So which method should we use for the exam and does it apply for incidence and not for prevalence ?

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So which method should we use for the exam and does it apply for incidence and not for prevalence ?

It depends on when you look at the population.

There are two types of Incidence Rates:

The same applies to prevalence, always the denominator is the population at risk, it's just the time you look at them.

First Aid refers to both denominators (of incidence and prevalence) as the population "

(1,000 / 100,000), or

(1,000 / 99,000)?

In a population of 100,000 (without death / migration / etc), of which 1,000 subjects are already HIV(+), and each year an additional 100 patients become infected with HIV, is the period prevalence over 5 years equal to:

(1,500 / 100,000),

(1,500 / 99,000), or

(1,500 / 98,500)?

Thanks for your time and help,

Tig

Cumulative Incidence is the same as just Incidence = at this time, how many cases we have = 100/1000...numerator is just a subgroup of the denominator.

An incidence rate, or simply rate, is defined in terms of number of new cases per observed person-time (rate)

Could you define the acronyms you use (IR)?IR = period time in this case 1 year = 100/1000 (entire population was at risk in that particular period of time)

Cumlative Incidence is the same as just Incidence = at this time, how many cases we have = 100/1000...in this case both are the same

Also, my question was regarding point-prevalence and period-prevalence, not incidence.

Thanks,

Tig

(edit: that is, unless you're responding to the OP instead of me)

TheCould you define the acronyms you use (IR)?

Also, my question was regarding point-prevalence and period-prevalence, not incidence.

Thanks,

Tig

(edit: that is, unless you're responding to the OP instead of me)

The

and btw, if they ask for IR...we should use: new cases per observed person-time (rate)...

There is onlyIt depends on when you look at the population.

There are two types of Incidence Rates:

Incidence Rate:New cases (events) / Population at risk over a period of time, in your example 100/900

Cumulative Incidence Rate:New cases (events) / Population at risk at the beginning of the study, in your example 100/1000

The same applies to prevalence, always the denominator is the population at risk, it's just the time you look at them.

Incidence (aka Cumulative Incidence) = # NEW cases in specified period / # people at risk AT the BEGINNING of the specified period

In INCIDENCE Rate (a "REAL" RATE!), the DENOMINATOR is expressed in "person-time" units (person months, years, etc.)

http://ocw.tufts.edu/Content/1/lecturenotes/194069/194120

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