The ICD-9 code sets used to report medical diagnoses and inpatient procedures will be replaced by ICD-10 code sets on October 1, 2015. ICD-10 consists of two parts:

  • ICD-10-CM diagnosis coding which is for use in all U.S. health care settings.
  • ICD-10-PCS inpatient procedure coding which is for use in U.S. hospital settings.

ICD-10 will affect diagnosis and inpatient procedure coding for everyone covered by the Health Insurance Portability Accountability Act (HIPAA), not just those who submit Medicare or Medicaid claims:

  • Claims for services provided on or after the compliance date should be submitted with ICD-10 diagnosis codes.
  • Claims for services provided prior to the compliance date should be submitted with ICD-9 diagnosis codes.

The change to ICD-10 does not affect CPT coding for outpatient procedures.

ICD-10 allows us to speak the same language as the people that are going to be telling our story – for outcomes, for data assessment, and for billing. It’s incredibly important to have the severity of disease we are managing accurately portrayed.

Mark Bieniarz, M.D.
Cardiologist

ICD-10-CM Code Structure

ICD-10 diagnosis codes have between 3 and 7 characters:
ICD-10-CM Code Structure

  • Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by the use of any or all of the 4th, 5th, and 6th characters. Digits 4-6 provide greater detail of etiology, anatomical site, and severity. A code using only the first three digits is to be used only if it is not further subdivided.
  • A code is invalid if it has not been coded to the full number of characters required. This does not mean that all ICD-10 codes must have 7 characters. The 7th character is only used in certain chapters to provide data about the characteristic of the encounter. Examples of where the 7th character can be used include injuries and fractures, as illustrated in the following tables:
    Injuries and External Causes Fractures
    Value Description Value Description
    A Initial encounter A Initial encounter for closed fracture
    D Subsequent encounter B Initial encounter for open fracture
    S Sequela D Subsequent encounter for fracture with routine healing
    G Subsequent encounter for fracture with delayed healing
    K Subsequent encounter for fracture with nonunion
    P Subsequent encounter for fracture with malunion
    S Sequela
  • A dummy placeholder of “X” is used with certain codes to allow for future expansion and/or to fill out empty characters when a code contains fewer than 6 characters and a 7th character applies. When a placeholder character applies, it must be used in order for the code to be considered valid.
  • Below are specific examples of ICD-10 diagnosis codes. The use of combination codes, increased specificity, and the “X” placeholder is illustrated:
    Code Description
    Combination Codes
    I25.110 Atherosclerotic heart disease of native coronary artery with unstable angina pectoris
    Increased Specificity
    S72.044G Non-displaced fracture of base of neck of right femur, subsequent encounter for closed fracture with delayed healing
    Laterality
    C50.511 Malignant neoplasm of lower-outer quadrant of right female breast
    C50.512 Malignant neoplasm of lower-outer quadrant of left female breast
    “X” Placeholder
    H40.11X2 Primary open-angle glaucoma, moderate stage

ICD-10-CM Indexes

A comprehensive listing of 2015 diagnosis codes can be found in the ICD-10-CM Index to Diseases and Injuries (alphabetical) and ICD-10-CM Tabular List of Diseases and Injuries which can be accessed from the following links:

A summary of the chapters found in the Tabular List has been provided below:

Chapter Code Range Estimated # of Codes Description
1 A00-B99 1,056 Certain infectious and parasitic diseases
2 C00-D49 1,620 Neoplasms
3 D50-D89 238 Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
4 E00-E89 675 Endocrine, nutritional and metabolic diseases
5 F01-F99 724 Mental, Behavioral and Neurodevelopmental disorders
6 G00-G99 591 Diseases of the nervous system
7 H00-H59 2,452 Diseases of the eye and adnexa
8 H60-H95 642 Diseases of the ear and mastoid process
9 I00-I99 1,254 Diseases of the circulatory system
10 J00-J99 336 Diseases of the respiratory system
11 K00-K95 706 Diseases of the digestive system
12 L00-L99 769 Diseases of the skin and subcutaneous tissue
13 M00-M99 6,339 Diseases of the musculoskeletal system and connective tissue
14 N00-N99 591 Diseases of the genitourinary system
15 O00-O9A 2,155 Pregnancy, childbirth and the puerperium
16 P00-P96 417 Certain conditions originating in the perinatal period
17 Q00-Q99 790 Congenital malformations, deformations and chromosomal abnormalities
18 R00-R99 639 Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
19 S00-T88 39,869 Injury, poisoning and certain other consequences of external causes
20 V00-Y99 6,812 External causes of morbidity
21 Z00-Z99 1,178 Factors influencing health status and contact with health services

External Cause Code Reporting

If you have not been reporting ICD-9-CM external cause codes, you will not be required to report ICD-10-CM codes found in Chapter 20 unless a new State or payer-based requirement about the reporting of these codes is instituted. If such a requirement is instituted, it would be independent of ICD-10-CM implementation.

In the absence of a mandatory reporting requirement, you are encouraged to voluntarily report external cause codes, as they provide valuable data for injury research and evaluation of injury prevention strategies.

Native Coding and Unspecified Codes

Native coding means to assign an ICD-10 diagnosis code directly based on clinical documentation. Practices are encouraged to natively code using ICD-10 code reference sources instead of using crosswalks, which should be used for general knowledge. Specific codes reflecting the most appropriate level of certainty known for an encounter should be evaluated first:

  • Specific diagnosis codes should be reported when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition.
  • If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and/or symptom(s) in lieu of a definitive diagnosis.
  • When sufficient clinical information is not known or available about a particular health condition to assign a more specific code, coding should comply with the payer guidelines for the use of unspecified codes.



As with major changes in any industry, the transition to ICD-10 will require focused effort and attention. Use of this portal can help you overcome these challenges. Get started today!
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