BioSense

Real-TIME HOSPITAL DATA\
user guide

Application version 2.11

November 2007

Contents

[BioSense 1](#biosense)

[Background Information 1](#background-information)

[Data Types and Pre-processing 1](#data-types-and-pre-processing)

[Data Analysis Steps 2](#data-analysis)

[Access 4](#access)

[BioSense Application: Hospital Data Modules
5](#biosense-application-hospital-data-modules)

[Chief Complaint/Diagnosis 5](#chief-complaintdiagnosis)

[Statistical Anomalies 5](#statistical-anomalies)

[Time Series 5](#time-series)

[Patient List 5](#patient-list)

[Patient Detail 6](#patient-detail)

[Patient Map 6](#patient-map)

[Describe 6](#describe)

[Hospital Census 6](#hospital-census)

[Glossary 7](#glossary)

[Appendix 1: Syndromes 9](#appendix-1-syndromes)

[Appendix 2: ICD-9-CM Codes Grouped to Sub-syndromes
10](#appendix-2-icd-9-cm-codes-grouped-to-sub-syndromes)

[Appendix 3: Sub-syndrome Mapping 12](#appendix-3-sub-syndrome-mapping)

[Sub-syndromes That Map to Syndromes
12](#sub-syndromes-that-map-to-syndromes)

[Sub-syndromes That Do Not Map to Syndromes
12](#sub-syndromes-that-do-not-map-to-syndromes)

**Tables**

[Table 1: W2 Example (Weekday) 2](#__RefHeading___Toc150673269)

[Table 2: W2 Example -- Expected Value and Residual for 8/7
2](#__RefHeading___Toc150673270)

[Table 3: W2 Example (Weekend) 3](#__RefHeading___Toc150673271)

[Table 4: W2 Example -- Expected Value and Residual for 8/6
3](#__RefHeading___Toc150673272)

[Table 5: Example Residual Values for Several Recurrence Interval
Thresholds 4](#__RefHeading___Toc150673273)

# BioSense

## Background Information 

The vision for BioSense is to build a national, real-time
biosurveillance system that can be used for early event detection and
health situational awareness by all levels of public health and the
health care community.

Specifically, BioSense focuses on:

-   **Data transmission**: assuring the secure, timely, routine receipt
    of health data for public health surveillance

-   **Data analysis**: utilizing advanced analytic methods to detect
    events and to enable cities and states to use these methods to
    interpret results in as close to real time as possible

-   **Data reporting**: on a near real-time basis, providing useful
    views of the data, including time-series analysis and geospatial
    displays, for colleagues in state and local health departments as
    well as for Centers for Disease Control and Prevention (CDC) program
    staff

-   **Public Health Response**: providing local data to state and local
    public health officials and supporting their use and interpretation
    of the data for investigations, outbreak responses, and public
    health interventions

## Data Types and Pre-processing

-   **Foundational data types**: patient chief complaint, physician
    diagnosis, supporting patient demographic data, daily hospital
    census.

-   **Additional data types**: emergency department (ED)-specific
    clinical data, microbiology test orders and results, radiology
    orders and results, medication orders.

-   **Patient populations**: ED, hospital inpatient, ambulatory care
    outpatients.

-   **Mapping of International Classification of Diseases, Clinical
    Modification (ICD-9-CM) coded data to 11 syndromes**: data in
    ICD-9-CM form are mapped to 11 syndromes based on a mapping schema
    created in 2003 by a multi-agency working group (Appendix 1).

-   **Mapping of ICD-9-CM coded data to 78 sub-syndromes (Appendix 2)**:
    developed by BioSense medical expert staff, sub-syndromes allow
    surveillance of more granular events than is possible using the 11
    syndromes mentioned above.

-   **Parsing of free-text data to sub-syndromes**: accomplished by a
    text word search and continually improving the keyword search list
    by examining the original free text and its corresponding mapping
    results.

```{=html}
<!-- -->
```
-   Most keywords in the chief complaint to sub-syndrome mapping table
    were derived from the Early Aberration Reporting System (EARS) Text
    String Search method. It contains both English and certain Spanish
    keywords and includes regular terms, misspellings, word fragments,
    and abbreviations. Keywords were modified during the initial
    implementation period.

-   The majority of the keywords in the free-text physician diagnosis to
    sub-syndrome mapping table were derived from terms that appeared in
    ICD-9-CM descriptions.

-   Where appropriate, sub-syndromes are mapped to syndromes (Appendix
    3).

# Data Analysis

## 

## Summary

## Two methods are used, W2count and W2rate. 

## For W2count, the expected value for a weekday is the mean of the previous 7 weekday values, with a 2-day lag. The expected value for a weekend day is the mean of the previous 7 weekend values, with a 2-day lag. The standard deviation is calculated by usual methods. 

