What are ICD-10 Codes?
What are ICD-10 codes? ICD-10 is the tenth edition of the International Classification of Diseases, which is a medical coding system chiefly designed by the World Health Organization (WHO).  ICD-10 codes allow medical billers and coders to classify medical conditions into categories of related diseases under which more specific medical conditions are detailed, which in turn relates those specific conditions to broader morbidities. ICD-10 Codes are then used by medical professionals to code and bill for their services.

The United States’ version of ICD-10 codes was created by the NCHS (National Center for Health Statistics) and The CMS (Centers for Medicare & Medicaid Services) and it is comprised of two medical code sets—ICD-10-CM and ICD-10-PCS.

ICD-10-CM is the broader classification and is used for medical claim reporting in all healthcare settings. It is a standardized and highly evolved classification system of diagnostic coding that denote specific diseases and medical conditions, health problems, abnormal findings, injuries, external causes of injuries and diseases, and a patient’s social and environmental surroundings and circumstances.

In order for a payer to send reimbursement to a medical provider for services they’ve rendered to a patient, they need to receive billing that uses the correct ICD-10-CM codes.  While CPT® codes depict the services provided to the patient, ICD-10-CM codes detail the patient’s diagnoses that justify the services rendered as medical necessities that can be reimbursed.

ICD-10-CM & ICD-10-PCS – What Are The Differences?
Both the ICD-10-CM and ICD-10-PCS coding systems went into effect for medical claims reporting on Oct.1, 2015. But the two code sets differ vastly. The main differences are as follows:

  • ICD-10-CM – This is the diagnosis code set that is used for all healthcare settings
  • ICD-10-PCS – This is the procedural code set that is used exclusively in hospital inpatient settings

The terms ICD-10-CM and ICD-10 are used interchangeably in the United States. This highlights the distinction between CM and PCS since ICD-10-CM is universal across healthcare settings and is used by every medical coder as the only means of reporting diagnoses.

By contrast, the PCS code set is one of two procedural coding systems, however, unlike CPT®, ICD-10-PCS is used strictly in hospital inpatient healthcare settings.

ICD-10 Is A Major Upgrade Over ICD-9 Coding
The reason that ICD-10 codes are superior to the old ICD-9 codes is due to their greater granularity. There are over 70,000 ICD-10 codes currently as opposed to only 13,000 diagnostic codes under the old ICD-9-CM system. The more detailed coding scheme allows for much more specificity in classifying of patients’ diseases, conditions and injuries. This is turn lets medical coders to better document and classify etiologies, anatomic sites, complications, comorbidities and the severity of illnesses.

Providers and payers can use the detail that ICD-10 diagnostic codes offer to track information about patient’s conditions and the types and number of treatments patients receive. Furthermore, they can gather and analyze code data to:

  • Evaluate the efficacy and outcome of patient care
  • Determine the health status and risk factors of various patient groups
  • Monitor and improve providers’ performance
  • Capture and assess healthcare costs
  • Investigate and prevent coding and billing abuses

ICD-10 Code Structure
The ICD-10-CM coding structure includes an:

  • Official Index
  • Official Conventions
  • Official Guidelines

These are designed to help medical coders find and assign the correct diagnosis codes for their patient’s conditions.

Instructions and Conventions
The ICD-10 codes set includes:

Section I Conventions
These are general coding guidelines applicable to the overall classification, and chapter-specific guidelines.

Sections II – IV Conventions
These outline the principles and rules guiding the selection of primary diagnoses, reporting on additional diagnoses, and diagnostic coding and reporting of outpatient services.

Also, the Official Guidelines for Coding and Reporting, which is based upon the sequencing instructions in the Tabular List and Alphabetic Index of ICD-10-CM, deliver additional guidance in assigning the correct ICD-10 coding to specific conditions.

The ICD-10 Alphabetic Index
The ICD-10 Alphabetic Index is a 4-part index, which encompasses the following:

  • Index of Diseases and Injury
  • Index of External Causes of Injury
  • Table of Neoplasms
  • Table of Drugs and Chemicals

Each of the above is designed to streamline the process of locating the necessary diagnosis codes and ICD-10 coding instructions.

