CLUSTERING OF
PRIMARY SCLEROSING CHOLANGITIS NEAR TOXIC
WASTE SITES
Presented by Joseph A Odin, M.D., Ph.D.
Assistant Professor of Medicine
Mount Sinai School of Medicine
September 1, 2006
I have nothing to disclose and my presentation will not include discussion of
off-label/investigative use or application of a product or device
September 1, 2006
Pathogenesis of Primary Sclerosing
Cholangitis
Animal
Immune
Environmental
Genetic
Primary
Sclerosing
Cholangitis
Susceptibility
Factors
Dysregulation
Models
September 1, 2006
PSC is prevalence poorly studied
–
Boberg et al, 2001 report the prevalence of PSC
is increased in Scandinavia, but the cause is
unclear.
–
Very difficult to know if prevalence differences
with regard to race, familial incidence,
geography are environmental, societal, or
genetic in origin.
–
In animal models, toxin exposure may induce
PSC-like peri-biliary inflammation and fibrosis.
September 1, 2006
PSC-like Animal Models
–
Direct toxin-mediated biliary injury or murine GVHD
models result in PSC-like lesions.
–
Mdr2(-/-) knockout mice- leakage of bile through disrupted
tight junction leads to a pro-inflammatory/fibrotic
cascade. No known mutations of the human homologue of
Mdr2 (MDR3).
–
Dextran sulfate sodium (DSS) treated CFTR(-/-) KO mice
develop colitis and biliary inflammation.
–
Murine bacterial overgrowth or LPS in immuno-deficient
mice may cause peribiliary inflammation.
Vierling, JM, 2003. Liver Immunology. Review.
September 1, 2006
Autoimmune diseases have been
associated with toxins or xenobiotics
Reprinted from Selmi et al, 2004, Epidemiology and pathogenesis of primary biliary cirrhosis
September 1, 2006
Studies of disease prevalence have shown
geographic variability in PBC
Author(s), year
Geo. clustering
#cases
Yes
34
Sheffield, U.K.
No (seasonal?)
117
northeast England
Triger et al, 1984
Yes
552
Western Europe
none
Borda et al, 1989
Yes
50
Navarra, Spain
none
Danielsson et al,1990
Yes
111
northern Sweden
none
Myszor et al, 1990
No
347
northeast England
Witt-Sullivan et al, 1990
No
225
Ontario, Canada
Yes
770
northeast England
Triger, 1980
Hamlyn et al, 1983
Prince et al, 2001
Site
Factor
water?
(sunlight)
urban
Studies of immigrants suggest environment affects the prevalence of PBC
(Watson et al, 1995 & Anand, 1996)
September 1, 2006
Pathogenesis of
Cholestatic Liver Disease
• Certain toxins are known to cause secondary
sclerosing cholangitis in individuals, but naturally
history may be different than PSC.
• Question: Do unrecognized environmental toxins
trigger PSC or PBC in genetically susceptible
individuals and/or promote disease progression?
September 1, 2006
Possible Approaches to Identifying
Pathologic Toxins
• Epidemiological studies
– Questionnaires regarding exposures
– Prevalence/Cluster analysis and geographic
information systems (GIS) technology
• Further studies in animals exposed to toxins
• Tissue analysis
– Accumulated toxins may be detected in adipose
tissue
– exposure upregulates expression of certain
genes (e.g. MDR, cytochrome p450 genes).
September 1, 2006
What is GIS?
•
Geographic Information Systems (GIS)- “a structural approach to collecting,
archiving, analyzing, manipulating, and displaying data having one or more
spatial components, using a combination of personnel, equipment, computer
software, and organizational procedures.” (National Research Council)
•
“Layers” of spatial data are combined on the same projection or map. Often
unsuspected patterns that escape detection in tabular reports are identified by
projection. (e.g. higher cervical cancer rates in mountainous rural areas and
observation of increased lung tumors in port cities helped establish asbestos
exposure in shipyards as a risk factor).
•
For health studies the combined layers may include a digital photograph of the
area under study, administrative boundaries (e.g. postal codes), environmental
layers (e.g. contaminated areas), facility locations (e.g. hospitals), subject
locations (e.g. patient residences).
•
Each of these spatial layers can be linked by a unique identifier to attribute
data (i.e. clinical data or demographic data). This linkage gives GIS its
analytical power.