## For W2rate, the days on which the expected values are based is the same but the expected value is calculated by accounting for total visits to the facility each day. Since there is no obvious formula to calculate the standard deviation for W2rate, an estimated standard deviation is used. 

## For both W2count and W2rate, a minimum standard deviation of 1 is used. 

## The W2c and W2r statistics are calculated as the number of standard deviation units that the observed value differs from the expected value. 

## Empiric recurrence intervals are calculated based on frequency distributions of the W2c and W2r statistics. 

## For Department of Veterans Affairs and Department of Defense data, 11 holidays are recognized, and these holidays are treated as if they are weekend days for purposes of these calculations. No holidays are used for BioSense Hospital data. 

## 

## Notes

## This document summarizes the data analysis method currently implemented in version 2.11 of the BioSense Application. 

## The method is undergoing continued evaluation and may be modified in future releases. 

## Table 3 with empiric recurrence interval designations will be updated periodically.

## 

## W2count

-   W2 is a modified version of the EARS C2 statistic in which the
    expected value (7-day moving average) is separated into weekdays and
    weekends/holidays.

-   As with C2, the two days immediately preceding the index day (day
    for which an expected value is calculated) are skipped.

-   If the index day is a weekday, ignore the preceding 2 days and
    calculate the mean of the previous 7 weekdays (Table 1).

-   For a weekend day, ignore the preceding 2 days and calculate the
    mean of the previous 7 weekend days (Table 2).

-   At least 4 days of data are required before an expected count is
    calculated.

-   The residual is the observed count minus the expected count.

-   The standard deviation is calculated by the usual formula.

-   If the standard deviation is less than 1, then use 1 as the standard
    deviation.

-   The W2c statistic equals the residual divided by the standard
    deviation.

-   The recurrence interval corresponding to this value of W2c is looked
    up in Table 3.

**W2 Rate**

-   The purpose of this method is to account for the total number of
    visits in addition to the syndrome count. This allows calculation of
    a more accurate expected value. Also, an expected value can be
    calculated when only partial data for a given day is available.

-   For the index day (day for which we calculate an expected value),
    the syndrome count = n and the total visits for the day=d (including
    those binned and not binned to a syndrome).

-   The previous 7 weekday or weekend days (with a 2-day lag) are used
    as for W2count. The 7 observed count values are totaled (=N) and the
    7 total visits values are totaled (=D). (Tables 1-2)

-   The average rate during the 7 day period = N/D.

-   The expected count for the index day = d \*(N/D).

-   At least 4 days of data are required before an expected count is
    calculated.

-   The residual is the observed count minus the expected count.

-   Since there is not a simple formula for the standard deviation, the
    standard deviation is estimated as the mean absolute residual for
    the days upon which W2rate is based.

-   If the standard deviation is less than 1, then use 1 as the standard
    deviation.

-   At least 4 days of expected values are required before an estimated
    standard deviation is calculated.

## Empiric Recurrence Intervals

-   Standard parametric methods (e.g., the normal distribution) do not
    fit this type of data well, especially for extreme results (i.e.,
    high residuals and low p-values). Statistically significant results
    occur far more commonly than would be expected based on the normal
    distribution.

-   The recurrence interval is the reciprocal of the p-value, e.g., if
    p=0.01 is equivalent to a recurrence interval of 100 days.

-   The empiric recurrence intervals are created as follows:

    -   A large number of observations are used to calculate W2c values
        and a frequency distribution of W2c is made.

    -   The recurrence interval for any W2c value is determined from the
        frequency distribution, e.g., the top 1% of W2c values is the
        cutoff value for a recurrence interval of 100 days (Table 3).

    -   A separate distribution and recurrence interval values are made
        for W2r (Table 3).

-   Notice (in Table 3) that a W2c value of 3.5 is approximately
    equivalent to a recurrence interval of 100; this means that in
    historical data we found that the observed count was 3.5 standard
    deviations above the expected value on average every 100 days.

-   The frequency distributions used to calculate the recurrence
    intervals will be updated periodically.

## Table 1: Sample W2Count and W2Rate Calculations (Weekday)

Note: Today is a Wednesday 12/15 and the current syndrome count is 94.

