Transcript Counting WhalesCounting a Disease

Rates are the hallmark for
epidemiology for they form the basis
of comparisons between population
groups
Rose and Barker,1986
“The Price of Health, like that
of liberty, is Eternal Vigilance”
“An improvement in the treatment of disease, and
any addition to medical science, will tend
ultimately to the diminution of human suffering;
but the registration of the causes of death is
calculated to exercise a still more direct influence
upon public health. Diseases are more easily
prevented than cured, and the first step to their
prevention is the discovery of their exciting causes
by numerical facts and measure the intensity of
their influence.”
William Farr, 1839
Exclusively Rural Areas
Doctors sent to rural areas
Leper census, 1836 (5), 1845 (8), 1845 (11)
Leprosy viewed as inheritable--sexual isolation,
hospitals, prohibiting marriage
No experience in setting up the registration
Local Health officer
Royal Decree
Problems with local registration
(definition, deadlines, incomplete)
Circular letters
Chief Medical Officer travelling to each
area
Over diagnosis initially (acne, scabies)
Low prevalence areas, disease overlooked
Undercount, Undercount, Undercount
Isolation: Areas where isolation practiced,
most rapid decline in disease
Definitions
Prevention
Reducing the incidence of disease (primary
prevention)
Reducing the prevalence of disease (second.
prevent.)
Control
Ongoing operations or programs aimed at reducing
the incidence and/or prevalence of disease
Last, Dictionary of Epidemiology
General Motors sold 2,542,455
Automobiles World Wide
99 Billion Sold
NCDs
What is the incidence
of Diabetes?
What is the incidence
of CHD?
What is the incidence
of Cancer?
Nobody Knows
Surveillance
Health Dept.
Continuous analysis, interpretation,
and feedback of systematically
collected data, generalized using
methods distinguished by their
practicality, uniformity, and
rapidity, rather than by accuracy or
completeness. Last, Dictionary of Epidemiology
CDC Comes in
120
80
Total Cases
Reported Cases
60
Typical Pattern
40
20
Month
TV says Flu
12
11
10
9
8
7
6
5
4
3
2
0
1
Number of Cases
100
Registry
Academia
…the term register is applied to the file
of data concerning all cases of a
particular disease or health -relevant
condition in a defined population such
that the cases can be related to a
population base. Last, Dictionary of Epidemiology
Disease Monitoring Systems
Surveillance Registries
Disease
Infectious
Chronic
Coverage
Large
Small
Cost
Low
High
Speed
Fast
Slow
Ascertainment Low/Variable
Presumed
High
Allegheny County Type I Diabetes Registry
1.
2.
3.
4.
5.
Diagnosed between 1/1/65 and 12/31/99
Age at onset <20
Diagnosis of Diabetes
On Insulin at time of Hospital Discharge
Resident of Allegheny County at Diagnosis
Allegheny County Type I Diabetes Registry
16
/100,000
Undercount
/100,000
Registry
WHO DiaMond Project
Epidemiologists
Counting Disease
Prairie Chicken
Biostatistics
1 2 3 4
5 6 7 8 9
Capture
Mark
RECAPTURE
Capture-Recapture
Sample 1
Sample 2
N=
(M+1)(n+1)
-1
(m+1)
M m
n
N = Estimate of Number
M =Number in First Sample
n = Number in Second Sample
m =Number of “marked” items
in Second Sample
Var(N)=
(M+1)(n+1)(M-m)(n-m)
2
(m+1) (m+2)
In Common
Capture-Recapture
Methods
Long history of use in Demography
i.e. US Census
The standard for estimating the
abundance or shortage of wildlife
populations
Fish
Disease
Net
List
Tag
Name/
Identifier
Recapture Duplicate
Lower Extremity
Amputation Study
Adolescent Injuries
Sports injuries
Dog Bites
Optimal “Lists” to identify
cases
Independent
Reasonable ascertainment
Inexpensive
Comparison of “lists to gold standard”
CR to Registry
Good monitoring does not necessarily
ensure the making of right decisions, but it
reduces the risk of wrong ones.
Languimer, 1963
Public Health
Cancer Incidence in Middle East
Good monitoring does not necessarily
ensure the making of right decisions, but it
reduces the risk of wrong ones.
Languimer, 1963
Porpoises can teach
Epidemiologists how to count