Mapping Influenza-Like Illness (ILI) Using Physician Claims Data

Larry SvensonPublic Health Surveillance and

Environmental Health Branch

Public Health Division

Public Health Surveillance

“Public health surveillance is the ongoing, systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those who need to know…A surveillance system includes the functional capacity for data collection, analysis and dissemination…”

- CDC Surveillance Update, 1988

Importance of Influenza Surveillance Rapidity with which epidemics evolve Widespread morbidity and the seriousness of

the complications (notably pneumonia) The rate at which influenza viruses show both

shifts and drifts in their surface proteins

Age-Standardized Influenza Mortality, Alberta 1986 to 2005

Year

19861987

19881989

19901991

19921993

19941995

19961997

19981999

20002001

20022003

20042005

Ag

e-S

tan

dar

diz

ed M

ort

alit

y R

ate

per

100

,000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Number of Albertans Diagnosed with Influenza, 1983 to 2006

Year

Ca

ses

(n

)

0

2500

5000

7500

10000

12500

15000

17500

20000

22500

25000

27500

30000

32500

35000

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Annual Number of Cases of Influenza Treated in Emergency Departments, 1984 to 2006

Year

19841985

19861987

19881989

19901991

19921993

19941995

19961997

19981999

20002001

20022003

20042005

2006

Cas

es

(n)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

Approach

Background

Physicians submit electronic claims for reimbursement for services provided

This information contains up to three diagnostic codes in addition to other information

82% of all physician services data is available for analysis within two weeks

90% of all physician services data is available for analysis within four weeks

Method

The Alberta Health and Wellness data warehouse is updated on a weekly basis

Data is extracted from the fee-for-service database for all physician services regardless of diagnosis

Data on all emergency department claims are also extracted

The data are organized by person, place, and time for each diagnosis

Diagnostic Groups Included Acute Respiratory Tract Infections (ICD-9-CM

460-464) Other Upper Respiratory Tract Infections

(ICD-9-CM 462, 465, 470-478) Bronchitis (ICD-9-CM 466, 490) Pneumonia (ICD-9-CM 480-486) Acute Otitis Media (ICD-9-CM 382.0, 382.4,

382.9) Streptococcal Sore Throat (ICD-9-CM 034) Influenza (ICD-9-CM 487)

Measure Computed

Case counts by week for each diagnosis for: General practitioner offices Emergency departments

Number of influenza cases per physician Number of influenza cases per 100 patients

seen Age- and sex-specific rates

AllTransactions

Registry

Filter

Diagnoses(460-466, 470-478,

480-487, 490)

UniqueILI Services

AllUniqueServices

Filter

ServiceCubes

AGE SPECIFIC RATES, FEMALE & MALE ACCUTE RESPIRATORY ILLNESS (cubic spline=SM25)

01NOV2004 to 24OCT2005

SOURCE TABLE: workarea.crili_ag_sx

FEMALE MALE

RA

TE

0.050.060.070.080.090.100.110.120.130.140.150.160.170.180.190.200.210.220.230.240.250.260.270.280.290.300.310.320.330.340.350.360.370.380.390.400.410.42

AGE GROUP

00to04 05to09 09to14 15to19 20to24 25to29 30to34 35to39 40to44 45to49 50to54 55to59 60to64 65to69 70to74 75to79 80to84 85plus

CLINICALLY DIAGNOSED INFLUENZA: REGION 06

Time period(e.g., 23Nov04 to

23NOV05)

Selectepisodes

Graphs

Tables EpisodeDefinition

ILI ServiceCubes

ILI EpisodeCubes

Maps

StorageStorage

Storage

Number of Influenza Cases Diagnosed by General Practitioners by Week

Number of Clinically Diagnosed Influenza Cases by General Practitioner,

2005/06 and 2006/07 by Week Alberta .

Weeks

40414243444546474849505152 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930313233343536373839

Ca

ses

0

200

400

600

800

1000

1200

1400

2005/20062006/2007

Age-Specific Rate per 100,000 Population – Influenza (Week Ending February 24, 2007)

Percent Influenza Like Illness – Week Ending February 24, 2007

Percent Influenza Like Illness – Emergency Department

Number of Cases of Respiratory Disorders Diagnosed by General Practitioners by Week

Number of Cases of Respiratory Disorders Diagnosed in Emergency Departments by Week

Geographic Distribution of Influenza – Week 5 to Week

9, 2007

2007 – Week 5

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

2007 – Week 6

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

2007 – Week 7

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

2007 – Week 8

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

2007 – Week 9

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

All-Cause Mortality

Number of Deaths (all causes) by Week

Age-Specific Mortality Rate per 100,000 Population (Week 9)

Geographic Distribution of Mortality Rates – Week 5

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

Geographic Distribution of Mortality Rates – Week 6

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

Geographic Distribution of Mortality Rates – Week 7

Geographic Distribution of Mortality Rates – Week 8

Geographic Distribution of Mortality Rates – Week 9

Edmonton

Calgary

Higher

Probably Higher

Average

Probably Lower

Lower

No cases

Next Steps

Repackage the information to fit within Pandemic Influenza planning and monitoring

Utilize the internet for dissemination to a wider audience

Expand to include other disorders as part of syndromic surveillance

“Good surveillance does not necessarily ensure the making of right decisions, but it reduces the chances of wrong ones.”

- A. D. Langmuir

N Engl J Med 1963; 268: 182-191