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Assessing Disease Frequency

ملتقى الطب الوقائي
موضوع مغلق
  #1  
قديم 02-23-2011, 07:17 PM
الصورة الرمزية الكفاح
 


الكفاح will become famous soon enoughالكفاح will become famous soon enough


Why should we be concerned with monitoring disease(s)?
Disease Control and Prevention

Good monitoring does not necessarily
ensure the making of right decisions,
but it reduces the risk of wrong ones.
Languimer, 1963
There are several decisions regarding Disease monitoring
What level of resources should be allocated to disease monitoring?
What outcomes do we want to achieve?
What benefits are obtained from these items and to whom do the benefits accrue?
Can the counting methods be readily accepted into the community?
Approaches Towards Monitoring Disease and Injury
Death Certificates
Population Surveys
Surveillance
Registries
Screening

Surveillance:
Systematic, regular ascertainment of incidence using methods distinguished by their practicality, uniformity, and frequently their rapidity, rather than by complete accuracy
Let’s spend some more time talking about each of the major systems for identifying injuries. The primary means to identify injuries is to establish a surveillance system.
What is a surveillance system? John Last has defined surveillance as the regular assessment of disease or injuries, with a common method, and often an approach that is simplistic rather than complex. One of the key words here is regular assessment. Injury monitoring, such as that with death certificates, is set up to evaluate injuries over time. With common methods, this allows a researcher to examine changes over time in these events.
.
Types of Surveillance
Active
Passive
Active Surveillance
the collection of data on a disease by regular outreach. Designated medical personnel are called at regular intervals to collect information on the new cases of disease
Active surveillance involves the regular monitoring of surveillance sites by designated persons. These persons often call up a site to gather information on injury events that happened in the previous month or week. One example of this process would be the surveillance of injuries from domestic violence in emergency departments. Research personnel would contact emergency departments on a regular interval to identify injury events from domestic violence. As no data sources routinely identify domestic violence injuries, this type of active surveillance is necessary to identify the incidence of domestic violence events.
.
Passive Surveillance
data generated without contact by the agency carrying out the surveillance. Reportable diseases fall under this type of surveillance
More commonly surveillance systems are passive. By definition, researchers or health department personnel do not go out into the community to find cases. Rather, they develop instruments that persons in the community have to send into them (e.g. death certificates) as a means of identifying events. Reportable diseases such as AIDS and malaria, etc. are monitored in this fashion.
Laboratories, physicians, and hospitals have to report these events to the health department when they identify a case at their institution.
In some states, spinal cord injuries are a reportable condition and are followed with passive surveillance.
.
••
So you have identified the Frequency of disease in a given area….
What do you do with it?
Epidemiology is a Science of Rates
death rates
disability rates
hospitalization rates
incidence rates
prevalence rates
Epidemiology is a science based upon rates. Incidence and prevalence rates provide information on the importance of a disease or injury in a defined population. Understanding how many injuries occur (the absolute number) provides only one part of the puzzle; the numerator. The second piece is the population in which they occur; the denominator. As we will see, the denominator is a very important factor in defining the significance of a problem.
Effective injury control is based upon an understanding of injury rates; i.e. how many injuries occur within a given population.
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من مواضيعي : الكفاح
  رقم المشاركة : [ 2 ]
قديم 02-26-2011, 03:04 PM
صحي جديد
 

القيراطي will become famous soon enough
افتراضي

مشكوووره الاخت كفاااح بصراحة معلومات قيمة
بس ودي تنزلي مقال عن rates and ration في المراكز الرعاية والمستشفيات
القيراطي غير متواجد حالياً  
  رقم المشاركة : [ 3 ]
قديم 02-26-2011, 10:21 PM
صحي نشط
 

تحسين الآداء will become famous soon enough
افتراضي Rates, Ratio and Proportions

Rates, Ratio and Proportions
Ratio

A
ratio is made of 2 elements, the numerator “a” and the denominator “b”.
a/b
عددالمواليد الذكور\ عدد المواليد الإناث

Proportions
A proportion is a ratio where the numerator “a” is part of the
denominator
•عددالمواليد الذكور\ عددالمواليد الذكور+عدد المواليد الاناث
Rates
Rate is a proportion that is specified in time, thus a rate for disease would be

Measures of Mortality
Indices of Mortality
Crude Death Rates =
# death in during the year\
Averagepopulation size




Disease specific
Death Rates =
# death due to spc disease\
Population at risk

Age specific
Death Rates =
# death among persons in a given age group\
Population size in given age group

Case Fatality Rate =
# death due to spc disease\
Total number of people with disease

Proportionate Mortality=

# death due to spc disease\
Total number of death from all diseases

Maternal Mortality Rate=


# death due to puerperal causes\
Total number of live births


Measures of Morbidity
Indices of Morbidity
Incidence Rate =
# NEW cases of disease\
population at Risk of disease

يضرب الناتج في
Over a period of time



Prevalence Rate =
EXISITING cases of disease\
TOTAL population


At a given point in time


Indices of Morbidity
More on Incident and Prevalent Cases
Incident cases are the new cases that emerges in a defined population during a specific period of time
Prevalent cases are cases that were present for all or part of a specific period of time:
Point prevalence: The period of time is short Period prevalence: the period of time is longer
Example
Measures of Fertility
Indices of fertility
Crude Birth Rate =
# live births\Total Population