  ----------- --------------- --------- -------- ----------- ---------- ---------- ----------
  Date        Day of Week     Visits    Count    Include     Expected   Expected   Residual
                                                             Value      Value      W2Rate
                                                             W2Count    W2Rate     

  **12/02**   **Thursday**    **329**   **71**   **Yes**     **82.7**   **81.2**   **10.2**

  **12/03**   **Friday**      **327**   **54**   **Yes**     **85.7**   **79.5**   **25.5**

  12/04       Saturday        275       75       No          70.8       64.5       10.5
                                                 (weekend)                         

  12/05       Sunday          313       71       No          70.8       73.4       2.4
                                                 (weekend)                         

  **12/06**   **Monday**      **381**   **86**   **Yes**     **74.9**   **84.4**   **1.6**

  **12/07**   **Tuesday**     **332**   **73**   **Yes**     **74.9**   **73.6**   **0.6**

  **12/08**   **Wednesday**   **325**   **74**   **Yes**     **74.9**   **72**     **2.0**

  **12/09**   **Thursday**    **304**   **72**   **Yes**     **75.9**   **66.5**   **5.5**

  **12/10**   **Friday**      **315**   **64**   **Yes**     **74.6**   **67.3**   **3.3**

  12/11       Saturday        310       64       No          71.5       74.1       10.1
                                                 (weekend)                         

  12/12       Sunday          240       64       No          71.5       57.4       6.6
                                                 (weekend)                         

  12/13       Monday          252       61       No (lag     70.6       53.8       7.2
                                                 day)                              

  12/14       Tuesday         435       117      No (lag     70.6       92.9       24.1
                                                 day)                              

  **12/15**   **Wednesday**   **394**   **94**   ** **       **70.6**   **84.1**   **9.9**
  ----------- --------------- --------- -------- ----------- ---------- ---------- ----------

W2Count

-   Expected value= mean of (71,54,86,73,74,72,64) = 70.6

-   Standard deviation = std dev of (71,54,86,73,74,72,64) = 9.8

-   Residual = 94-70.6 = 23.4

-   W2c = residual/standard deviation = 23.4/9.8 = 2.4

-   Look up recurrence interval for 2.4 in Table 3=30 days

W2Rate

-   N = sum of (71,54,86,73,74,72,64) = 494

-   D = sum of (329,327,381,332,325,304,315) = 2313

-   Expected value = (N/D)\*visits = (494/2313)\*394 = 84.1

-   Estimated standard deviation = mean of (10.2, 25.5, 1.6, 0.6, 2.0,
    5.5, 3.3)=6.9

```{=html}
<!-- -->
```
-   Residual = observed-expected = 94-84.1 = 9.9

-   W2r = residual/est standard deviation = 9.9/6.9 = 1.4

```{=html}
<!-- -->
```
-   Look up recurrence interval for 1.4 in Table 3=10 days

## Table 2: Sample W2Count and W2Rate Calculations (Weekend)

Note: Today is a Sunday 5/20 and the current syndrome count is 81.

## 

  ---------- -------------- --------- -------- ----------- ---------- ---------- ----------
  Date       Day of Week    Visits    Count    Include     Expected   Expected   Residual
                                                           Value      Value      W2Rate
                                                           W2Count    W2Rate     

  **4/22**   **Sunday**     **295**   **69**   **Yes**     **60.1**   **61.2**   **7.8**

  4/23       Monday         368       62       No          68.6       71.9       9.9
                                               (weekday)                         

  4/24       Tuesday        356       63       No          68.6       69.5       6.5
                                               (weekday)                         

  4/25       Wednesday      360       101      No          68.6       70.3       30.7
                                               (weekday)                         

  4/26       Thursday       386       72       No          66.9       72.4       0.4
                                               (weekday)                         

  4/27       Friday         338       56       No          69         65.4       9.4
                                               (weekday)                         

  **4/28**   **Saturday**   **297**   **67**   **Yes**     **59.3**   **61.3**   **5.7**

  **4/29**   **Sunday**     **329**   **60**   **Yes**     **59.3**   **67.9**   **7.9**

  4/30       Monday         403       77       No          69.9       78.7       1.7
                                               (weekday)                         

  5/1        Tuesday        331       59       No          69.9       64.7       5.7
                                               (weekday)                         

  5/2        Wednesday      344       72       No          69.9       67.2       4.8
                                               (weekday)                         

  5/3        Thursday       331       74       No          71.4       64.2       9.8
                                               (weekday)                         

  5/4        Friday         342       65       No          70         65.9       0.9
                                               (weekday)                         

  **5/5**    **Saturday**   **247**   **46**   **Yes**     **64.3**   **52.7**   **6.7**

  **5/6**    **Sunday**     **313**   **60**   **Yes**     **64.3**   **66.7**   **6.7**

  5/7        Monday         398       88       No          67.9       76.4       11.6
                                               (weekday)                         

  5/8        Tuesday        343       73       No          67.9       65.8       7.2
                                               (weekday)                         

