Under the current system, chronic pain conditions are poorly categorized under the code ICD-10, which makes it difficult for complex conditions such as fibromyalgia and Complex Regional Pain Syndrome (CRPS) to be classified. That led some physicians to diagnose patients with unexplained pain as having a somatic symptom disorder.

“A diagnosis of somatic symptom disorder implies that the pain is caused by a behavioral, that is, mental condition. However, it is not appropriate to diagnose individuals with a mental disorder solely because an alternative medical cause cannot be established,” Jaochim Scholtz, MD, an IASP task force member, explained in Practical Pain Management.

Under the new coding system, patients with fibromyalgia or CRPS could be classified as having a “primary pain” disorder, one of seven new sub-codes for chronic pain conditions:

Chronic primary pain Chronic cancer-related pain Chronic post-surgical or post-traumatic pain Chronic neuropathic pain Chronic secondary headache or orofacial pain Chronic secondary visceral pain Chronic secondary musculoskeletal pain.

There is some overlap between the different diagnostic codes. For example, neuropathic pain can be a symptom of cancer or chemotherapy, while trigeminal neuralgia could fall under neuropathic or orofacial pain. The idea is to give physicians a range of codes to choose from instead of the limited choices they have today.

“The integration of chronic pain in ICD-11 sends a strong signal that pain will achieve appropriate representation in this international standard for reporting diseases and health conditions,” said Scholtz. “The coding system also provides fundamental information for the identification of health trends and healthcare planning. It is widely hoped that the new systematic classification of chronic pain in the ICD-11 will support epidemiological, and other research that is essential for the development of future health policies.”

The classification system was outlined in a free online article published in the January 2019 issue of PAIN.﻿