September 1, 2006
GIS STEPS
1.
Organize a team of individuals committed to the study including clinicians,
epidemiliogists, data entry specialists and spacial statistician.
2.
Identify study subjects and environmental points of interest and collect
address locations.
3.
Geocoding of address information-conversion to longitude and latitude.
Best if done immediately when address supplied since administrative
boundaries change over time. Collecting all lifetime addresses preferable.
4.
Mapping of prevalence rates in different areas (e.g. postal codes)- adjust
rates to control for potential confounders such as differences in age, gender,
and race distribution among different areas. Confidence levels for each rate
should be included.
5.
Pattern analysis-spatial statistical methods may be helpful in providing a
quantitative answer if not obvious from mapping.
September 1, 2006
Step 1- A team approach
• Interested clinicians- Aftab Ala and
Nancy Bach
• Spatial statistician- Sylvan Wallenstein
• Epidemiologist/data entry specialist“Carmen Stanca”
• Substitute- Joseph Odin
September 1, 2006
Step 2. Recommended guidelines for
identifying subjects
• stringent case inclusion criteria;
• definition of date of disease onset;
• well-defined study period, area and population;
• multiple case finding methods;
• rigorous tracing of all possible cases.
Metcalf, J. & James, O., Semin Liver Dis, 1997
September 1, 2006
Step 3. Address geocoding-converting
addresses into map locations
Software loaded with georeferenced files can automatically
convert appropriately formatted street addresses if available
into specific longitudes and latitudes. Confidentiality must be
maintained however.
Data Quality Issues:
•
Who- best if patient provides address as opposed to insurance data.
•
What- street mail address of residence preferred since offers the smallest point
of reference.
•
When- address at diagnosis usually best for most studies.
An important point is to be consistent and note each factor along with the address
data. Spot checks of data accuracy essential.
September 1, 2006
Available U.S. Liver Disease Clinical
Databases
1.
Individual medical center patient databases.
2.
Independent laboratory records.
3.
Veterans hospitals records.
4.
OPTN (Organ Procurement and Transfer Network) data on
patients listed for liver transplantation.
5.
Nascent international multi-center PSC and PBC registries.
September 1, 2006
OPTN database
• OPTN data limits referral bias as compared to
individual medical centers.
• Demographic information restricted to time of listing
and is not updated.
• Limited subset of patients are listed based on clinical
and non-clinical status.
• Accuracy of data is uncertain.
September 1, 2006
OPTN database
• 102 individuals residing in the NY metropolitan
area with a diagnosis of PSC and 127 individuals
with PBC were listed in the OPTN database
between 1995 and 2003.
September 1, 2006
Long Natural History May Distort
Analysis of Subject Spatial Data
Carcinoma/Death
Progression
(diagnosis)
10-30 yrs?
Normal liver
(disease onset)
Figure adapted from SL Friedman, MSSM
September 1, 2006
Cirrhosis
(listing)
Transplantation
Step 4. Prevalence Data Adjustment
• Demographic data available for all listed PSC
and PBC patients living in New York State
and US census data for individual zip codes
was used to standardize expected
prevalence rates for each New York City zip
(postal) code.
• Observed/stdexpected prevalence rates were
mapped for each zip code with darker colors
indicating higher rates.
• There was no difference in confidence levels
for each value.
September 1, 2006
Calculating and Standardizing Prevalence
Ratios by Zip Code
•
The expected prevalence of patients listed for transplant with PBC or PSC was based
on overall data for UNOS region 9 (New York State and Vermont) from 2000 to 2004.
Female
86%
Male
14%
•
35-49yr
55%
White
86%
Other
5%
Asian
2%
Black
7%
50-64yr
13%
18-34yr
19%
<18yr
0%
65yr+over
13%
Using the 2000 US census data for each zip code, we were thus able to correct for
differences between zip codes with regard to population, age, gender, and race and
standardize the expected prevalence rates (stdE).
September 1, 2006
Step 4. PBC and PSC cluster differently
PSC
PBC
Brooklyn
Manhattan/Bronx
Queens
Staten Island
PBC
September 1, 2006
PSC
Identified Toxic Sites in New York City
This NY website also
provides address
information for each
of these sites, which
is more accurate than
the locations shown
on the map.
