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Table 1 Effect of 15% DEET repellent over time, treatment, position and person on Anopheles arabiensis in a four-hour repellent evaluation in the semi-field system at Ifakara Health Institute

From: Use of a semi-field system to evaluate the efficacy of topical repellents under user conditions provides a disease exposure free technique comparable with field data

Treatments

Hours

Incidence rate ratio (IRR)1[95% CI]

Z-test statistic2

P-value3

15% DEET in ethanol

1

-

-

-

2

1.744 [0.796-3.819]

1.39

0.164

3

1.223 [0.559-2.675]

0.51

0.613

4

3.708 [1.767-7.780]

3.47

0.001

15% formulated DEET repellent

1

-

-

-

2

0.877 [0.359-2.140]

−0.29

0.774

3

1.674 [0.756-3.709]

1.27

0.204

4

3.439 [1.601-7.386]

3.17

0.002

Treatments

    

Placebo

-

-

-

-

15% DEET in ethanol

-

0.082 [0.045-0.149]

−8.23

<0.0001

15% DEET in lotion format

-

0.077 [0.042-0.142]

−8.21

<0.0001

Position

    

1

-

-

-

-

2

-

0.818 [0.587-1.139]

−1.19

0.236

3

-

2.000 [1.506-2.656]

4.79

<0.0001

Person

    

1

-

-

-

-

2

-

0.619 [0.441-0.868]

−2.78

0.005

3

-

2.372 [1.796-3.133]

6.08

<0.0001

  1. 1The data for position one, person one and effect of treatments in hour one were used as a reference values for calculating the incidence rate ratios (IRR) for mosquito bites. 2The test statistic z is the ratio of the Coefficient to the Standard error of that respective predictor and is used to test against a two-sided alternative hypothesis that the Coefficient is not equal to zero. 3The probability (P) that a particular z test statistic is different to what has been observed under the null hypothesis.