ICD stands for “International Statistical Classification of Diseases and Related Health Problems.” It is one of several standard classification systems used around the world throughout the healthcare system and by government agencies and researchers to track and report diseases, disorders, injuries, and other health conditions. The ICD coding system is maintained by the World Health Organization (WHO). It has gone through 11 revisions over that time. The latest revision, ICD-11 was launched in 2022 although around 150 countries current still use the prior version, ICD-10, and full migration to ICD-11 is expected to take many years to fully implement.
Within the US, a specific version of ICD-10, called ICD-10-CM (ICD revision 10, Clinical Modification), is used and this is managed by the US Centers for Disease Control and Prevention (CDC).
It is estimated that of the around 7000 known rare diseases, only about 500 are currently listed in the ICD system. The lack of an appropriate disease-specific code can create difficulties in accessing insurance and reimbursement for affected individuals and their families. Lack of a specific code also hampers research into these conditions. For example, it has been difficult to estimate the incidence and prevalence of PHTS because of its varied presentations and because some features also commonly occur in the general population.
On the first of October 2022 a unique code for PHTS (Q85.81) was incorporated into ICD-10-CM for use in the medical records of individuals in the US with a PHTS diagnosis. This followed a formal application to the CDC made by PTEN Research Foundation in partnership with Prof. Charis Eng and David Flannery M.D., from Cleveland Clinic Genomic Medicine Institute, and Prof. Marc Tischkowitz, from the Department of Medical Genetics at Cambridge University.
In parallel the same group also applied to the WHO for a revision to the coding for PHTS to ensure it was both scientifically meaningful and comparable to the approach taken by the CDC and later in 2022 the team were informed the request had been successful.
In ICD-11, PHTS has been allocated to stem code LD2D.Y which is shared with several other conditions. However, in addition to this stem code, PHTS has been allocated a unique ‘Uniform Resource Identifier’ (URI) which will enable the identification of individuals with PHTS from electronic health records. The approach taken by the WHO for PHTS is consistent with other rare diseases.