR)-confirmed Influenza status

From: Classification and Regression Tree (CART) analysis to predict influenza in primary care patients

 

Overall

Developmental sample

Validation sample

Characteristics

 

PCR-negative for influenza

PCR-confirmed influenza

P valuea

  
 

Total

n = 3531

n = 642

 

Total

Total

 

N = 4173

(84.6 %)

(15.4 %)

 

(N = 2087)

(N = 2086)

 

N (%)

n (%)

n (%)

 

N (%)

N (%)

Vaccinated by self-report

354 (8.7)

311 (87.8)

43 (12.2)

0.08

173 (8.5)

181 (8.9)

Unvaccinated

3714 (91.3)

3131 (84.3)

583 (15.7)

   

Smokerb

436 (15.6)

386 (88.5)

50 (11.5)

0.07

215 (15.2)

221 (16)

Non-smoker

2358 (84.4)

2010 (85.2)

348 (14.8)

   

Smoker in the household

481 (11.6)

428 (89.0)

53 (11.0)

0.004

223 (10.7)

258 (12.4)

No smoker in the household

3667 (88.4)

3081 (84.0)

586 (16.0)

   

Asthma diagnosis

1098 (26.8)

949 (86.4)

149 (13.6)

0.04

543 (26.4)

555 (27.1)

No asthma diagnosis

3007 (73.3)

2521 (83.8)

486 (16.2)

   

Any high risk condition

1147 (85.0)

1004 (87.5)

143 (12.5)

0.14

569 (84.4)

578 (85.5)

No high risk condition

203 (15.0)

170 (83.7)

33 (16.3)

   

Symptoms reported at enrollment

  

 Fever

2910 (69.7)

2327 (80.0)

583 (20.0)

<.001

1461 (70)

1449 (69.5)

 No fever

1263 (30.3)

1204 (95.3)

59 (4.7)

   

 Cough

3818 (91.5)

3189 (83.5)

629 (16.5)

<.001

1912 (91.6)

1906 (91.4)

 No cough

355 (8.5)

342 (96.3)

13 (3.7)

   

 Fatigue

3610 (86.5)

3003 (83.2)

607 (16.8)

<.001

1795 (86)

1815 (87)

 No fatigue

563 (13.5)

528 (93.8)

35 (6.2)

   

 Wheezing

1550 (37.1)

1292 (83.3)

258 (16.7)

0.08

773 (37)

777 (37.2)

 No wheezing

2623 (62.9)

2239 (85.4)

384 (14.6)

   

 Sore throat

3105 (74.4)

2639 (85.0)

466 (15.0)

0.25

1543 (73.9)

1562 (74.9)

 No sore throat

1068 (25.6)

892 (83.5)

176 (16.5)

   

 Nasal Congestion

3351 (80.3)

2823 (84.2)

528 (15.8)

0.18

1690 (81)

1661 (79.6)

 No nasal congestion

821 (19.7)

707 (86.1)

114 (13.9)

   

 Shortness of breath

1899 (45.5)

1598 (84.2)

301 (15.8)

0.45

911 (43.7)

988 (47.4)

 No shortness of breath

2272 (54.5)

1931 (85.0)

341 (15.0)

   

Age, years, Mean (SD)

34.1 (22.2)

34.5 (22.2)

31.9 (21.8)

0.007

34.8 (22.3)

33.5 (22)

  1. aFor difference between influenza cases and controls
  2. bAsked of those ≥18 years only