ICD-10-CM Enhancements: A Look at the Features That Will Improve Coding Accuracy

by Ann Zeisset , RHIT, CCS, CCS-P

Although the ICD-10-CM/PCS final rule sets an implementation deadline of October 2013, facilities should start preparing now for the new code set. All facilities reporting ICD-9-CM codes for diagnoses must transition to ICD-10-CM for diagnosis reporting.

ICD-10-CM implementation will have a larger impact than ICD-10-PCS, since PCS is used only in the hospital inpatient setting by those reporting ICD-9-CM procedure codes. All other entities report CPT and HCPCS codes.

Although many coding professionals need ICD-10-CM training, the ICD-10-CM and ICD-9-CM classification systems are similar. The ICD-10-CM system builds on concepts that coding professionals already recognize. It also includes major enhancements to the system. This article discusses some of the major enhancements ICD-10-CM provides.

Similarities in Structure and Terms

ICD-10-CM has the same type of hierarchy in its structure as ICD-9-CM. All codes have the same first three digits describing common traits, with each character beyond the first three providing more specificity.

ICD-10-CM also has the same organization and use of notes and instructions. When a note appears under a three-character code, it applies to all codes within that category, and notes under a specific code apply to the single code.

Even though ICD-10-CM has more characters (up to seven) and uses alpha characters, each code must be at least three characters, with a decimal point used after the third character. The additional characters following the decimal point describe the etiology, anatomic site, or severity.

ICD-10-CM consists of an alphabetic index formatted by main terms listed in alphabetic order with indentations for any applicable qualifiers or descriptors. Familiar punctuation such as brackets, parentheses, colons, and commas are used in ICD-10-CM, as are terms such as Not Elsewhere Classified (NEC), Not Otherwise Specified (NOS), “code first,” “Use additional code,” and “code also” notes familiar to coding professionals.

Cross references are included to provide instructions to reference other or additional terms. The tabular list is presented in code number order and used like ICD-9-CM.

Combination Codes Solve Sequencing Dilemmas

ICD-10-CM includes combination codes for conditions and common symptoms or manifestations. A single code may be used to classify two diagnoses, a diagnosis with an associated sign or symptom, or a diagnosis with an associated complication. This allows one code to be assigned, resulting in fewer cases requiring more than one code and reducing sequencing problems.

Coding professionals have encountered sequencing dilemmas when coding conditions such as unstable angina with arteriosclerotic heart disease or diabetes mellitus with a complication/manifestation such as diabetic nephropathy. Manifestation/etiology conditions require two codes with sequencing mandated by ICD-9-CM. Brackets in the index identified that the etiology (diabetes mellitus) code was sequenced before the manifestation (diabetic nephropathy).

In cases when ICD-9-CM did not indicate correct sequencing, coding was not clear-cut, and Coding Clinic advice was needed to sequence conditions appropriately. The ICD-10-CM use of combination codes has greatly simplified this process.

Combination codes are also available for external causes and poisonings, with information combined into one code (including the drug involved) making those difficult sequencing rules obsolete.

Examples of these combination codes include:

  • I25.110, Atherosclerotic heart disease of native coronary artery with unstable angina pectoris
  • E10.21, Type 1 diabetes mellitus with diabetic nephropathy
  • N30.01, Acute cystitis with hematuria
  • T39.011A, Poisoning by aspirin, accidental (unintentional), initial encounter

Full Descriptions Reduce Cross-Referencing

To assign fourth or fifth digits in ICD-9-CM, the coding professional is referred back to a previous page, section, or even chapter to identify the digit. This often results in coding errors. ICD-10-CM has made every attempt to write out the full code title for all codes, decreasing cross-references. This change provides greater comprehension of the meaning of the code, as well as facilitates computer applications.

Take for example the ICD-9-CM code 147.0, Superior wall. It is necessary to know the category of this code (147, Malignant neoplasm of nasopharynx) to identify the site correctly.

The code description for ICD-10-CM code C11.0, Malignant neoplasm of nasopharynx, stands on its own without knowing the category (C11, Malignant neoplasm of nasopharynx).

Choosing Sides with Laterality

ICD-10-CM includes codes for laterality (unclassified in ICD-9-CM). Codes for left side, right side, and in some cases bilateral are available in appropriate chapters. If the side is not documented in the medical record, an unspecified side code is available. The majority of the affected codes are in the neoplasm and injury chapters. The classification of this information can be very beneficial in reporting claims for payment, and documentation of this information is usually readily available in the health record.

