Q&A: Is ’backward mapping’ from ICD-10-CM/PCS to ICD-9-CM appropriate?

Q: Our facility is considering having our coders and CDI specialists “go–live” with ICD-10-CM/PCS on July 1, in order to practice to help off-set the impact of ICD-10. The system will would then code backwards into ICD-9-CM for billing. Is this “backward mapping” method appropriate?

A: The biggest issue is how your ICD-10-CM/PCS coding will be “translated” into ICD-9-CM for claims processing until CMS accepts ICD-10-CM/PCS codes to process claims. If your system is coding backward code, the resulting code will likely be based on GEMs, which CMS discourages.

CMS specifically states the GEMS are not for coding purposes, but rather to help build coding databases. Backward mapping—going from an ICD-10-CM/PCS code to an ICD-9-CM code—could be problematic, and could result in assigning many nonspecific codes, which may have reimbursement ramifications. The GEM mappings were not intended to be used for coding purposes, but rather to help build coding databases.

Many codes have a “one to many” ratio, resulting in either a nonspecific code or, in some cases, a “no map” option. Ideally, we would like to think if we convert documentation to ICD-10-CM/PCS that it would automatically backward map to the correct ICD-9-CM code, but it may not.

For example, if the documentation states “severe persistent intrinsic asthma,” the ICD-10-CM assigned code would be to J45.50 (severe persistent asthma, uncomplicated), because the term “intrinsic” in ICD-10-CM/PCS is now an included term not previously factored into category selection in ICD-9-CM. So, if you backwards map the code J45.50, it will translate to 493.00 or 493.10 in ICD-9-CM.

Unfortunately, this does not translate to a direct match: 493.00 is for extrinsic asthma and 493.10 is for intrinsic asthma. The ICD-10-CM/PCS code translates to two possible ICD-9-CM codes, and only one can be chosen. But it has to backward map to both because the code for severe persistent asthma does not identify extrinsic or intrinsic in ICD-9-CM.

Most organizations are dual-coding–coding in both ICD-9-CM so their claims can be reimbursed appropriately, and in ICD-10-CM/PCS so they can practice the new code set and identify improvement opportunities. However, not all organizations have software that can “hold” both code sets simultaneously. If your software allows you to hold both codes, even though it is time consuming, the best suggestion is to native code in both ICD-9-CM and ICD-10-CM/PCS. If you rely merely on the backwards mapping, it may not achieve the desired result. The systems are not identical, and very few codes have exact maps.

Editor’s Note: Cheryl Ericson, MS, RN, CCDS, CDIP, AHIMA Approved ICD-10-CM/PCS Trainer, Associate Director for Education at ACDIS and CDI Education Director, and Shannon E. McCall, RHIA, CCS, CCS-P, CPC, CPC-I, CEMC, CCDS Director of HIM and Coding at HCPro in Danvers, Massachusetts contributed to this response. For more information regarding upcoming Boot Camp dates and locations visit www.hcprobootcamps.com/courses/10040/location-dates.