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Table 2 Results of the retrospective cohort study for the analysis of risk.

From: Molecular epidemiology of a hepatitis C virus epidemic in a haemodialysis unit: outbreak investigation and infection outcome

Risk factor

 

Cohort description

Univariate analysis

Multivariate analysis

  

Subjects

Cases

Time at riskA

RateB(95%-CI)

RR (95%-CI)

p-valueC

RR (95%-CI)

p-valueC

Age > 60

No

16

7

428.86

1.63(0.78-3.42)

0.47

0.121

-

-

 

Yes

29

6

781.71

0.77(0.34-1.71)

(0.18-1.22)

   

female sex

No

32

9

869.57

1.03(0.54-1.99)

1.13

0.835

-

-

 

Yes

13

4

341.00

1.17(0.44-3.13)

(0.40-3.22)

   

MWF-am

No

36

12

947.00

1.27(0.72-2.23)

0.30

0.218

-

-

 

Yes

9

1

263.57

0.38(0.05-2.69)

(0.04-2.04)

   

MWF-pm

No

34

4

939.14

0.43(0.16-1.13)

7.79

< 0.001

10.00

0.019

 

Yes

11

9

271.43

3.32(1.73-6.37)

(2.91-20.86)

 

(1.47-68.02)

 

TTS-am

No

36

12

956.14

1.26(0.71-2.21)

0.31

0.236

-

-

 

Yes

9

1

254.43

0.39(0.06-2.79)

(0.05-2.14)

   

TTS-pm

No

34

12

936.29

1.28(0.73-2.26)

0.28

0.202

-

-

 

Yes

11

1

274.28

0.36(0.05-2.59)

(0.04-1.96)

   

Other

No

40

12

1063.71

1.13(0.64-1.99)

0.60

0.626

-

-

 

Yes

5

1

146.86

0.68(0.1-4.83)

(0.08-4.60)

   

Dialysis after gen2 HCV+

No

23

2

467.57

0.43(0.11-1.71)

3.46

0.090

1.29

0.658

 

Yes

22

11

743.00

1.48(0.82-2.67)

(0.82-14.53)

 

(0.13-12.65)

 

Dialysis along gen2 HCV+

No

18

10

578.29

1.73(0.93-3.21)

0.27

0.033

1.70

0.804

 

Yes

27

3

632.28

0.47(0.15-1.47)

(0.08-0.89)

 

(0.16-18.10)

 

N. of dialysis

-

-

-

-

-

0.99 D

0.291

-

-

      

(0.97-1.01)

   

Overa all

-

45

13

1210.57

1.07

-

-

-

-

  1. Forty-five susceptible subjects underwent HD throughout the 33 weeks considered, among them 13 became incident cases with and overall crude rate of 1.07 events per 100 dialysis-week/person. First column risk factor analysed, second column descriptive analysis, third column univariate modified Poisson regression analysis of risk, fourth column multivariate modified Poisson regression. Statistically significant value (p < 0.05) in bold.
  2. A) Time at risk is calculated as week of dialysis person of susceptible subjects; B) the rate is calculated as the number of events per 100 dialysis-week/person; C) p-value is calculated according to Robust standard error; D) estimate increment of risk for each additional HD shift (measure of association are according conventional Poisson regression). RR = rate ratio; CI 95% = 95% confidence interval; gen2 HCV + = genotype 2 hepatitis C virus infected subject; MWF-am = Mondays, Wednesdays and Fridays morning dialysis shift MWF-pm = Mondays, Wednesdays and Fridays afternoon dialysis shift TTS-am = Tuesdays, Thursdays and Saturdays morning dialysis shift TTS-pm = Tuesdays, Thursdays and Saturdays afternoon dialysis shift.