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Salud y medicina

Following is my Seminar presentation on Standerdization

Kunal ModakSeguir

- 1. PRESENTED BY: DR. KUNAL GUIDED BY: DR. ABHAY MUDEY STANDERDIZATION
- 2. What is standardization? The development and application of a standard for a particular measures or type of component or range of measurements or proportions or rates. The process by which you derive a summary figure to compare health outcomes of groups. The process can be used for mortality or morbidity data. 8/11/2015 2
- 3. 8/11/2015 3 What distinguishes standardization of rates from other stratified methods of controlling for confounding, is use of an external standard as the basis for comparison.
- 4. Basic Measurement 8/11/2015 4 o Ratio o Proportion o Rates- o Case fatality rate o Mortality rates(age specific/cause specific)
- 5. Crude vs. standerdized PREFER REJECT Uniform Localized Adapted Line shows likelihood of correction
- 6. Standardization Of Rates 8/11/2015 6 Used to reduce distortion in comparisons between crude areas Also referred to as adjusting rates
- 7. Crude rate 8/11/2015 7 Advantages Actual Summary rates Easy calculation for international comparisons Disadvantages Since population vary in composition (e.g., age) differences in crude rates difficult to interpret
- 8. Specific Rate 8/11/2015 8 Advantages Homogenous subgroups Detailed rates useful for public health and Epidemiological aims Disadvantages Cumbersome to compare subgroups of two or more populations
- 9. Adjusted Rates 8/11/2015 9 Advantages Summary statement Differences in group composition “removed” allows unbiased comparison Disadvantages Fictional rates Absolute magnitude dependent on standard population chosen Opposing trends in subgroup masked
- 10. Direct Adjusted Rates 8/11/2015 10 Requires a standard population, to which the estimated age-specific rates can be applied Choice of the standard population may affect the magnitude of the age-adjusted rates, but not the ranking of the population
- 11. Direct Adjusted rates 8/11/2015 11 Multiply standard population by age- specific rates for populations A and B to determine the standardized rates Compare standardized rates
- 12. Population, deaths, death rate by community & by age 8/11/2015 12 Community A Community B Age (year) Population Deaths Death Rate (per 1000) Population Deaths Death Rate (per 1000) Under 1 1,000 15 15.0 5,000 100 20.0 1 – 14 3,000 3 1.0 20,000 35 1.0 15 – 34 6,000 6 1.0 35,000 35 1.0 35 – 54 13,000 52 4.0 17,000 85 5.0 55 – 64 7,000 105 15.0 8,000 160 20.0 Over 64 20,000 1,600 80.0 15,000 1,350 90.0 All ages 50,000 1,781 35.6 100,000 1,740 17.4
- 13. Standard Population by Age and Age- Specific Death Rates 8/11/2015 13 Age (years) Standard populatio n Death rate in A (per 1,000) Expected deaths at A’s rate Death rate in B (per 1,000) Expected deaths at B’s rate Under 1 6,000 15.0 90 20.0 120.0 1 – 14 23,000 1.0 23 0.5 11.5 15 – 34 41,000 1.0 41 1.0 41.0 35 – 54 30,000 4.0 120 5.0 150.0 55 – 64 15,000 15.0 225 20.0 300.0 Over 64 35,000 80.0 2,800 90.0 3,150 Total 150,000 35,6 3,299 17.4 3,772.5 Age – adjusted death rate (per 1000) 22.0 25.0
- 14. Indirect Adjustment of Rates 8/11/2015 14 Used if age-specific rates cannot be estimated Mirror image of the direct method
- 15. Indirect Adjestment Of Rates 8/11/2015 15 Based on applying the age-specific rates of the standard population to the population of interest to determine the number of “expected” deaths. Standardized Mortality ratio
- 16. Standardized Mortality Ratio 8/11/2015 16 Total observed deaths in a population ----------------------- Total expected deaths in a population
- 17. Standardization Examples o Direct Method requires Age-specific rates in the sample population The age of each case The population-at-risk for each age group in the sample Age structure (percentage of cases in each age group) of a standard population 8/11/2015 17
- 18. Indirect Standardization Instead of a standard population structure, you utilize a standard rate to adjust your sample Indirect standardization does not require that you know the stratum- specific rates of your cases The summary measure is the SMR or standardized mortality/morbidity ratio SMR = Observed X 100 Expected 8/11/2015 18
- 19. Standardize Mortality Rate Expect a Healthy worker effect Occupational studies should have SMRs < 100 Workers tend to be healthier than the general population which comprises both healthy and unhealthy individuals You cannot compare SMRs between studies -- only to the standard population 8/11/2015 19
- 20. Standardization: Age Adjustment (cont.) Indirect method requires Age structure of the sample population at risk Total cases in the sample population (not ages of cases) Age-specific rates for a standard population 8/11/2015 20
- 21. Age Standerdization Occurrence of disease in one area may appear to be higher than in another because: population structures are different one area is older than another Standardisation used to adjust for the effects of age on mortality rates or other rates Direct or Indirect Involves the calculation of numbers of expected events which are then compared with numbers of observed events. 8/11/2015 21
