Chapter 7
ICD-10-CM Diagnosis Coding
1. Define terms, phrases, abbreviations, and acronyms.
2. Provide a brief overview of the evolution of diagnosis coding to ICD-10-CM.
3. Discuss the impact ICD-10 on documentation, coding, medical necessity, claim forms, and reimbursement.
4. Identify three key areas of ICD-10-CM data usage and discuss organizations that use ICD-10-CM data.
5. Demonstrate an understanding of various aspects of the ICD-10-CM transition, including certification, mapping and crosswalks, and the ICD-10-CM Coordination and Maintenance Committee.
6. State key differences between ICD-10-CM and ICD-9-CM.
7. Provide an outline of ICD-10-CM manual content and explain the use of each section.
8. Identify coding conventions and apply coding principals related to conventions and coding.
9. Demonstrate an understanding of the steps to coding using the ICD-10-CM diagnosis coding system.
Adverse reaction (adverse effect)
International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM)
International Classification of Diseases, 10th Revision (ICD-10)
International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM)
International Classification of Diseases, 10th Revision, Procedure Coding System (ICD-10-PCS)
International List of Causes of Death
American Academy of Professional Coders
American Health Information Management Association
Acquired immune deficiency syndrome
American National Standards Institute
Centers for Disease Control and Prevention
Clinical documentation improvement
Centers for Medicare and Medicaid Services
Department of Health and Human Services
Health Insurance Portability and Accountability Act
International Classification of Diseases
International Classification of Diseases, 9th Revision, Clinical Modification
International Classification of Diseases, 10th Revision
International Classification of Diseases, 10th Revision, Clinical Modification
International Classification of Diseases, 10th Revision, Procedure Coding System
Inpatient Prospective Payment System
Medicare Severity-Diagnosis Related Groups
National Center for Health Statistics
Severe acute respiratory syndrome
Hospital coding and billing professionals will be required to have an understanding of the ICD-9-CM coding system and will need to transition to ICD-10. In an effort to provide current and future knowledge required for hospital professionals, this text presents concepts on coding using ICD-9-CM and ICD-10. The previous chapter presented concepts on coding medical conditions and significant procedures using ICD-9-CM. This chapter will focus on coding medical conditions using the ICD-10-CM coding system.
Evolution of Diagnosis Coding
As discussed in the prior chapter, the evolution of classification systems for coding medical conditions dates back to the 17th century, when systems were originally developed to track the number of deaths in children. Coding of medical conditions (diseases) began in England in the 17th century with the work of John Graunt. John Graunt developed the London Bills of Mortality in an attempt to estimate the proportion of live-born children who died before reaching the age of 6 years. As centuries passed, the attempts to classify causes of death and diseases continued. The International List of the Causes of Death was developed based on the London Bills of Mortality. I was presented at the International Statistical Institute and was adopted in 1893. Several countries adopted the International List of the Causes of Death during the 19th century. Six revisions were made to the International List of the Causes of Death through 1948, and the sixth revision included a name change to the International Classification of Diseases (ICD). The Interim Commission of the World Health Organization (WHO) was given the responsibility for the sixth revision and also for the establishment of a list of causes of morbidity for international use. Information about the World Health Organization (WHO) can be viewed on its Web site at www.who.int/en/.
Impact of ICD-10
Documentation
• Ambulatory and managed care encounter information such as the designation of encounters for fracture care as initial, subsequent, or sequela. Fracture care also requires information regarding healing of the fracture, including delayed, failure to heal, malunion, or non-union.
• Expanded injury codes including designations for encounters.
• Combination codes that describe the diagnosis and symptom or manifestation such as heart disease with angina or diabetes with retinopathy. Poisoning and adverse effect codes include the external cause of injury.
• Left and right designations are included within the codes ranges; right side is “1,” left side is “2,” and bilateral is “3.”
• Higher level of detail to explain the condition and the severity, such as heart failure codes that require documentation of the type of failure: systolic, diastolic, acute, and/or chronic or ulcer codes that require indication of staging. Fracture coding requires documentation of the type of fracture such as greenstick or spiral; open or closed; displaced or non-displaced; right or left; and the episode of care. In addition, fracture coding requires specification of the exact bone and the exact location within the bone.
Claim Forms

Reporting Diagnoses – CMS-1450 (UB-04)
It is important for coders to understand what diagnosis is required for the claim form, where the diagnosis code is recorded, and what coding guidelines apply to the patient case, as illustrated in Table 7-1. ICD-10-CM implementation has not changed the reporting requirements for diagnoses on the CMS-1450 (UB-04). The form is used to submit facility charges for outpatient, non-patient, and inpatient services provided by a hospital or other facility. The CMS-1450 (UB-04) contains 81 fields referred to as form locators (FL). The CMS-1450 (UB-04) claim form completion requirements include the reporting of all patient diagnoses to explain the medical reason for the admission and services provided. Figure 7-9 illustrates how ICD-10-CM diagnosis code(s) are recorded on the CMS-1450 (UB-04).
TABLE 7-1
Claim Variations for ICD-10-CM Diagnosis Codes
ICD-10-CM diagnosis codes will be used to report patient conditions or other reasons for the visit for all (inpatient, outpatient, or non-patient) services. | |||
Diagnosis Coding | Inpatient | Outpatient/ Non-Patient | ICD-10-CM Official Guidelines |
Principal Diagnosis | |||
The condition determined after study to be chiefly responsible for admission of the patient to the hospital for care | Form Locator 67 | Not applicable | Section I, II: General Coding, Chapter-Specific, Selection of Principal Diagnosis and Present on admission |
Other Secondary Diagnosis | |||
Secondary diagnosis Complications and comorbidities (coexisting conditions) | Form Locator 67A-Q | Form Locator 67A-Q | Section I, III: General Coding, Chapter-Specific, Reporting Additional Diagnoses and Present on admission |
Admitting Diagnosis | |||
The major most significant reason the patient is admitted | Form Locator 69 | Not applicable | Section I, II: General Coding and Chapter Specific |
Patient’s Reason for Visit Diagnosis | |||
The major most significant reason for the outpatient visit | Not applicable | Form Locator 69 | Section I, II, IV: General Coding, Chapter-Specific and Diagnostic Coding, and Reporting for Outpatient Services |
External Cause of Injury | |||
External causes of the injury or illness | Form Locator 72a-c | Form Locator 72a-c | Section I: General Coding and Chapter-Specific Note: Guidelines for reporting external causes vary by payer. |