One of the challenges in ICD-9 is teaching the difference between coding for adverse effects and poisonings. You have to understand the difference between the two, and you have to also understand the coding differences. I often tell my students to make sure they write the definitions of adverse effects and poisonings right near the table of drugs and chemicals in their ICD-9 Manuals, as well as the coding guidelines for each of them so that the information is right where they need it. For ICD-10, the table of drugs and chemicals as well as the guidelines will undergo revisions, so we will have to adjust our thinking as well.
When coding for adverse effects in ICD-9, you must code first the “reaction” followed by the E code (external causes) identifying the substance that caused the adverse reaction. This E code comes from the therapeutic column. This is different from coding a poisoning, for which we first report the poisoning code followed by the reaction and then the E code, which identifies the substance as well as how the patient was poisoned (e.g., accident, suicide, assault, or undetermined).
In the ICD-10 draft manual, the columns have changed. Now the “therapeutic column” has been deleted from the table, and a new column for “adverse effect” has been added. The poisoning column no longer exists but has been replaced by several columns that read: “poisoning accidental (unintentional)”, “poisoning Intentional/self-inflicted”, “poisoning assault”, and “poisoning undetermined.” There has also been a new column added to identify “underdosing,” which seems to be an increasing problem. Because the table of drugs and chemicals looks different, what does this mean for the coding of these two types of conditions?
For adverse effects, ICD-10 guidelines state, “Codes in categories T36-T65 are combination codes that include the substances related to the adverse effects, poisonings, toxic effects and underdosing, as well as the external cause. No additional external cause code is required for poisonings, toxic effects, adverse effects and underdosing codes.” According to the guidelines, the T36-T65 code would be the first listed code. You would also report the code(s) that specify the “reaction” or as ICD-10 calls it “the nature of the adverse effect, poisoning, or toxic effect.”
There are further guidelines:
- Do not code directly from the table; always refer back to the tabular list.
- Use as many codes as necessary to completely describe all drugs, medicinal, or biological substances.
- If the same code would describe the causative agent for more than one adverse effect, poisoning, toxic effect, or underdosing, assign the code only once.
- If two or more drugs, medicinal or biological substances are reported, code each individually unless the combination code is listed in the table of drugs and chemicals.
It will take a little bit of adjustment, but all this is pretty mild as coding guideline changes go. I personally feel that it is about time that the adverse effect codes identify the condition. In ICD-9 there was a fine line between poisonings and adverse effect coding. It came down to the fact that poisonings had the 900 poisoning code first and the E code identified how they were poisoned, requiring at least three codes to code it correctly versus the possibility of only two codes for adverse effects. Now the coding will look more alike. Regarding specificity, I think ICD-10 is more appropriate, and I am looking forward to the changes.