- 22. Example of London and Camden 8/11/2015 22
- 23. The problem… The crude rates are not comparable because the age structure of the populations are different What would the expected number of deaths be in London and Camden if the age structures were the identical? This is DIRECT STANDARDISATION called DIRECT STANDARDISED RATES What would the expected number of deaths be in London and Camden if the age specific rates were identical? This is INDIRECT STANDARDISATION called STANDARDISED MORTALITY RATIO 8/11/2015 23
- 24. Direct standardisation – method 1. Decide which standard population to use – EUROPEAN STANDARD POPULATION 2. Calculate expected deaths if both London and Camden had the same population structure as the European standard. 3. Express as a rate per 1,000 or 100,000 population 8/11/2015 24
- 25. Direct standardisation Example of London and Camden 8/11/2015 25
- 26. Interpretation of SMRs SMR < 100 : lower rate than expected SMR = 100 : Expected/standard rate SMR > 100 : higher rate than expected An SMR of 180 represents a mortality rate that is 80% higher than expected. 8/11/2015 26
- 27. Standardised mortality ratio 2005-07 8/11/2015 27
- 28. Which Method To Use? If want to compare several population groups or several time periods use DIRECT as with INDIRECT can only compare each population group to the standard. INDIRECT is useful to determine if disease incidence is high or low in one area only. If age specific rates for the population groups are not available or unreliable use INDIRECT. If it is a rare event and therefore number of deaths in population groups is small (e.g. ward level CHD deaths) use INDIRECT. 8/11/2015 28
- 29. Issues in the use of standardization Standardized rates are used for the comparison of two or more populations; they represent a weighted average of the age specific rates taken from a 'standard population' and are not actual rates. The direct method of standardization requires that the age-specific rates for all populations being studied are available and that a standard population is defined. 8/11/2015 29
- 30. Continued.... The indirect method of standardization requires the total number of cases The ratio of two directly standardized rates is called the Comparative Incidence Ratio or Comparative Mortality Ratio. The ratio of two indirectly standardized rates is called the Standardized Incidence Ratio or the Standardized Mortality Ratio. 8/11/2015 30
- 31. Continued.... Indirect standardization is more appropriate for use in studies with small numbers or when the rates are unstable. As the choice of a standard population will affect the comparison between populations, it should always be stated clearly which standard population has been applied. 8/11/2015 31
- 32. Continued.... Standardization may be used to adjust for the effects of a variety of confounding factors including age, sex, race or socio-economic status. 8/11/2015 32
- 33. Pros Cons Able to compare different areas with each other. Can look at trends through time. (Only if ALL use the same standard population) Need local data for all age bands Rare diseases may have no events in specific age bands so age specific rates may be unavailable May need to merge events from different years or combine age bands Pros and Cons of DSRs 8/11/2015 33
- 34. Pros Cons Can use where diseases are rare Don’t need local event information for all age groups Just need total number of observed and expected counts Cannot compare SMRs with each other unless population structures are identical Cannot look at trends through time Pros and cons of SMRs 8/11/2015 34
- 35. Summery Standardisation can be use in many areas Although we’ve looked at mortality, the technique can be applied in other ways: Hospital admissions Prevalence/incidence of disease Prescriptions Etc ● One type of rate is not necessarily more important than another. Which you choose depends on the information sought. 8/11/2015 35
- 36. Continued.... Standardized rates provide a kind of “snapshot” of the overall risk of disease or death, which can be compared across populations. Standardization of rates can be difficult to understand and is explained in several different ways depending on the literature source. 8/11/2015 36
- 37. Aknowledgement Dr. Minakshi Khapre Dr. Abhishek Ingole Dr. Pramita Mutonde All the PG’S in the department. 8/11/2015 37
- 38. References 1. Heinekens CH, Burring JE. Epidemiology in Medicine. Lippincott Williams & Wilkins, 1987. 2. Farmer, R. Lawperson, R. 2004. Lecture notes in Epidemiology and Public Health Medicine pp 67-68. Blackwell Publishing. Text Book of Community Medicine (Fourth Edition)- By. Dr. Kulkarni, Dr. P.P. Doke, Dr. J.P Baride, Dr. P.Y. Mulay Basic Concept & Methodology for the Health Sciences (Ninth Edition)- By- Wayan W. Daniel Community Medicine with recent Advances- By- A.H. Suryakantha Park’s Text Book of Preventive Social Medicine (23rd Edition)- By_ Dr. K.Park 8/11/2015 38