Download presentation

Presentation is loading. Please wait.

Published byJocelyn Melling Modified over 2 years ago

1
SEARO – CSR Training on Outbreak Investigation Two-by-Two Table Cornerstone in epidemiological research

2
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Learning Objectives At the end of the presentation, the participants will be able to: –Use two-by-two table for computation of epidemiological data –Define measures of associate and indicate use

3
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation ‘Every epidemiologic study can be summarized in a two-by-two table.’ - H. Ory

4
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Two-by-two Table Cornerstone of all epidemiological research Often the first thing one draws up when starting to investigate some data

5
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Two-by-two Table Exposed Not exposed ab c d not illill Total b + da + c c + d a + b

6
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation The legend a = ill and exposed b = well and exposed d = well and not exposed c = ill and not exposed exposed not exposed not illill ab dc

7
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Total number exposed ab cd exposed not exposed not illill a + b c + d b + da + c Total number not exposed Total number of cases/ill Total number of controls/not ill The legend Total

8
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Example: New Year’s Dinner Outbreak Food itemIllNot Ill EatenNot EatenEatenNot Eaten Cheesecake4119 Quiche2382 Swiss roll3246 Chocolate cake 1428 Cheese dip4173

9
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Food itemIllNot Ill EatenNot EatenEatenNot Eaten Cheesecake4119 Eat cheesecake Did not eat cheesecake 41 19 not illill 15 b + da + c c + d a + b4 + 1 = 5 1 + 9 = 10 4 + 1 = 51 + 9 = 10 Total

10
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Attack Rate (AR) = Number of population at risk Number of people who are ill Attack rate close to 1 might give us an idea of possible item in question.

11
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Eat cheesecake Did not eat cheesecake 41 19 not illill 15 4 + 1 = 5 1 + 9 = 10 4 + 1 = 51 + 9 = 10 AR = 5 15 = 0.33 Total = AR = 4 5 = 0.8 exposed AR = 1 10 = 0.1 not exposed

12
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Using Denominator Infection by S.Typhimurium Attack Rate by age group, Jura, May-June 1997 Age group (years) Number of Cases <12 1 – 536 6 – 1422 15 – 6429 > 659 Total98

13
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Using Denominator Infection by S.Typhimurium, Attack Rate by age group, Jura, may-June 1997 Age Group (years) Number of CasesPopulationAttack Rate/ 100,000 <12522383 1 – 53616,014225 6 – 142230,38572 15 – 6429157,98918 > 65941,94822 Total98246,85840

14
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Use of Two-By-Two Table in Measures of Association

15
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Relative Risk = the risk in the exposed group divided by the risk in the unexposed group = 8 Relative Risk (RR) = c/(c +d) a/(a + b) = 0.1 0.8 Cohort studies Exposed Not exposed 41 19 not illill b + d a + c c + d a + b 4 + 1 = 5 1 + 9 = 10 4 + 1 = 51 + 9 = 10 Total = 15 RR = 1 no association RR > 1 there is association RR < 1 some way protective

16
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation Odds Ratio = the odds for cases divided by odds for control = 2.25 Case control studies Exposed Not exposed 3025 3260 controlcase b + d a + c c + d a + b 30 + 25 = 55 32 + 60 = 92 30+32 = 62 25+60 = 85 When true size of the exposed and unexposed groups is unknown e.g., cholera cases and control and exposure to shallow well N’Djamena, Chad, July 2001 Odds Ratio (OR) = bc ad = 25 x 32 30 x 60 = 800 1800 OR = 1 no association OR > 1 there is association Open well

17
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation References Giesecke, J. Modern Infectious Disease Epidemiology, 2 nd ed. Oxford University Press. 2002. Gregg, GB. Field Epidemiology, 2 nd ed. Oxford University Press. 2002. Hennekens, C.H., Buring, J.E., Epidemiology in Medicine. 1 st ed. 3 rd printing. Little Brown and Company, 1987.

18
Two-by-Two Table SEARO – CSR Training on Outbreak Investigation

Similar presentations

Presentation is loading. Please wait....

OK

Epidemiological terminology and measures

Epidemiological terminology and measures

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on real numbers for class 9th computer Ppt on different types of computer softwares free Ppt on natural and artificial satellites pictures Ppt on duty roster for boy Ppt on wireless technology Ppt on fire extinguisher types a b Ppt on power system stability pdf Ppt on series and parallel circuits worksheets Ppt on credit policy of a bank Ppt on steps for success