Case Fatality Rate (CFR)•Formula:•# of case patientsx 100# of cases reported•It answers what percent of people diagnosed as having a certain disease die within a certain time after diagnosis.•If 25 of every 100 (25 ÷100=.25 x 100 =25%) persons diagnosed with lung cancer die in 5 years the CFR is 25%. •The 5 year survival rate is 1 - .25 = (.75 ) or 75 %33
Let’s resume.. VNA Case Study•Refer to page 123•Since the epidemic began, 107,980 cases of HIV/AIDS have been diagnosed in Florida.•Nearly half (48%) have occurred in African American people.•What information does Lindsay need to understand the scope of the problem in the two counties?•Refer to page 124 •There are 2,150 people living with HIV/AIDS•What is the crude rate of the HIV/AIDS burden in these two counties?35
Incidence Rate•The number of newcases at a particular point or period of time•Calculated in a similar way to mortality ratesExample: Flu in VA•From Jan 1 –Dec 31 2014 there were 500 cases of influenza dx in Virginia; Population is 8,000,000.# of newly diagnosed cases in a certain time period divided by # at risk of disease in population X 100,000500 ÷8,000,000= .0000625 X 100,000 = 6.25 new cases of influenza per 100,000 in 201436
VNA Case Study•Page 126•Lindsay finds that 384 new cases of HIV infection were dx in the 2 counties within the last year. •What is the incidence rate?•Contrast this incidence rate with:•The crude rate calculated on page 124 and •The incidence rate in the US 83.7 new HIV infections per 100,000 in one year. 37
Attack Rates•The attack rate (AR) is a special incidence rate used in investigations of disease outbreaks. Often used with food borne illness outbreaks and during an epidemic •Number of people at risk who develop a certain illness/Total number of people at risk.•Example: Age groups with high ARs are at increase risk of diseaseNumber of people at risk who develop the diseaseTotal number of people at risk X 100 =
Your turn: the picnic problemAttack rate calculation•226 people ate chicken salad at the picnic•176 people developed acute GI symptoms•What is the attack rate?
Prevalence•Prevalence- all(old + new) the people with a given health condition at a particular point or period of time•it’s a proportion of the population that has a certain disease at one point in time•Influenced by 2 factors•Number of people with condition in past•Duration of illness•It is expressed as a percent•Explain:•Period •Point Prevalence40
A way to think about prevalence:41
Prevalence•Number of existing cases of a disease at one point in time ÷ total number of population X 100.•In NJ there were 10,000 people with CHF and the population was 700,000.•10,000 ÷ 700,000 X 100 = 1.4 % of the population has CHF•So the prevalence of CHF in NJ is 1.4%42
Now your turn…..•Calculate the prevalence of diabetes in Virginia.•Number of people with diabetes in 2014 were 531,000•The population is 8,326,000.