Examples of these types of codes include:

  • C50.511, Malignant neoplasm of lower-outer quadrant of right female breast
  • M21.722, Unequal limb length (acquired), left humerus
  • S72.344A, Nondisplaced spiral fracture of shaft of right femur, initial encounter for closed fracture

Expanded Codes Capture More Detail

Expanded codes are available in many sections of ICD-10-CM, particularly in the injury, diabetes, alcohol and substance abuse, and postoperative complication sections. There are five categories for diabetes in ICD-10-CM: E08, Diabetes due to underlying condition; E09, Drug or chemical induced diabetes; E10, Type 1 diabetes; E11, Type 2 diabetes; and E13, Other specified diabetes mellitus. Controlled or uncontrolled is not a classification in ICD-10-CM.

The codes for postoperative complications include a distinction between intraoperative complications and postprocedural disorders. Newly recognized conditions and conditions not uniquely identified in ICD-9-CM have been given codes, such as subsequent myocardial infarction, mesothelioma, and secondary diabetes.

Injuries are grouped by body part rather than by categories of injury, so that all injuries of the specific site (such as head and neck) are grouped together rather than groupings of all fractures or all open wounds.

For example, categories in ICD-9-CM grouped by injury such as fractures (800–829), dislocations (830–839), and sprains and strains (840–848) now would be grouped in ICD-10-CM by site, such as injuries to the head (S00–S09), injuries to the neck (S10–S19), and injuries to the thorax (S20–S29).

Extensions Specify Encounter

ICD-9-CM limitations have created challenges in assigning codes for specific aftercare encounters in the outpatient and postacute care settings. ICD-9-CM has added codes for this purpose in the last several years, but codes are still limited. ICD-10-CM has added code alpha character extensions (seventh character) in appropriate sections to provide specific information about the characteristics of the encounter.

In the injury and external cause sections, the extension classifies an initial encounter, subsequent encounter, or sequelae of an encounter. Extensions have different meanings depending on the section, but common extensions are:

  • A, Initial encounter
  • D, Subsequent encounter
  • S, Sequelae

In code S81.012, Laceration without foreign body, left knee, the seventh character would be A for an initial encounter, D for subsequent encounter, or S for sequelae.

Certain codes, such as fractures have more specificity provided by the extension, identifying such conditions as closed fractures, open fractures (with type), routine healing, delayed healing, and nonunions. In code S49.011, Salter-Harris Type I physeal fracture of upper end of humerus, right arm, a D extension would indicate a subsequent encounter (aftercare) for fracture with routine healing.

Extensions in the obstetrics section provide information about the fetus (either single or the identification of the fetus if multiple). Trimesters are identified in ICD-10-CM, not the episode of care.

Flexibility Allows Specificity

Because of the flexibility and expandability of the ICD-10-CM coding system, it is possible to provide more specificity in the coding of many conditions. This results in major improvements in the quality and usefulness of the data for all current uses of the coding system. When developing the clinical modification to ICD-10, the National Center for Health Statistics consulted with various physician groups to determine where the greater detail would be advantageous.

Examples of more specific codes include:

  • S72.324A, Nondisplaced transverse fracture of shaft of right femur, initial encounter for closed fracture
  • S45.311S, Laceration of superficial vein at shoulder and upper arm level, right side, sequela
  • M08.251, Juvenile rheumatoid arthritis with systemic onset, right hip
  • T81.535D, Perforation due to foreign body accidentally left in body following heart catheterization, subsequent encounter

Further, standard definitions have been added to facilitate the coding process. An example is the definition for two types of Excludes notes. Excludes1 is a pure excludes note. It means “do not code here.” This note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. This note is used when two conditions cannot occur together, such as a congenital condition versus an acquired condition.

Excludes2 notes represent “Not included here.” This note indicates that the condition excluded is not part of the condition represented by the code, but that a patient may actually have both conditions at the same time. When this is the case, it is acceptable to use both codes together.

The increased data specificity and clinical detail provided by this new classification system will allow the United States to better measure quality, safety and efficacy of care; design payment systems and process claims for reimbursement; conduct research, epidemiological studies, and clinical trials; set health policy; strategically plan and design healthcare delivery systems; monitor resource utilization; prevent and detect healthcare fraud and abuse; and track public health risks.


National Center for Health Statistics. “ICD-10-CM Index and Tabular.” 2007. Available online at www.cdc.gov/nchs/about/otheract/icd9/icd10cm.htm.

For more ICD-10 resources-and for the latest ICD-10 news-visit www.ahima.org/icd10.

Ann Zeisset (ann.zeisset@ahima.org) is manager of professional practice resources at AHIMA.

Article citation:
Zeisset, Ann M.. "ICD-10-CM Enhancements: A Look at the Features That Will Improve Coding Accuracy" Journal of AHIMA 80, no.2 (February 2009): 55-58.