  5/9        Wednesday      302       73       No          67.9       58         15
                                               (weekday)                         

  5/10       Thursday       319       67       No          70.1       63         4
                                               (weekday)                         

  5/11       Friday         370       70       No          72.6       75.4       5.4
                                               (weekday)                         

  **5/12**   **Saturday**   **311**   **51**   **Yes**     **60.1**   **62.6**   **11.6**

  **5/13**   **Sunday**     **281**   **63**   **Yes**     **60.1**   **56.6**   **6.4**

  5/14       Monday         433       92       No          72.9       91.8       0.2
                                               (weekday)                         

  5/15       Tuesday        357       69       No          72.9       75.7       6.7
                                               (weekday)                         

  5/16       Wednesday      382       76       No          72.9       81         5
                                               (weekday)                         

  5/17       Thursday       355       77       No          75.4       74.8       2.2
                                               (weekday)                         

  5/18       Friday         374       80       No          76         78.9       1.1
                                               (weekday)                         

  5/19       Saturday       326       52       No (lag     59.4       65.4       13.4
                                               day)                              

  **5/20**   **Sunday**     **335**   **81**   ** **       **59.4**   **67.2**   **13.8**
  ---------- -------------- --------- -------- ----------- ---------- ---------- ----------

##  Table 2 (continued)

W2Count

-   Expected value= mean of (69,67,60,46,60,51,63) = 59.4

-   Standard deviation = std dev of (69,67,60,46,60,51,63) = 8.3

-   Residual = 81-59.4 = 21.6

-   W2c = residual/standard deviation = 21.6/8.3 = 2.6

-   Look up recurrence interval for 2.6 in Table 3=40 days

W2Rate

-   N = sum of (69,67,60,46,60,51,63) = 416

-   D = sum of (295,297,329,247,313,311,281) = 2073

-   Expected value = (N/D)\*visits = (416/2073)\*335 = 67.2

-   Estimated standard deviation = mean of
    (7.8,5.7,7.9,6.7,6.7,11.6,6.4)=7.5

```{=html}
<!-- -->
```
-   Residual = observed-expected = 81-67.2 = 13.8

-   W2r = residual/est standard deviation = 13.8/7.5 = 1.8

```{=html}
<!-- -->
```
-   Look up recurrence interval for 1.8 in Table 3=10 days

##  

## Table 3. Empiric Recurrence Intervals, by Values of W2c and W2r (updated June 13, 2007)

+---------------------------------+------------------------------------+
| **W2c**                         | **W2r**                            |
+---------------------------------+------------------------------------+
| low-1.309=0                     | low-1.336=0                        |
|                                 |                                    |
| 1.309-1.942=10                  | 1.336-1.954=10                     |
|                                 |                                    |
| 1.942-2.302=20                  | 1.954-2.332=20                     |
|                                 |                                    |
| 2.302-2.577=30                  | 2.332-2.594=30                     |
|                                 |                                    |
| 2.577-2.801=40                  | 2.594-2.799=40                     |
|                                 |                                    |
| 2.801-2.984=50                  | 2.799-2.975=50                     |
|                                 |                                    |
| 2.984-3.143=60                  | 2.975-3.116=60                     |
|                                 |                                    |
| 3.143-3.286=70                  | 3.116-3.255=70                     |
|                                 |                                    |
| 3.286-3.429=80                  | 3.255-3.371=80                     |
|                                 |                                    |
| 3.429-3.513=90                  | 3.371-3.477=90                     |
|                                 |                                    |
| 3.513-4.309=100                 | 3.477-4.198=100                    |
|                                 |                                    |
| 4.309-4.857=200                 | 4.198-4.674=200                    |
|                                 |                                    |
| 4.857-5.31=300                  | 4.674-5.017=300                    |
|                                 |                                    |
| 5.31-5.716=400                  | 5.017-5.312=400                    |
|                                 |                                    |
| 5.716-6.053=500                 | 5.312-5.572=500                    |
|                                 |                                    |
| 6.053-6.429=600                 | 5.572-5.814=600                    |
|                                 |                                    |
| 6.429-6.714=700                 | 5.814-6=700                        |
|                                 |                                    |
| 6.714-7=800                     | 6-6.178=800                        |
|                                 |                                    |
| 7-7.429=900                     | 6.178-6.358=900                    |
|                                 |                                    |
| 7.429-7.714=1000                | 6.358-6.533=1000                   |
|                                 |                                    |
| 7.714-8=1100                    | 6.533-6.701=1100                   |
|                                 |                                    |
| 8-8.308=1200                    | 6.701-6.862=1200                   |
|                                 |                                    |
| 8.308-8.571=1300                | 6.862-7=1300                       |
|                                 |                                    |
| 8.571-8.857=1400                | 7-7.108=1400                       |
|                                 |                                    |
| 8.857-9.167=1500                | 7.108-7.257=1500                   |
|                                 |                                    |
| 9.167-9.488=1600                | 7.257-7.413=1600                   |
|                                 |                                    |
| 9.488-9.714=1700                | 7.413-7.545=1700                   |
|                                 |                                    |
| 9.714-10=1800                   | 7.545-7.69=1800                    |
|                                 |                                    |
| 10-10.275=1900                  | 7.69-7.833=1900                    |
|                                 |                                    |
| 10.275-high=2000                | 7.833-high=2000                    |
+---------------------------------+------------------------------------+