Indices of fertility
General Fertility Rate=
# live births\
Total # of women in childbearing age

Adjusting Death Rates
The need for Adjusted Rates
When comparing the crude death rates between Panama and Sweden, one would expect that Sweden would have lower crude death Rates.
However the numbers show a reverse pattern where Panama CDR = 9.37 per 1000 and
Sweden CDR = 10.20 per 1000
Lets look at the age distribution
The Age Pyramid
Adjusted Rates
It is clear that Sweden has a larger % of its population in the older group.
And we know that the age specific death rates of older people is higher than the younger one.
Adjusted Rates
From the previous tables it is clear that:
The Age distribution between the 2 countries is different
Within each age group, the Age Spc DR for Panama is higher
Nonetheless the CDR for panama is lower
Thus we need to account for the age distribution: Adjust for Age
Adjusted Rates
There are 2 ways to adjust for age:
The Direct Method
The Indirect Method
The Direct Method requires the knowledge of the Age SDR for each country
Then a Standard Age Distribution is selected, and applied to Both
Direct Method of Adjustment
Lets suppose the age distribution of Panama was the same as Sweden. Meaning we will select the age distribution of Sweden as the standard one
Then we apply to Age SDR using the new distribution, get the total number of deaths, and then calculate the Adjusted DR
Direct Method of Adjustment
Sweden CDR = 10.2
Panama CDR = 9.37
After Adjustment the new A
Adjusted DR = 13.1
Clearly the Death Rate in Panama is higher
Indirect Method of Adjustment
As we said earlier, the indirect method is used when the age specific death rates is not known.
Let’s suppose we did not know the Age Specific death rates for Panama.
Then we would used the age specific death rates of Sweden for panama, and get the expected numbers of Death
Survival and Life Expectancy
Life expectancy
In the following example we will show how the Expected life expectancy is calculated
The life table shows the life expectancy at each age interval
Life table
Lets do the example on Excel
Sources of Data
Source of data
There are different sources of data on mortality and morbidity in the community.
Each source bear its advantage and disadvantages.
1.Census
2.Vital Statistics
3.Morbidity data
4.Linked health records
Census
Is the periodic counts or enumeration of a population.
In the states every 10 years there is a complete census.
Census assess a wide range of factors: age ***, marital status, race….
The information available in census help to quantify the number of people living in an area, or a subgroup such as woman, elderly, infants…
This information is essential in calculating rate, and other mortality and morbidity statistics
Vital Statistics
Ongoing recording of the vital events of a population: birth, death, marriage, divorce.
The important one for Epi are death, featal death and birth.
1. Death Certificates: provides info on the dead person such as age *** race occupation, also can be used to quantify frequency of death. It also provide cause of death, used for calculating specific death rates (how else would we know the leading cause of death).
The physician must assign a cause of death from a list of tabulated codes in the ICD (Injuries and Causes of Death).
Vital Statistics
2. Certificate of Live Birth: information provide: ***, weight at birth, mother and father age, gestational age, parents education, congenital abnormalities, previous pregnancies…..
3. Certificate of Fetal Death: definition by WHO is all fetal death regardless of gestational age, nonetheless the practice in the states not to record unless it has 20 weeks of gestational age (almost 4 months)
Morbidity Data
There are organizations that deals with collecting information of occurrence of specific disease. One major organization in the states is the CDC (Center for Disease Control and Prevention).
1. Notifiable disease: Depending on countries there are a list of disease that are required to be reported to the officials, the idea is to keep track of the prevalence of disease to make sure if an epidemic occur to be able to stop it as quickly as possible. Also some disease are dangerous and contagious. (through reporting the States were able to figure out about the Anthrax, Mad Cow disease, AIDS)
Morbidity Data
4 disease are required to be reported internationally: Cholera, Plague, Smallpox, and Yellow fever.
many countries report cases of cancer and AIDS.
2. Hospital records: are also rich with data
3. Private Clinics
4. Disease registries.
5. Special surveys: National health surveys includes the Health Interview survey, Health and Nutrition examination survey,
من مواضيع : تحسين الآداء
تحسين الآداء غير متواجد حالياً  
  رقم المشاركة : [ 5 ]
قديم 03-30-2012, 06:50 PM
المشرف العام

الصورة الرمزية نسائم
 

نسائم will become famous soon enoughنسائم will become famous soon enough
افتراضي

السلام عليكم ورحمة الله وبركاته


يعطيك العافية
بارك الله فيك وشكراً لك
من مواضيع : نسائم
نسائم غير متواجد حالياً  
  رقم المشاركة : [ 6 ]
قديم 04-02-2012, 07:03 PM
افتراضي



عليكم السلام ورحمة الله وبركاته

الله يعافيك ويسلمك

الف شكر لك على مرورك العطر

وجزاك الله كل خير على هذه الدعوات الطيبة

من مواضيع : الكفاح
الكفاح غير متواجد حالياً  
  رقم المشاركة : [ 8 ]
قديم 04-12-2012, 02:09 AM
افتراضي



الله يعافيك ويسلمك

الف شكر لك على مرورك العطر

وجزاك الله كل خير على هذه الدعوات الطيبة

من مواضيع : الكفاح
الكفاح غير متواجد حالياً  
موضوع مغلق

مواقع النشر (المفضلة)

الكلمات الدليلية (Tags)
assessing, disease, frequency


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