The ICD uses a common system to report and track illnesses and medical conditions, which allows providers and researchers to compare and share data. This standardization ensures uniformity in medical research and documentation between different nations and healthcare systems. The ICD provides an accurate and thorough classification of illnesses, medical conditions, and their subgroups. This aids in the detection, diagnosis, and treatment of a wide range of conditions.

The ICD is revised regularly due to advancements in medical knowledge. ICD-11, which was approved by the WHO in 2019 and is meant to replace ICD-10, is the most recent version as of 2024.

The ICD is divided into major sections called “chapters” and minor sections called “blocks”. Under the chapters and blocks, conditions are classified with a code that starts with letters, followed by a combination of numbers and letters which more specifically classify the condition. For example, the 11th chapter of ICD-11 is “Diseases of the Circulatory System”. Under that is a block entitled “Hypertensive diseases”. Under this block exists the code BA00, which includes all types of essential hypertension (high blood pressure that cannot be attributed to another cause). The more specific code BA00.0 indicates high systolic and diastolic blood pressure that are not attributable to other causes, which is a specific type of essential hypertension.

Modifications of the ICD are used for specific applications. The ICD-10-PCS is used to code for inpatient procedures that are done at a hospital in the United States. “PCS” stands for “procedural coding system”. The ICD-10-CM (“CM” stands for “clinical modification”) is used for coding in a wider range of healthcare settings in the United States for billing and reimbursement as well as for research purposes.

More information about the ICD can be found here.