## Access

-   BioSense is intended for local, state, and federal public health
    officials' and hospital partners' use. Users could include
    epidemiologists, bioterrorism response coordinators, and hospital
    infection control personnel.

-   Each public health jurisdiction or facility has a BioSense
    Administrator to authorize access to BioSense for appropriate staff
    within their jurisdiction or hospital.

-   Users access BioSense through the CDC Secure Data Network, which
    requires a digital certificate. A user profile is established
    authorizing access to data pertaining to that jurisdiction.

-   Data from a given facility is viewable by personnel at the facility.
    State or metropolitan reporting area (MRA) officials may view data
    for all facilities in their jurisdiction.

# BioSense Application: Hospital Data Modules

## Chief Complaint/Diagnosis

-   *Purpose*: Quick overview of syndrome activity by day for chief
    complaint and diagnosis data stratified by patient class, indicating
    statistically significant syndrome counts.

-   *Display*: Table of syndrome counts for the reason for visit, chief
    complaint, reason for admit, working diagnosis, and final diagnosis
    data (stratified by patient class) for a single day.

-   *Options*: Select Options (analysis method, recurrence interval
    threshold, and time period); Select Data (jurisdiction and/or
    hospital).

-   *Navigation*: To move to the time series grouped by data type and
    stratified by patient class for that syndrome, click a count in the
    table.

## Statistical Anomalies

-   *Purpose*: Identifies anomalies found by automated statistical
    testing.

-   *Display*: Line list of statistical anomalies for syndrome count and
    rate; analyses are performed for individual facilities as well as
    all facilities in a MRA or state. To sort, click a column heading.
    (Note: You can sort up to three columns.)

-   *Options*: Select Options (analysis method, recurrence interval
    threshold, and time period; Select Data (jurisdiction and/or
    hospital).

-   *Navigation*: To move to the time series grouped by data type and
    stratified by patient class for that syndrome, click an anomaly in
    the line list.

## Time Series

-   *Purpose*: Displays trends and statistical anomalies over time for a
    disease indicator.

-   *Display*: Graph of number of counts and/or rate per 1,000 visits by
    day. Statistical anomalies are indicated by stars on the graph
    lines. Each Monday is indicated by a vertical line, and each holiday
    is shaded blue. The default time series is grouped by data type and
    stratified by patient class (although other options are available
    within Select Data). To select a particular data type and patient
    class, either click on the graph line of interest or make changes to
    the Select Data options. Beneath the graph is a table for each day;
    it includes date, day of the week, count, rate, total records, and
    links to the Patient Map and Patient List.

-   *Options*: Select Options (analysis method, recurrence interval
    threshold, graph lines (counts, rates, total visits and their
    corresponding expected values, and graph line color), and time
    period; Select Data (jurisdiction and/or hospital, data source, data
    type, event type, event, race, age, gender, group by, and stratify
    by).

-   *Navigation*: To move to the Patient List, which displays a line
    list of patient visits comprising the point on the graph, click the
    desired graph point. To move to the Patient Map or Patient List for
    the selected day, click the corresponding links to the map and
    patient list in the table beneath the graph.

## Patient List

-   *Purpose*: Examines epidemiologic patterns for clinical and
    demographic data for a group of patient visits.

-   *Display*: Line list of patients' information including location,
    demographic, and clinical data. To sort, click a column heading.
    (Note: You can sort up to three columns.) To save the Patient List
    to Excel, click on the disk icon above the table on the right side.
    To navigate between pages of the Patient List, click to move forward
    or backward using the options available above the table on the right
    side.

-   *Options*: None.

-   *Navigation*: To move to Patient Detail, click the desired row
    within the Patient List.

## Patient Detail

-   *Purpose*: Provides all detailed data for an individual patient.

-   *Display*: Detailed information organized by facility, patient,
    visit, and clinical data type (chief complaints, diagnoses,
    procedures, ED clinical, radiology, and pharmacy.).

