Measurements in epidemiology
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This document discusses various epidemiological terms used to measure disease frequency and distribution in a population. It defines rate, ratio, and proportion as different ways of comparing two quantities, with rate expressing the occurrence of an event over time, ratio comparing the relative sizes or values of two quantities without a time component, and proportion expressing one quantity as a percentage of the whole. It also defines various epidemiological measures including incidence, prevalence, attack rate, case fatality rate, and different types of mortality rates.
Measurements in epidemiology
- 2. Disease Disease frequency. frequency. Distribution Distribution. determinants. Determinants.
- 3. Mortality. Morbidity. Disability. Presence & absence or distribution of.. Medical needs. Utilization of health services. Demographic variables.
- 5. 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 )
- 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.
- 9. 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 %
- 11. 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)
- 13. Incidence Occurrence of new cases • Prevalence Existence of all new & old cases.
- 14. Prevalence:- how many people in a population currently have the disease (Photograph) Incidence:- how many people are diagnosed each year (Film)
- 15. Cure rate
- 16. New cases
- 17. • The rate at which acute disease is spreading -- used during epidemics & expressed in %. Attack rate • % of exposed persons developing disease after primary case exposure Secondary attack rate
- 18. •Prevalence at any given point of time. • 4% TB cases on 1st April Point prevalence •Prevalence at a given period of time. •Period will be 1year. Period prevalence
- 19. 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. Longer duration of disease Incidence increases. Prolongation of life without cure. 20
- 21. Shorter duration of diseases. Improved cure rate. Incidence decreases. Emigration of new cases. Under reporting of cases. Immigration of healthy people.
- 22. Improved cure rate. Short duration of disease. Incidence decreases
- 24. Crude Death Rate. Specific death rate. Case fatality rate. Proportional mortality rate. Survival rate. Standardized death rate.
- 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
- 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
- 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
- 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
- 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
- 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