Courtesy of the NY DEC
September 1, 2006
Superfund site locations matched best
with high disease prevalence areas
Westchester
Superfund Sites
Boroughs/Counties
New Jersey
Queens
BIGGER
TRIANGLES
Brooklyn
Staten Is.
Adapted from the New York Department of Environment 2004
Superfund Toxic Waste Sites (SFS)
•SFS are sites of public health hazards that have been
designated for immediate remedial action.
•A recent NYC Department of Health study showed an
increased cancer incidence (e.g. breast and lung
cancer) in neighborhoods surrounding NYC SFS.
•Vine et al, 2000, demonstrated deleterious effects on
the immune system of those living near a SFS.
September 1, 2006
Predominant SFS Toxins
•Halogenated solvents
•Heavy Metals e.g. mercury
•PCE 1,1,2,2-tetrachlorethylene
(dry cleaning industry, household
detergents)
•Methyl chloride
•Lacquer
•Solvents
•PCB
Polychlorinated biphenyls
(formely used in hydraulic systems, •Trichloroethane
plasticizer, textile, transformers)
•Xylene
•Tetrachloroethane
September 1, 2006
Hypothesis
The prevalence of PSC and PBC patients listed
for transplantation are increased near Superfund
sites.
September 1, 2006
Step 5. Statistical Analysis
(i) Comparison of prevalence between
“grouped” zip codes with and without SFS
(ii) Comparison of prevalence among boroughs
and SFS density in each borough
(iii) Validated computer analysis (SaTScan):
a) ‘global’ clustering of patients
b) ‘focused’ clustering of patients near SFS
September 1, 2006
Grouped zip code comparison
Each zip code and its adjacent zip codes were considered a group or ‘cluster’
SFS
‘cluster’
SFS
Non-SFS
‘cluster’
September 1, 2006
The median std prevalence ratio of PBC is
significantly higher in SFS clusters
CLUSTERS
WITHOUT
SFS
CLUSTERS
WITH
SFS
P
PBC
0.51
0.94
0.001
PSC
0.28
0.28
0.572
p: significance values for Mann-Whitney U test, 2-tailed Std prev ratio: observed/std expected prevalence
September 1, 2006
Staten Island has the highest prevalence of PBC
& the highest density of SFS
NYC Borough
Std Prev Ratio (rank)
#SFS/100,000/sq mile (rank)
Manhattan
0.66 (5)
0.0211 (5)
Brooklyn
0.91 (3)
0.0411 (4)
Queens
0.88 (4)
0.0561 (2)
Bronx
1.02 (2)
0.0415 (3)
Staten Island
1.54 (1)
0.3150 (1)
September 1, 2006
SaTScan METHOD
TM
•Spatial analysis of the case distribution was conducted using a
cluster detection spatial scan statistic, SaTScan v5.0 adjusting for
the underlying background population.
•Longitudes and latitudes are used
•Global analysis-enter only patient lat & long (zip code center)
•Focused analysis-enter patient and SFS long & lat
Bernoulli and Poisson Models:Kulldorff M. A spatial scan statistic.
Communications in Statistics: Theory and Methods,26:1481-1496,1997
September 1, 2006
PSC clusters
Global and focused cluster analysis of PSC-OLT patients revealed
statistically significant clusters:
•
•
•
one that encompassed all of Staten Island (p=0.050)
a cluster in Nassau County, N.Y. that is near a known SFS
(not shown).
a cluster in Chicago, Illinois. We have started investigating
Chicago given higher numbers of Scandinavians in that
city.
The cluster encompassing Staten Island encircles too many SFS
to identify any specific toxin. The toxin at the Nassau County SFS
included only tetrachloroethylene (PCE). However, as in Staten
Island, a large county-wide active garbage disposal site is also
present in this zip code.
September 1, 2006
Two global clusters identified by SatScan overlap with
Mount Sinai PBC patient clusters
Bronx
2
19
4
New Jersey
Queens
BIGGER TRIANGLES
Brooklyn
2
7
Nassau
Active Solid Waste Site
Superfund Sites
Global Clusters
Mount Sinai Clusters
10
Staten Is.
10
6
7
6
September 1, 2006
10 km
PBC clusters identified by global
analysis were not statistically significant
•SFS were present within 5 out of 6 clusters, but
the clusters were not statistically significant.