-   *Options*: None.

-   *Navigation*: None.

## 

## Patient Map

-   *Purpose*: Displays disease indicator geographic distribution by zip
    code of patient residence.

-   *Display*: Map indicating numbers of patients by zip code.

-   *Options*: Select Options (Map Layers (Highways, State Borders,
    County Borders, Zip Borders, and their corresponding labels) and
    number of levels to which patient visit counts will be categorized).

-   *Navigation*: To view geographic distributions for previous days,
    use the date navigation tool. To zoom in and out, use the zoom tool.

## Describe

-   *Purpose*: Provides basic descriptive statistics for a group of
    patient visits.

-   *Display*: Patient distributions (counts and percents) by Hospital
    Facility, Age Group, Gender, Race, Hour of Day, Patient County,
    Hospital Patient Class by Data Type, Sub-syndrome, and Syndrome in a
    series of thumbnail graphs.

-   *Options*: Select Options (time period, graph bar color); Select
    Data (jurisdiction and/or hospital, data source, data type, event
    type, event, race, age, and gender).

-   *Navigation*: None.

## Hospital Census

-   *Purpose*: Provides daily inpatient hospital census data.

-   *Display*: Hospital-level census data includes occupancy rate,
    admission count, discharge count, and death count. Unit-level census
    data includes occupied beds and available beds.

-   *Options*: Select Options (analysis method, recurrence interval
    threshold, and time period); Select Data (jurisdiction and/or
    hospital).

-   *Navigation*: None.

# Glossary

-   **Analysis Visit ID**: Created by BioSense to provide a consistent
    definition of a visit regardless of how a visit is defined by a
    given hospital. Combines patient visits, if they occur within 24
    hours of each other. Does not contain personally identifiable
    information.

-   **Anomaly Location**: Location of an anomaly identified by
    statistical algorithms. Example: Single facility, State/MRA
    (combining data for all facilities within a state or MRA).

-   **Anomaly**: See "Statistical Anomaly."

-   **Artifact**: An anomaly that can be explained by factors other than
    true disease, e.g., miscoding of data at the source, receipt of
    duplicated data, or a new influx of data.

-   **BioIntelligence Center**: BioSense personnel who monitor the
    BioSense application, track data anomalies, support state and local
    BioSense users, and assist with troubleshooting and improvements.

-   **BioSense Patient ID**: Uniquely distinguishes a patient across all
    visits to a single facility or across all visits to a healthcare
    system when a common patient identification system is used. Can be
    used by the healthcare facility to associate BioSense patient data
    to the patient's medical record. The Patient ID, displayed in
    BioSense, includes a string of numbers separated by a carat (\^).
    The Patient ID portion of this identifier is on the left side of the
    carat, and an identifier for the integrator at the facility or
    hospital system sending data to CDC is on the right side of the
    carat. Does not contain personally identifiable information.
    Example: 12345\^1234.

-   **BioSense Visit ID**: Used to uniquely distinguish a patient visit
    based on the healthcare facility account identifier. Created to
    reflect the visit as defined by the healthcare facility. Does not
    contain personally identifiable information.

-   **Disease Indicators**: Variables evaluated for a statistical
    increase in temporal trend\
    (e.g., 11 syndromes or 78 sub-syndromes).

-   **Early Event Detection**: Recognition of an outbreak or other
    public health emergency at as early a stage as possible. Emphasis is
    placed on detecting the very first upswing of the epidemic curve.

-   **Electronic Biosurveillance**: The use of information in computer
    databases to perform public health surveillance.

-   **Expected Value**: The number of disease indicator events expected
    during a given time period, usually an extrapolation of the number
    of such events that have occurred in the past. Example: The W2
    statistic uses the mean count of the previous 7 weekday or
    weekend/holiday days (with a 2-day lag) as the Expected Value.

-   **Geo Area**: Geographic area basis upon which jurisdictional public
    health access to BioSense is granted. Example: state, region, or
    MRA.

-   **Observed Value**: Actual number of disease indicator events during
    a time period. Examples: number of patient visits meeting the
    respiratory syndrome; number of positive blood cultures.

-   **Observed/Expected (Relative Risk)**: Ratio of the Observed Value
    divided by the Expected Value. A measure of the magnitude of disease
    activity. If the Expected Value equals zero, the BioSense
    application indicates this ratio is undefined. An alternative method
    adds one (1) to both the Observed and the Expected to complete the
    calculation.

-   **Outbreak**: An epidemic, i.e., the occurrence, in a community or
    region, of cases of an illness, specific health-related behavior, or
    other health-related events clearly in excess of normal expectancy.

