Measurements in epidemiology

1. Measurement in epidemiology .

2. Components of epidemiology:-

3. Mortality. Morbidity. Disability. Presence & absence or distribution of.. Medical needs. Utilization of health services. Demographic variables. Scope of measurement:-

4. Tools of measurements-

5. Rate Measures the occurrence of an event or disease in a given population during a given period (one Year). (Birth rate, growth rate, accident rate) Usually expressed per 100 or per1000 population. It has a time dimension, whereas a PROPORTION does not. 

6. A fraction is made up of 2 numbers. The top number is called the NUMERATOR and the bottom number is called the DENOMINATOR. In the fraction ¾ the 3 is the numerator and the 4 is the denominator.

7. No of death in one year Death rate= -------------------- X 1000 Total mid year population Numerator Denominator. Time specification Multiplier (Numerator is part of denominator ) Rate comprises-

8. The value obtained by dividing one quantity by another - X/Y. Male to female ratio.   A ratio often compares two rates, death rates for women and men at a given age.  Ratio

9. Ratio- Ratio also expresses relation of size between the two quantities. Numerator is not part of Denominator. Expressed as X / Y. Doctor : Population ratio. Male : Female ratio. WBC : RBC ratio

10. A part/share or number considered in comparative relation to a whole. "the proportion of greenhouse gases in the atmosphere is rising” Usually expressed as a percentage % Proportion -

11. Proportion- This is also relation /magnitude between two quantities, And numerator is always part of denominator . And expressed as percentage -Proportion of female students . -Proportion of anemic mothers (60% mothers are anemic )

12. Measurement of morbidity-

13. Measurement of morbidity-

14. Prevalence:- how many people in a population currently have the disease (Photograph) Incidence:- how many people are diagnosed each year (Film) Prevalence vs. Incidence

15. Cure rate

16. New cases

17. Special incidences

18. Types of prevalence-

19. Prevalence increased by- Longer duration of the disease. Prolongation of life, with treatment. If incidence increases. Immigration of new cases. Better reporting of cases. Emigration of healthy people.

20. Prevalence- increased by- 20

21. Prevalence decreased by- Shorter duration of diseases. Improved cure rate. Incidence decreases. Emigration of new cases. Under reporting of cases. Immigration of healthy people.

22. Prevalence decreased by-

23. Mortality indicators-

24. Crude Death Rate. Specific death rate. Case fatality rate. Proportional mortality rate. Survival rate. Standardized death rate. Mortality indicators

25. Number of deaths from all causes, per 1000 estimated mid year population in one year in a given place . No deaths during one year CDR = _________________________ X 1000 Mid year population Crude Death Rate-

26. Cause Specific death rate like disease death rate, Road accident … Age specific- IMR, Child Mortality rate Sex specific death rate – MMR /female Period specific death rate– Death in May Specific death rate-

27. Percentage of particular cases dying during particular disease epidemic. Killing power of disease particularly acute diseases No of deaths due to cholera CFR = ----------------------- X 100 Total No of cholera cases Case fatality rate-

28. Proportion or % of deaths due to particular cause out of total deaths. It measures the disease burden. Under 5, No of deaths below 5 years proportional = -------------------- X 100 mortality rate Total No all of deaths Proportional mortality rate-

29. Percentage of the treated patients remaining alive at the end of 5 years treatment. Yard stick for assessing the standard of therapy in cancer. Survival pts alive at the end of 5 yrs Rate = ---------------------- X 100 Total No of pts treated Survival Rate-

30. CDR can not be useful for comparison. Death rate need to be standardized for comparisons. Standardization can be done by- :adjusting death rate age wise, :also can be done sex/race wise Standardized Death Rate. (Adjusted Death Rate)