Oakland – A new California Workers’ Compensation Institute (CWCI) report on the use of ICD-10 codes in California workers’ comp during the transition from the ICD-9 system finds that 99% of submitted medical bills used ICD-10 codes and, as expected, a wider range of codes were provided than in the past, but many lacked the additional characters that better define the injury, identify the type of encounter and improve communication.

On October 1, 2015, the 10^th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) became the standard classification system for all healthcare delivery systems in the U.S., including workers’ comp. The adoption of the new system was the first time in 21 years that the codes used by medical providers to describe a patient’s clinical status had been updated. The transition from the outdated ICD-9 coding system was primarily intended to allow more accurate and precise descriptions of a patient’s clinical status in order to facilitate communication between medical providers, providers and payers, and government agencies, though the new code sets also enable statistically relevant groupings, which will improve the data used to track public health conditions, conduct epidemiological research on illnesses and co-morbidities, and assess the types and outcomes of care provided to patients (including the use and effects of new medical technology). Following Medicare’s lead, the California Division of Workers’ Compensation allowed medical providers a one-year transition period during which they could use ICD-10 codes that did not strictly meet the level of coding specificity called for by the new classification format and structure, but as of October 1, 2016, workers’ comp medical services that are not coded at the required specificity level are out of compliance.

The CWCI report, the first in a two-part series, examines the components of injury classification and compares ICD-9 diagnostic codes submitted by California workers’ comp medical providers in the final nine months under the old coding system to the ICD-10 codes submitted in the first nine months of the transition period. Key findings from the analysis:

• The top 10 ICD-10 diagnoses accounted for 20.4% of the primary diagnoses submitted in the first nine months of the transition.
• Diagnosis codes related to lumbar spine injuries accounted for 6 of the top 10 ICD-10 codes for services rendered in the first nine months of the transition. Despite high levels of specificity allowed by the ICD-10s, lumbar spine codes ranged from very low specificity (i.e., “low back pain” was the number one code submitted) to more specific diagnoses such as radiculopathy, disc displacement and disc degeneration.
• More than 1 in 5 ICD-10 codes submitted for shoulder pain diagnoses failed to include a sixth character to identify which shoulder was injured.
• A diagnosis of “injury, unspecified” continued to account for 1.6 percent of primary diagnosis codes under ICD-10, as was the case under ICD-9 submissions.

CWCI has published its analysis as a Research Update report, Injury Classification in California Workers’ Comp, Part 1: Medical Coding During the ICD-10 Transition, which is available from the CWCI store at www.cwci.org, or CWCI members and subscribers may log in to download a copy from the Research section of the website. Part 2 of the series will compare the two diagnosis and injury classification systems now used in California workers’ compensation: the ICD-10 codes submitted by medical providers and the body part, nature of injury, and cause of injury data noted by claims administrators.