Index to Diseases & Injuries
The Index to Diseases & Injuries lists diseases, injuries, and diagnostic terms, along with their associated codes (or code categories). Additionally, sub-lists of more detailed or related terms with their corresponding codes appear beneath many of the main terms.

Table of Drugs and Chemicals
The Table of Drugs and Chemicals allows you to locate codes for poisoning or allergic reactions by cross-referencing the substance in question with one of six situations that specify whether the substance-related condition was accidental, intentional self-harm, assault, undetermined, adverse effect, or the result of underdosing.

Index of External Causes of Injury
ICD-10 external cause codes provide details explaining the events surrounding an injury, which are especially useful in collecting statistics for public health policy formation. These ICD-10 codes also play an important role in workers’ compensation claims.

The Index of External Causes of Injury has a very similar arrangement to the Index to Diseases and Injuries and details entries and sub-entries in alphabetical order along with their corresponding codes.

Tabular List
The Tabular List refers to the actual listing of ICD-10 codes and their descriptors. In the Tabular list, coders will also find instructions that can help in the correct application of the codes, as well as lists of additional diagnoses that a code applies to, sequencing rules, or which diagnoses codes are excluded from an ICD-10 code.

The Tabular List is organized into 21 chapters according to body system or condition, with diagnosis codes listed alphanumerically in each chapter.

ICD-10-CM Chapters and Code Ranges

Chapter Code Range Description

  • A00-B99 Certain Infectious and Parasitic Diseases
  • C00-D49 Neoplasms
  • D50-D89 Diseases of the Blood and Blood-Forming Organs and Certain Disorders Involving the Immune Mechanism
  • E00-E89 Endocrine, Nutritional and Metabolic Diseases
  • F01-F99 Mental, Behavioral and Neurodevelopmental Disorders
  • G00-G99 Diseases of the Nervous System
  • H00-H59 Diseases of the Eye and Adnexa
  • H60-H95 Diseases of the Ear and Mastoid Process
  • I00-I99 Diseases of the Circulatory System
  • J00-J99 Diseases of the Respiratory System
  • K00-K95 Diseases of the Digestive System
  • L00-L99 Diseases of the Skin and Subcutaneous Tissue
  • M00-M99 Diseases of the Musculoskeletal System and Connective Tissue
  • N00-N99 Diseases of the Genitourinary System
  • O00-O9A Pregnancy, Childbirth and the Puerperium
  • P00-P96 Certain Conditions Originating in the Perinatal Period
  • Q00-Q99 Congenital Malformations, Deformations, and Chromosomal Abnormalities
  • R00-R99 Symptoms, Signs, and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified
  • S00-T88 Injury, Poisoning, and Certain Other Consequences of External Causes
  • V00-Y99 External Causes of Morbidity
  • Z00-Z99 Factors Influencing Health Status and Contact with Health Services

Using the ICD-10 Tabular List
ICD-10 codes always start with a letter, which is followed by 2 numbers. The first 3 characters refer to the code category and represent a disease or group of related diseases, common traits, and conditions.

Once you find an ICD-10 code in the Alphabetic Index, you’ll need to review the code details and instructions in the Tabular List to confirm that it’s the right diagnosis code and to code it properly.

In the chapters listed above, the code ranges are included in the titles. These sets of alphanumeric characters further define the chapter title by denoting the categories contained within it.

Additionally, the code range within each chapter in the Tabular List is broken down into subchapters called blocks.

Structure of ICD-10 Codes
ICD-10-CM codes consist of three to seven characters. Every code begins with an alpha character, which is indicative of the chapter to which the code is classified. The second and third characters are numbers. The fourth, fifth, sixth, and seventh characters can be numbers or letters.

Here are some examples of ICD-10 codes, their structure, and the conditions they represent.