September 1, 2006
PBC SFS-focused analysis identified
two statistically significant clusters
• Statistically significant SFS-focused clusters
1. Westchester (10595, 10532) r=2.67 km, p<0.05
2. Staten Is (10312, 10308) r=3.69 km, p=0.05
September 1, 2006
Staten Island SFS Toxins
Number of organic compounds including:
• polychloroethane (PCE), predominately
• Heavy metals e.g. mercury
• Solvents
• Lacquer
Exposure to toxins by aerosol distribution more likely since
groundwater not used in New York City. Toxins may attach to
particulate matter for wider distribution.
September 1, 2006
Fresh Kills - Staten Island
The largest land fill in the world
September 1, 2006
Courtesy of the NYC DEC 2003
Related Animal Studies
• We have begun to study hepatic changes in
mice exposed to particulate matter air
pollutants 5 hours per day/ 5 days per week
for variable periods.
• Early results indicate that exposure for 2+
months significantly increases hepatic
inflammation with a trend towards increased
fibrosis, but cholestatic changes have not
been observed.
• Different mice strains may yield different
results.
September 1, 2006
Summary
•
The overall prevalence of only PBC patients
listed for transplant is increased in zip
codes near NYC SFS.
•
The increased prevalence of PSC and PBC
patients listed for transplantation in Staten
Island corresponds to its high density of
SFS
•
Statistically significant clustering of both
PSC and PBC patients listed for
transplantation occurs near SFS.
September 1, 2006
Limitations
•
Study population
-Cases that never progress beyond early stage disease are excluded.
-Economics may affect both SFS location and who is transplanted.
-Relatively small number of cases limited the study’s power.
-The accuracy of OPTN database is unknown.
•
Using zip codes
-Exact addresses are not available from OPTN.
-Only the zip code at the time of listing for transplant is saved.
•
Migration
-Length of time residing in given zip code prior to listing is unknown.
-In NYC about 50% were living in the same house in 2000 as in 1995.
September 1, 2006
Conclusion
Exposure to toxic wastes may be one of
the environmental factors that plays a role
in the pathogenesis of PSC and PBC
September 1, 2006
ACKNOWLEDGEMENTS
ARTZT FAMILY
PBC FOUNDATION
This work was supported in part by Health Resources and Services Administration contract
231-00-0115. The content is the responsibility of the authors alone and does not necessarily
reflect the views or policies of the Department of Health and Human Services, nor does
mention of trade names, commercial products, or organizations imply endorsement by the
U.S. Government
September 1, 2006
September 1, 2006
GLOBAL SaTScan ANALYSIS
TM
• Most likely PBC clusters
– SI (10312, 10308, 10309) r=3.44 km, p=0.17
FOCUSED SaTScan ANALYSIS
TM
• Most likely PBC clusters
– SI (10312, 10308, 10309) r=3.69 km, p=0.05
September 1, 2006
PBC-Staten Island
MOST
LIKELY
PBC
CLUSTER
September 1, 2006
Large geographical variations in disease (PBC) frequency,
both between and within studies, tantalizingly suggest the
presence of as-yet-unidentified risk factors. This should be
further followed up with new analytical epidemiological
studies.
September 1, 2006
Prevalence May Vary Locally Due to Genetic or
Environmental Factors
1) Genetic predisposition
- Family and twin studies support a link
2) Environmental factors
- Differing water supplies has been linked to local
variability of PBC.
(Triger et al. Br Med J. 1980)
- Cross-reactivity of PBC autoantibodies with
microbial protein epitopes and with autoantigen
modified
by
environmental
chemicals
(xenobiotics)
September 1, 2006
Xenobiotics
• Xenobiotics are foreign chemicals that may alter defined selfproteins, inducing a change in the molecular structure of the
native protein sufficient to induce an immune response
• Association of autoimmune diseases with xenobiotics.
Carpenter D.O et al. Incidence of endocrine disease among
residents of New York areas of concern. Environ Health
Perspect 2001.
• Many xenobiotics are metabolized in the liver
September 1, 2006
PBC in NYC
An increased number of PBC cases noted in Staten Island. Referral
bias?
Manhattan
Queens
September 1, 2006
Bronx
Brooklyn
Staten Island
Staten Island is home to a huge garbage dump and
numerous other toxic sites
September 1, 2006
Potential geoclustering of Mount Sinai
patients (212) with AMA+ PBC
4
19
7
10
10
7
10 km
September 1, 2006