Inci_Pre 222

· A cohort of 10,000 subjects thought to be at increased risk for Breast Cancer (BC), were enrolled in a three-year study in January 1997. At the initial examination on January 1st, 1997, 32 subjects were found to have BC already, 12 of whom died by the end of the study.

· During 1997, 60 cases were subsequently diagnosed, 30 of whom died by the end of the study. Additionally, there were 45 other losses during 1997 for other reasons (deaths from other causes, withdrawal).

· 52 cases were diagnosed in 1998, 9 of whom died, and there were 7 other losses to follow-up during the year.

· 24 cases were diagnosed in 1999, all of whom were still alive at the end of the study. 30 individuals were lost to follow-up for other reasons during 1999.

· Other than the deaths and losses mentioned, the population remained stable during the period, i.e. those enumerated above were the only deaths, refusals or other losses to follow-up.

Use the table below to keep track of deaths and losses for calculations.

Time	initial number (at the beginning of that period)	# persons with BC	fatal cases	lost to follow-up
Start	10,000	32	12	0
1997	9,968
1998
1999
end

Submit the completed worksheet

by EOD (End of Day or 11:59pm) Wednesday, 1/29.

 

HOMEWORK 2 FORMULAS

Baseline prevalence of BC =              #of cases

                                                           total # of persons in the population

 

Incidence =                   # new cases  

                            # susceptible persons in population

 

Incidence with incomplete follow-up =                      # new cases

                                                                                  # susceptible – ½ (losses to follow-up)

 

Incidence density = __total # new cases over time-period_

                                                           # person-years at risk