Preparing for ICD-11 in the US Healthcare System

Introduction

International Classification of Diseases 11^th Revision (ICD-11) became available for use globally as of January 1, 2022.¹ The ICD system was originally designed to enable disease-specific epidemiological tracking of morbidity and mortality. Over time, the ICD system has been leveraged for a variety of additional uses, most notably to support billing and reimbursement, healthcare quality and safety, and health services research (Figure 1). Because of the many downstream dependencies, upgrading to the new and powerful ICD-11 system will require a minimum of 4–5 years of time, effort, and resources.² In preparation, the World Health Organization (WHO) has published reference and implementation guides and there are extensive efforts to test ICD-11 prior to full scale deployment.^1–3 Nevertheless, successful rollout of ICD-11 across the United States (US) healthcare system will require ongoing and expanded efforts to ensure that ICD-11 meets the diverse real-world needs of its end users. We highlight the major changes in the ICD-11 system, several associated downstream challenges, and key strategies necessary to prepare for full implementation of ICD-11.

Figure 1. The Many Uses of the ICD System in the United States.

This figure summarizes the major aspects of the US healthcare system that are currently dependent on the ICD system.

The Evolution of the ICD System

Created in the 1800s, the ICD system was initially used to classify causes of death. By 1948, the WHO adopted ICD-6, which formed the basis for the current-day ICD system.⁴ In 1962, the US Public Health Service began developing customized US-specific versions to increase the utility of the system for classifying hospitalizations and procedures.⁴ In 1977, the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics again adapted ICD-9 through a set of custom “clinical modifications” (CMs) to enhance diagnostic coding in the US. By 1983, the resulting ICD-9-CM system became integral for the calculation of Medicare payments using Diagnosis-Related Groups. In 2009, the US mandated that CMS adopt ICD-10-CM by 2015, which solidified our commitment to utilizing ICD across many healthcare domains (Figure 1).

Benefits of the New ICD-11 System

Like the US, many other countries have made customized modifications to the ICD system, leading to inconsistent worldwide implementation.⁵ Consequently, the WHO redesigned ICD-11 as a more comprehensive, fully digital system that, theoretically, could be used “off-the-shelf” without the need for additional modifications, and that would be continually updated and harmonized with other medical information terminologies.¹ Three major benefits are worth mentioning. First, ICD-11 introduces many specific diagnoses that were previously left out, enabling more precise and detailed data collection. New classes of codes (e.g., “Diseases of the Immune System”) and more than 5,500 rare diseases are now represented.¹ Second, ICD-11 introduces a novel “clustered” code structure comprised of a “stem” code joined to optional “post-coordination” codes.¹ Multiple post-coordination codes can be combined to convey various clinical details, for example, laterality or severity. This makes the system flexible and clinically useful without the need for local customizations that are time-consuming, costly, and interfere with international comparisons. Third, given its semantic linkage to Systemized Nomenclature of Medicine Clinical Terms (SNOMED-CT, the international standard for exchange of electronic clinical health information), ICD-11 has the potential to support automated or artificial-intelligence-assisted coding.²

Challenges Associated with ICD-11 Implementation

Nothing comes without a price. First, the new ICD-11 code format requires sophisticated crosswalk mapping of more than 70,000 existing ICD-10-CM codes to their corresponding new ICD-11 codes. This is not a simple or straightforward one-to-one process. In a 2021 study, only 23.5% of ICD-10-CM codes could be fully represented by a single ICD-11 stem code, meaning that clinicians and coders will have to assign multiple post-coordination codes to capture the same level of information contained within single ICD-10-CM codes.⁶ Second, every ICD-dependent process will be affected. All billing and quality measures will require redesign. Data processing algorithms, statistical programs, and classification software that handle ICD codes will need to be updated. For example, the Healthcare Cost and Utilization Project maintains ICD-based analytical tools used to inform national healthcare decisions that have only recently finished being updated to ICD-10-CM; similar lags in translation to ICD-11 will have real-world consequences. Finally, the new “clustered” code structure has major ramifications. Data standards for electronic health record systems and databases will need to be modified to accommodate the longer character lengths necessary to store ICD-11 codes utilizing the “clustered” code structure. Even with the correct technology, whether healthcare systems and bedside clinicians fully utilize clustered codes will depend on contextual reporting requirements, proper education, and the necessary information technology and workforce to implement ICD-11. Differences in implementation strategies between institutions could result in differential data quality and impact revenue, further exacerbating inequities across the healthcare system.

Ensuring Preparedness for ICD-11

More than 60 countries have already adopted ICD-11 and evaluated its performance across different scenarios, ranging from case-mix adjustment to adverse event reporting.³ As the US similarly implements ICD-11, several key strategies can promote success. First, as recommended by the Department of Health and Human Services, active exploration of ICD-11 must continue broadly throughout the US healthcare system and should engage all potential end users.⁷ Although US governmental agencies have begun evaluations of major ICD-dependent processes, there are numerous other inconspicuous but important use cases; end users are best positioned to identify these for further attention.^8–10 Second, many of the implementation endeavors rely on the availability of transition tools, like crosswalk mapping files, translation software, and dual-coded datasets (including both ICD-10-CM and ICD-11 codes). These should be created and made publicly available well before the anticipated transition date. Finally, all of these efforts will require federal-state-industry partnerships, including substantial grant funding and project resources, to support the training, implementation, and evaluation of the transition to ICD-11 across all aspects of healthcare.⁸

Conclusion

Because the ICD system provides the disease classification infrastructure for the US healthcare system, we must continue to invest in and prepare for ICD-11. End users should consider how ICD-11 will impact existing ICD-dependent processes within their fields and share this knowledge upward within healthcare systems. Solutions can then be tested and implemented to standardize and minimize the required transition work. This will ensure that ICD-11 meets the many needs of its end users.

Abbreviations:

CM

Clinical Modification

CMS

Centers for Medicare and Medicaid Services

ICD

International Classification of Diseases

SNOMED-CT

Systemized Nomenclature of Medicine Clinical Terms

WHO

World Health Organization