-   **Patient Class**: The setting for a patient visit. Examples:
    Emergency Department, Ambulatory Care, Inpatient.

-   **PHIN**: Public Health Information Network. At the core of PHIN and
    BioSense are commonly accepted health data standards including
    Health Level Seven (HL7), Systematised Nomenclature of Medicine
    (SNOMED), and Logical Observations Identifiers, Names, Codes
    (LOINC). For more detail, refer to the PHIN standards website:
    (<http://www.cdc.gov/phin>).

-   **Rate (per thousand visits)**: Number of events divided by total
    number of patient visits multiplied by 1,000.

-   **Recurrence Interval**: Expected time (days, years) of surveillance
    needed for one such event of at least the observed magnitude to
    occur. This is a user-defined setting to increase or decrease the
    sensitivity of statistical algorithms. For example, if the
    recurrence interval is 100, an event of at least this magnitude
    would be expected every 100 days.

-   **Residual**: Observed -- Expected; measures the difference between
    the Expected count (calculated, for example, by the W2 method) and
    the Observed count. A high residual may indicate a data anomaly.

-   **Situational Awareness**: Literally, the ability to know what's
    going on; accomplished by monitoring the extent of disease or
    disease indicators over time and geographically, especially in an
    emergency context. Emphasis is placed on monitoring after the
    initial upswing of the epidemic curve.

-   **Statistical Anomaly**: Something different, abnormal, or unusual
    in data found by statistical analysis. Statistical significance does
    not necessarily imply epidemiologic or clinical significance.

-   **Sub-syndrome**: Set of 78 disease indicators, developed for use in
    BioSense, to allow for surveillance at a more granular level than
    would tracking the 11 syndromes (Appendices 2-3). Examples:
    abdominal pain, allergy.

-   **Syndromes**: Set of 11 disease indicators developed by a
    multi-agency working group to represent prodromes of certain
    potentially bioterrorism-related diseases (Appendix 1).

-   **Syndromic Surveillance**: Performing surveillance for syndromes
    (as opposed to confirmed or suspect cases of disease); commonly
    performed to facilitate early outbreak detection and situational
    awareness.

# Appendix 1: Syndromes 

Data in the BioSense application are organized into the following 11
syndromes.

-   Botulism-like

-   Fever

-   Gastrointestinal

-   Hemorrhagic Illness

-   Localized Cutaneous Lesion

-   Lymphadenitis

-   Neurological

-   Rash

-   Respiratory

-   Severe Illness/Death

-   Specific Infection

Definitions of these syndrome categories and lists of ICD-9-CM codes
included in each syndrome can be found at:
<http://www.bt.cdc.gov/surveillance/syndromedef/index.asp>. ICD-9 codes
are divided into three categories based on overall association with a
syndrome or a specific disease and by observed frequency of code usage
in three clinical data sources (representing discharge diagnoses for
outpatient visits and emergency department visits). The following
categories within syndrome groups were defined:

-   **Category 1** -- Codes that reflect general symptoms of the
    syndrome group including codes for bioterrorism diseases of highest
    concern or diseases highly approximating them.

-   **Category 2** -- Codes that might normally be placed in the
    syndrome group but for which daily volume could overwhelm or
    otherwise detract from the signal generated from the Category 1 code
    set.

-   **Category 3** -- Codes that reflect specific diagnoses that fit
    into the syndrome category but that occur infrequently or have very
    few counts. These codes may be excluded to simplify syndrome
    category code sets.

\*Specific Infection contains all Category 3 codes, while Category 1 and
Category 2 codes are placed into their respective syndrome groups.

# Appendix 2: ICD-9-CM Codes Grouped to Sub-syndromes

  -----------------------------------------------------------------------
  **ICD-9-CM Codes**          **Sub-syndrome**
  --------------------------- -------------------------------------------
  789.0, 789.6                Abdominal pain

  995.3                       Allergy

  780.0                       Alteration of consciousness

  280-285                     Anemia

  783.0                       Anorexia

  493                         Asthma

  E906                        Bites, animal

  466, 490                    Bronchitis and bronchiolitis

  940-949                     Burns

  986                         Carbon monoxide poisoning

  426-427, 785.0              Cardiac dysrhythmias

  430-438                     Cerebrovascular disease

  786.5                       Chest pain

  320-326                     CNS, inflammatory disease

  286                         Coagulation defects

  780.01                      Coma

  780.3                       Convulsions

  491-492                     COPD (Chronic Obstructive Pulmonary
                              Disease)