  • I25 – Chronic ischemic heart disease
  • 1 – Atherosclerotic heart disease of native coronary artery

Additional Related Codes

  • chronic total occlusion of coronary artery (I25.82)
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)
  • Excludes2: non-ischemic myocardial injury (I5A

The ICD-10 code depicts greater diagnostic information through additional characters, which are incorporated using a decimal point following the category and preceding the subcategory. Every character to the right of the decimal point adds specific information about the diagnosis. When coding, it is important to always code diagnoses to the greatest level of specificity available in the ICD-10 code set.

Every ICD-10 code represents a unique diagnosis. That is why it is important to always assign subdivisions until you have coded to the highest level of specificity when submitting codes to payers, billing agencies, claims clearinghouses, and collection agencies.

ICD-10-PCS Overview
The PCS in ICD-10-PCS stands for procedural classification system. ICD-10-PCS is an inpatient medical coding scheme with a structure that follows a logical, consistent process down to each character level in each code.

ICD-10-PCS is completely separate from ICD-10-CM and the design is based on direction from the NCVHS (National Committee on Vital and Health Statistics). ICD-10-PCS is completely separate from ICD-10-CM.

The structure of ICD-10-PCS must be:  

  • Standardized — Each of the seven alphanumeric characters in an ICD-10-PCS code represent the details of a procedure including the body part, medical approach, and any devices. Each ICD-10-PCS code creates its descriptor, and all descriptors are uniform, covering the same type and level of specificity.
  • Unique — A unique PCS code is available for each significantly different procedure, and each code retains its own unique definition. Codes are not reused or modified. For instance, the same procedure performed on a different body part has its own code and every procedure that uses a different approach has its own unique code.
  • Expandable — The structure of PCS is expandable and is designed to accommodate emerging procedures and technologies that will allow for the creation of new codes without disrupting the system. This is accomplished through adding alpha-numeric characters.
  • Standardized Terminology — The terminology used in ICD-10-PCS is standardized to provide precise and stable definitions of all procedures.

ICD-10-PCS System Organization
ICD-10-PCS is composed of 17 sections, represented by the numbers 0–9 and the letters B–D, F–H and X. The broad procedure categories contained in these sections range from surgical procedures to substance abuse treatment and new technology.

The 17 ICD-10-PCS Sections

Code   Section Description
0 – Central Nervous System and Cranial Nerves, Medical and Surgical
1 – Pregnancy, Obstetrics
2 – Anatomical Regions, Placement
3 – Circulatory, Administration
4 – Physiological Systems, Measurement and Monitoring
5 – Physiological Systems, Extracorporeal or Systemic Assistance and Performance
6 – Physiological Systems, Extracorporeal or Systemic Therapies
7 – Anatomical Regions, Osteopathic
8 – Indwelling Device, Other Procedures
9 – Anatomical Regions, Chiropractic
B – Central Nervous System, Imaging
C – Central Nervous System, Nuclear Medicine
D – Central and Peripheral Nervous System, Radiation Therapy
F – Rehabilitation, Physical Rehabilitation and Diagnostic Audiology
G – None, Mental Health
H – None, Substance Abuse Treatment
X – Cardiovascular System, New Technology

Medical & Surgical Section
All of the codes in the Medical and Surgical section begin with the section value 0. The 67,655 codes in the Medical and Surgical section represent the majority of the 78,103 PCS codes. All of these PCS codes are used solely in inpatient and hospital settings in the U.S.

Medical & Surgical Related Sections
Sections 1–9 of ICD-10-PCS are the Medical and Surgical Related sections. These sections include obstetrical procedures, administration of substances, measurement and monitoring of body functions, and extracorporeal therapies.

Ancillary Sections
Sections B–D and F–H are the ancillary sections of ICD-10-PCS. These six sections include imaging procedures, nuclear medicine, and substance abuse treatment.

Structure of PCS Codes
All ICD-10-PCS codes consist of seven characters. Each character can be one of 34 values which are the numbers 0 through 9 and the letters of the alphabet, minus O and I (to avoid confusion with numbers zero and one). The 34 possible character values give ICD-10-PCS a range of meaning for detailed coding.

To learn more about ICD-10 codes and coding, contact the experts at Coding & Billing Solutions today!