# Presentation: 186994

## ICD-9 Codes in CDC BioSense Neurological Syndrome

- Haobo Ma, Jerome Tokars, Roseanne English
- Centers for Disease Control and Prevention, Atlanta, GA

## BioSense

- Electronic biosurveillance system to enhance national preparedness for
- Early event detection and health situational awareness
- Bioterrorism attacks
- Naturally-occurring diseases
- Safety net for public health

## Current Data Sources

- Department of Defense (DoD) outpatient medical treatment facilities (n=355)
- ICD-9 diagnosis codes
- CPT procedure codes
- Veterans Affairs (VA) outpatient medical centers and clinics (n=849)
- ICD-9 diagnosis codes
- CPT procedure codes
- Laboratory Corporation of America
- Test orders
- BioWatch
- BioSense RT

## BioSense Syndromes

- ICD-9 codes binned to 11 syndromes
- Neurological syndrome
- Designed to detect acute neurological infection of central nervous system
- Classified as
- Category 1 (general symptoms and diseases of highest concern)
- Category 2 (high-volume codes might detract from the category 1 signal)
- Combined for analysis
- Possible neurological diseases in bioterrorism attack
- Western equine encephalitis, Eastern equine encephalitis; Venezuelan equine fever, Taiga encephalitis, Central European encephalitis, Tick-borne encephalitis

## Methods

- Study period: 01/01/2004 to 12/31/2005
- Demographics (age, gender)
- Data distribution among states
- Frequencies and seasonal patterns of ICD-9 codes composing neurological syndrome
- Differences in code use in Veterans Affairs (VA) vs. Department of Defense (DoD)

## Results

- 1,193,853 visits had ICD-9 codes for neurological syndrome
- 35% from Department of Defense (DoD)
- 65% from Veterans Affairs (VA)
- Median age
- DoD: 29
- VA: 56
- Gender
- DoD: 40% male
- VA:  90% male

## Neurological Syndrome Visits, by State, 2004 - 2005

## Neurological Group ICD-9 Codes, by Category

| Category 1 * | Category 2 ** |
| --- | --- |
| 047.9 Viral meningitis, NOS 
049.9 Viral encephalitis NOS
322.9 Meningitis, unspecified 
323.9 Unspecified cause of encephalitis
348.30 Encephalopathy, unspecified
047.8 Other specified viral meningitis
048 Other enterovirus diseases of central nervous system
049.0 Lymphocytic choriomeningitis 
320.9 Meningitis due to unspecified bacterium 
321.2 Meningitis due to viruses NEC
322.0 Nonpyogenic meningitis
322.1 Eosinophilic meningitis 
323.8 Other causes of encephalitis
781.6 Meningismus | 293.0 Acute delirium
293.1 Subacute delirium
307.81 Tension headache
780.39 Other convulsions
780.02 Transient alteration of awareness
780.09 Other alteration of consciousness
784.0 Headache
784.3 Aphasia |

- *Category 1 ( **1.4%** )		**Category 2  ( **98.6% )**

## Category 1 Code Frequencies, by Data Source

| Codes | DoD |  | VA |  |
| --- | --- | --- | --- | --- |
|  | n | % | n | % |
| 047.9 Viral meningitis, NOS  | 1491 | 21.3 | 523 | 5.3 |
| 049.9 Viral encephalitis NOS  | 146 | 2.1 | 72 | 0.1 |
| 322.9 Meningitis, unspecified  | 2022 | 28.8 | 3106 | 31.2 |
| 323.9 Unspecified cause of encephalitis  | 983 | 14.0 | 3369 | 33.9 |
| 348.30 Encephalopathy, unspecified | 1343 | 19.1 | 2315 | 23.3 |
| Other codes | 979 | 14.7 | 569 | 6.7 |

## 047.9 Unspecified Viral Meningitis, DoD vs. VA

- 047.9 Unspecified Viral Meningitis, DoD vs. VA

## 322.9 Unspecified Meningitis, DoD vs. VA

## Category 2 Code Frequencies, by Data Source

| Codes | DoD |  | VA |  |
| --- | --- | --- | --- | --- |
|  | n | % | n | % |
| 307.81 Tension headache | 48113 | 11.5 | 17868 | 2.4 |
| 780.09 Other alteration of consciousness | 6648 | 1.6 | 10851 | 1.4 |
| 780.39 Other convulsions | 37347 | 9.0 | 319619 | 42.0 |
| 784.0 Headache | 317900 | 76.2 | 376263 | 49.4 |
| 784.3 Aphasia | 3715 | 0.9 | 31605 | 4.2 |
| Other codes | 3445 | 0.8 | 5075 | 0.7 |

## Neurological Syndrome - Summary

- VA and DoD outpatient visits differ demographically
- Most commonly used ICD-9 codes differ in VA vs. DoD
- Category 1 codes much less frequent than category 2 codes
- Most frequent category 1 ICD-9 codes showed seasonal patterns in DoD

## Meningitis-associated hospitalization by etiologic category and month of discharge, NHDS, United States, 1988-1999

- Khetsuriani N, Quiroz ES, Holman RC, Anderson LJ. Viral meningitis-associated hospitalizations in the United States, 1988-1999. Neuroepidemiology. 2003 Nov-Dec;22(6):345-52.

## Limitations

- Uncertain accuracy in ICD-9 code assignment
- Individual patients may contribute multiple visits

## BioSense RT

- Initiative within BioSense Project that emphasizes acquisition of clinically rich data in real time from hospitals in major US cities
- Neurological subsyndromes
- Alteration of consciousness, CNS inflammatory disease, convulsions, gait abnormality, headache, meningismus, photophobia
- Planned BioSense new interface will give users ability to create own ICD-9 code groups

## Conclusions

- Analyses of individual codes, or groups of codes, may be useful
- Category 2 codes may mask variations in category 1 codes
- Split neurological syndrome into high vs. low frequent codes
- BioSense data may be a supplemental source for tracking diseases
- Unspecified viral meningitis ICD-9 code in DoD
- Influenza, injuries, and Respiratory Syncytial Virus

## Acknowledgements

- Stephen Kralovic, Gary Roselle, John F Quinn
- Nino Khetsuriani, Larry Anderson, Mark A Pallansch, Steve Oberste
- Laura R Hall, Paul McMurray