NEWS

Health Agencies Adopt New Disease Classification Codes

Lou Fintor

In addition to adopting the new year 2000 U.S. population standard, the nation’s major health statistics agencies are making another major change in the way data is collected and reported by updating the way they have been classifying disease for the last 20 years.

The National Center for Health Statistics is among the first of several agencies and organizations to switch from coding diseases using the International Classification of Diseases and Related Health Problems 9th Revision (ICD-9) to the 10th Revision (ICD-10). This change, which took place over 7 years at a cost of several million dollars, is effective with 1999 mortality data reported by the NCHS.

"In a death certificate, the certifying physician is encouraged to put down as much information as possible regarding the sequence leading up to the immediate cause, including the underlying cause and any contributing causes. But very often we know that the death certificate isn’t filled out properly," said Robert Anderson, Ph.D., lead statistician for the NCHS Mortality Statistics Branch.



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Dr. Robert Anderson

 
The ICD-10 should improve such reporting problems. In addition to containing a set of codes for classifying cause of death, the ICD contains definitions and rules for selecting the underlying and contributing causes of death.

For example, in ICD-9, cardiac arrest is commonly recorded as the cause of death even though HIV infection and HIV-related cancers might be listed as underlying or contributing causes. Under ICD-10 rules, cardiac arrest would be considered an "ill-defined condition" with regard to cause of death when it is associated with cancer and some other diseases.

Similarly, ICD-9 allowed only very specific types of cancers such as certain brain lymphomas to be associated with HIV infection in causing death.

"That rule has now been expanded to include all cancers. The idea is that we now know more about HIV infection and the cancers associated with it and we’re going to better trust the physician’s judgment in those cases and really get at the underlying conditions," Anderson explained.

In a comparison test of the two different versions, Anderson and his colleagues found that, for some causes of death, the coding differences were substantial. Among cancers, the researchers found a very slight increase with the use of ICD-10, indicating that cancer was slightly more likely to be selected as the underlying cause of death than it had been with ICD-9.

In addition to classifying causes of death, the ICD includes internationally accepted coding protocols for the diagnosis of disease or injury and is often also used for administrative purposes such as billing. ICD-10 expands upon previous versions by including codes for occupational and environmental factors, lifestyle. and psychosocial circumstances (e.g., quality of life, etc.). The coding revisions were the result of an international effort and were approved by the World Health Organization in 1990.

"The take-home message is to be careful when comparing data coded using one revision with data coded using an earlier one. There are ways to adjust data from previous years but there are caveats," Anderson said. "You can’t assume data are comparable across revisions because you’ll have discontinuities and in some cases they will be substantial."

NCHS will hold workshops devoted to the ICD-10 transition during its biennial NCHS Data Users Conference on July 15–18 in Washington, D.C. Information on the conference is available through the NCHS Web site (http://www.cdc.gov/nchs/events.htm).



             
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