Transcript Counting Chronic Hepatitis B cases in York Region

Counting Chronic Hepatitis B
cases in York Region:
Denis Heng
York Region Community and Health Services
APHEO Conference - “Explaining the Miracle: Statistics and
October 15, 2007
Analysis in Public Health”
Infectious Diseases
Surveillance Unit (IDSU)
• Component of the Infectious Diseases
Control Division, Community and Health
Services.
• Tasked with coordinating surveillance and
school immunization programs with the
objective of controlling infectious
diseases within York Region.
"Greetings!
I am the Count.
Do you know
why they call
me the
Count?
Because I love
to count
things!"
Hepatitis B
• Globally, it is estimated that:
– ~2 billion have been infected with hepatitis B
virus
– >350 million have chronic (lifelong) infections
• Highly endemic (>8% prevalence) in certain
areas of the world
– East and Southeast Asia, Sub-Saharan Africa
• A reportable disease in Ontario
Estimating HBV Carriers in Canada
Canadian
Population
Hepatitis B
carriers
29,839,030
598,103
Immigrants
18.4%
54.7%
Aboriginals
3.3%
6.5%
78.3%
38.8%
N=
Canadian-born
Source: Sherman et al. Can J Gastro 2007; 21(Suppl C)
Background
• York Region Health Services converted from the
Reportable Disease Information System (RDIS) to
integrated Public Health Information System
(iPHIS) in June 2005
Example of Duplicate Record:
• Client A lives in Toronto and is diagnosed with
hepatitis B in 1993; Toronto Public Health
creates an RDIS record with an episode date
of 1993;
Background
Example of Duplicate Record (cont’d):
• Client A moves to York Region in 2003 and a
subsequent hepatitis B lab slip is forwarded to
York Region Health Services as a result of
regular lab testing. York Region creates an
RDIS record with an episode date of 2003;
• July 2005: RDIS conversion to iPHIS – Client
A now has two iPHIS entries for hepatitis B –
one 1993 entry attributed to Toronto and one
2003 entry attributed to York Region.
Purpose
800
Number of Confirmed Cases
• Examine the
extent to which
York Region
chronic hepatitis B
incidence data is
affected by
duplicate records
resulting from the
merger of
Ontario’s 37 RDIS
platforms.
700
600
500
400
300
200
100
0
2005
2006
Pre-validation
750
465
Post-validation
?
?
Methods
• Cognos line lists were created
– Includes all iPHIS entries that have York
Region as either the Responsible or Diagnosing
Health Unit
• A manual name search on each of these
individual records was performed to
identify any duplicate entries in iPHIS.
0
D '06
N '06
O '06
S '06
A '06
J '06
J '06
M '06
A '06
M '06
F '06
J '06
D '05
N '05
O '05
S '05
A '05
J '05
J '05
M '05
A '05
M '05
F '05
J '05
Number of Confirmed Cases
Number of Confirmed Chronic Hepatitis B cases in
York Region, Pre- and Post-Validation (2005-2006)
80
70
60
50
40
30
20
10
0
D '06
N '06
O '06
70
S '06
80
A '06
J '06
J '06
M '06
A '06
M '06
F '06
J '06
D '05
N '05
O '05
S '05
A '05
J '05
J '05
M '05
A '05
M '05
F '05
J '05
Number of Confirmed Cases
Number of Confirmed Chronic Hepatitis B cases in
York Region, Pre- and Post-Validation (2005-2006)
Pre-Validation
Post-Validation
60
50
40
30
20
10
0
35
Pre-Validation
30
Post-Validation
D '06
N '06
O '06
S '06
A '06
J '06
J '06
M '06
A '06
M '06
F '06
J '06
D '05
N '05
O '05
S '05
A '05
J '05
J '05
M '05
A '05
M '05
F '05
J '05
Number of Confirmed Cases
Number of Confirmed Chronic Hepatitis C cases in
York Region, Pre- and Post-Validation (2005-2006)
25
20
15
10
5
Ratio of pre-validated to post-validated counts
of chronic hepatitis B cases in York Region by
month (2005-2006)
2005
2006
January
1.66
1.04
February
2.29
1.09
March
2.32
1.32
April
2.16
1.18
May
1.97
1.08
June
1.67
1.05
July
1.65
1.00
August
1.68
1.03
September
1.76
1.09
October
1.79
1.03
November
1.38
1.07
December
1.26
1.09
Percentage of Duplicate Records by
Health Unit in 2005
• 368 duplicate
records identified
in 2005 (339 clients)
Toronto
84%
• ~8% had more
than one duplicate
record
York
Other
2%
Ottawa
2%
Peel
Region
2%
Region
10%
Reasons for Duplication – post RDIS
• Clients using multiple common names that were
not recorded during the initial investigation.
– E.g., Record 1 is listed as Ricky Chan; Record 2 is listed
as Sai-Kee Chan;
• Inversion of month/day fields when recording
date of birth from source documents.
– E.g., First DOB is 1977-07-06; Second DOB is 197706-07; and
• Typographic errors in the spelling of family
names due to partially legible source documents.
– E.g., John Paur VS John Paun
Conclusion
•
Incidence counts of
chronic hepatitis B cases
in York Region before
2006 are significantly
overestimated due to
duplicate records
produced in RDIS
As such, the 2005
counts validated as part
of this study, and 2006
disease counts reflect
the most accurate data
available at this time for
estimating the burden of
disease of new chronic
hepatitis B cases in York
Region.
Number of Confirmed Cases
•
800
700
600
500
400
300
200
100
0
2005
2006
Pre-validation
750
465
Post-validation
428
427
Implications
• Overestimate of provincial counts
• Affect counts in other health units
– GTA health units
• Are other reportable diseases overestimated?
Acknowledgements
• Hepatitis B/C Team – York Region Health
Services
– Case investigators
– Administrative staff
• All other YRHS staff that have
contributed to this project
Questions?