  786.2                       Cough

  782.5, 799.0                Cyanosis and hypoxemia

  798                         Death

  276.5                       Dehydration

  250                         Diabetes mellitus

  787.91                      Diarrhea

  780.4                       Dizziness

  787.2                       Dysphagia

  786.0                       Dyspnea

  782.3                       Edema

  E880-E888                   Falls

  780.6                       Fever

  003.0, 003.9, 005           Food poisoning

  800-839                     Fractures and dislocation

  781.2, 781.3                Gait abnormality

  578                         Gastrointestinal hemorrhage

  784.0                       Headache

  410-414                     Heart disease, ischemic

  E900                        Heat, excessive

  786.3                       Hemoptysis

  459.0                       Hemorrhage

  401, 405                    Hypertension

  458                         Hypotension

  487                         Influenza-like illness

  959                         Injury, nos (not otherwise specified)

  910.4, 910.5, 911.4, 911.5, Insect bites
  912.4, 912.5, 913.4, 913.5, 
  914.4, 914.5, 915.4, 915.5, 
  916.4, 916.5, 917.4, 917.5, 
  919.4, 919.5                

  009                         Intestinal infections, ill-defined

  782.4                       Jaundice

  683, 785.6                  Lymphadenopathy

  780.7                       Malaise and fatigue

  781.6                       Meningismus

  290-319                     Mental disorders

  346                         Migraine

  E810-E819                   Motor vehicle traffic accidents

  729.1                       Myalgia

  787.0                       Nausea and vomiting

  140-239                     Neoplasms

  782.0                       Numbness

  870-879                     Open wound

  381-382                     Otitis media

  342, 344                    Paralysis

  368.13                      Photophobia

  511                         Pleurisy

  480-486, 513                Pneumonia and lung abscess

  960-979                     Poisoning by medicines

  630-677                     Pregnancy, childbirth, puerperium
                              complications

  287, 782.7                  Purpura and petechia

  782.1                       Rash

  518.8, 799.1                Respiratory failure

  079.6, 466.11, 480.1        RSV (respiratory syncytial virus)

  038, 790.7                  Septicemia and bacteremia

  785.5                       Shock

  680, 681, 682, 684, 686     Skin infection

  438.1, 784.5                Speech disturbance

  840-848                     Sprains and strains

  780.2                       Syncope and collapse

  460-465                     Upper respiratory infections

  590, 595, 599.0             Urinary tract infection

  079.99                      Viral infection, unspecified

  369                         Visual impairment
  -----------------------------------------------------------------------

# Appendix 3: Sub-syndrome Mapping

## Sub-syndromes That Map to Syndromes 

-   **Botulism-like**: Paralysis; Speech disturbance; Dysphagia

-   **Fever**: Fever; Septicemia and bacteremia; Viral infection,
    unspecified

-   **Gastrointestinal**: Abdominal pain; Anorexia; Diarrhea; Food
    poisoning; Intestinal infections, ill-defined; Nausea and vomiting

-   **Hemorrhagic Illness**: Coagulation defects; Gastrointestinal
    hemorrhage; Hemorrhage; Purpura and petechia

-   **Localized Cutaneous lesion**: Insect bites; Skin infection

-   **Lymphadenitis**: Lymphadenopathy

-   **Neurological**: Alteration of consciousness; Central nervous
    system (CNS) inflammatory disease; Convulsions; Gait abnormality;
    Headache; Meningismus; Photophobia

-   **Respiratory**: Asthma; Bronchitis and bronchiolitis; Chest pain;
    Cough; Cyanosis and hypoxemia; Dyspnea; Influenza-like illness;
    Otitis media; Pleurisy; Pneumonia and lung abscess; Respiratory
    failure; RSV; Upper respiratory infections; Hemoptysis

-   **Rash**: Rash

-   **Severe Illness and Death**: Coma; Death; Shock

## Sub-syndromes That Do Not Map to Syndromes 

-   **Injury**: Bites, animal; Burns; Carbon monoxide poisoning; Falls;
    Fractures and dislocation; Heat, excessive; Injury, not otherwise
    specified (nos); Motor vehicle traffic accidents; Open wound;
    Poisoning by medicines; Sprains and strains

-   **Chronic Disease**: Cardiac dysrhythmias; Cerebrovascular disease;
    Chronic obstructive pulmonary disease (COPD); Diabetes mellitus;
    Heart disease, ischemic; Hypertension; Neoplasms

-   **Other**: Allergy; Anemia; Dehydration; Dizziness; Edema;
    Hypotension; Jaundice; Malaise and fatigue; Mental disorders;
    Migraine; Myalgia; Numbness; Pregnancy, childbirth, puerperium
    complications; Syncope and collapse; Urinary tract infection; Visual
    impairment