Coding for infectious, neoplastic, and endocrine conditions

There are a number of conditions that require specific instructions for diagnostic coding. These conditions are described in the following sections.

Coding complications of care

A complication from medical care generally requires additional procedures or services for a patient, but often the complication is not mentioned as part of the diagnostic statement; this can result in reduced reimbursement. It is important to review the medical documentation to determine whether a complication exists and to code the complication in addition to the diagnostic statement. Keep in mind, not all conditions that occur during or after medical care or surgery are classified as complications. Two criteria must be met: a cause-and-effect relationship must be established between the care provided and the condition, and the documentation must indicate that the condition is a complication, such as postprocedural hemorrhage.

Coding infectious and parasitic diseases

Multiple diagnostic codes are needed to code infectious or parasitic diseases. The first code identifies the disease or condition (e.g., throat infection), and the second identifies the organism causing the disease (e.g., enterovirus). The second code can be found in the Tabular List in Chapter 1. The basic coding principles for using either combination or multiple codes apply throughout this section of the ICD-10-CM.

Coding organism-caused diseases

The two-step process of coding organism-caused diseases begins with the affected anatomic site. In the case of a throat infection caused by an enterovirus, you should first assign the diagnostic code for throat infection or pharyngitis. In the Tabular List, code J02.8 Acute pharyngitis due to other specified organisms is accompanied by the following Use additional code note: “Use additional code (B95–B97) to identify infectious agent”. In the Tabular List, the B95–B97 category/block (found in Chapter 1) is titled Bacterial and Viral Infectious Agents. Starting with code B95, search for the code that specifies enterovirus; this happens to be code B97.1 Enterovirus as the cause of diseases classified elsewhere.

Note that code B97.1 requires a fifth character; however, no other information is provided by the medical record. Therefore, you can assign code B97.19 Other enterovirus as the cause of diseases classified elsewhere as the final organism code.

Coding Human Immunodeficiency Virus (HIV) Infection and Acquired Immunodeficiency Syndrome (AIDS)

To correctly code HIV infection and AIDS, it is essential to first understand the descriptions of the codes available. The key is whether the patient has symptoms.

• HIV: This only indicates that the virus is present.
• AIDS: AIDS is a syndrome; a syndrome is defined as a “group of symptoms occurring together.” AIDS is the manifestation of signs or symptoms that can occur as a result of HIV infection.

Never code a patient as having HIV infection unless it is clearly documented as confirmed. Probable and suspected cases are never coded; instead, the signs and symptoms present should be coded. If a patient is seen for an HIV-related condition, the principal diagnosis should be B20 Human immunodeficiency virus [HIV] disease, followed by additional diagnostic codes for all reported HIV-related conditions.

Remember that strict restrictions are placed on the disclosure of medical information about patients with HIV infection or AIDS. Make sure the patient has signed the appropriate release of medical information form before any disclosures are made to third parties.

Coding neoplasms

A neoplasm, or new growth, is coded by the site or location of the neoplasm and its behavior. The Table of Neoplasms is located just after the Alphabetic Index in the coding manual. This table lists the ICD-10-CM codes for neoplasms by the anatomic site in alphabetic order. Six possible code numbers exist for each anatomic site, depending on whether the neoplasm is malignant or benign, exhibits uncertain behavior, or is of an unspecified nature. In the Table of Neoplasms, malignant neoplasms are categorized into three separate subclassifications: Malignant Primary, Malignant Secondary, and Ca in situ (carcinoma in situ).

Terms defining malignant neoplasm sites

• Malignant Primary: Identifies the originating anatomic site of the neoplasm. A primary malignancy is defined as the original site or sites of the cancer.
• Malignant Secondary: Identifies sites where the primary neoplasm has metastasized (spread). A secondary malignancy is defined as a second location to which the cancer has spread from the primary location.
• Ca in situ: Carcinoma in situ is defined as the absence of invasion of surrounding tissues. Tumor cells are undergoing malignant changes but are still confined to the point of origin, without invasion of surrounding normal tissue. The Ca in situ column is used only if the provider documents that precise terminology.

Most coding decisions on malignant neoplasms are between the primary and secondary classifications. Other terms are used in the following cases:

• In situ is used only when the diagnostic statement contains that exact phrase.
• Unspecified is used only when no pathologic study has been done, and the neoplasm is still described with a term such as tumor or growth.
• Uncertain is used when the pathologic study has been done, but it cannot be determined whether the neoplasm is malignant or benign.

Definitions of benign, uncertain behavior, and unspecified nature neoplasms

• Benign: The growth is noncancerous, nonmalignant, and has not invaded adjacent structures or spread to distant sites.
• Uncertain Behavior: The pathologist is unable to determine whether the neoplasm is benign or malignant.
• Unspecified Nature: Neither the behavior nor the histologic type of neoplasm is specified in the diagnostic statement.

Six steps for coding neoplasms

The following steps can help determine the most specific and accurate diagnostic code for a neoplasm. These steps can be used in addition to the basic diagnostic steps:

1. In the Table of Neoplasms, find the site (anatomic location) of the neoplasm.
2. Determine, from the documentation, whether the neoplasm is malignant or benign.
3. If the neoplasm is benign, select the correct column in the table by reviewing the diagnostic statement.
4. If the neoplasm is malignant, select the column in the table that best fits its behavior: Malignant Primary, Malignant Secondary, or Ca in situ.
5. Link the appropriate column to the appropriate row.
6. Check the code shown in the table with the code in the Tabular List to make sure it complies with the guidelines, conventions, and instructional notations of the latter.

The ICD-10-CM manual always provides additional information, definitions, and guidelines for coding neoplasms in the Tabular List, just as it does for all other diseases, illnesses, and injuries.

Coding for diabetes mellitus

Diabetes mellitus (DM) is classified as type 1 or type 2. Patients with DM type 1 develop the disease because the pancreas is unable to produce insulin. In individuals with DM type 2, the pancreas has become unable to maintain the level of insulin the body needs to function, or the person has developed target cell resistance to insulin.

The diabetes mellitus codes are combination codes. This means that they include the type of diabetes mellitus, the body system affected, and the complications affecting that body system. Use as many codes within a particular category/block as necessary to describe all the complications of the disease. These codes should be sequenced according to the reason for a particular encounter. Assign as many codes from category/block E08–E13 (Diabetes Mellitus) as needed to identify all the patient’s associated conditions.

Diabetes mellitus and the use of insulin

In the ICD-10-CM, the primary codes for diabetes mellitus (E08–E13) do not include whether the individual is using insulin. Therefore, if insulin use is documented in the health record, a second code is required: Z79.4 Long term (current) use of insulin.

Code Z79.4 should not be assigned if insulin is given temporarily during an encounter to bring the blood glucose level under control in a patient with DM type 2.

Gestational diabetes

Gestational, or pregnancy-induced, diabetes can occur during the second and third trimesters of pregnancy in women who were not diabetic before pregnancy. Gestational diabetes can cause complications in the pregnancy similar to those of preexisting diabetes mellitus. It also puts the woman at greater risk of developing diabetes after the pregnancy. Codes for gestational diabetes are in subcategory O24.4 Gestational diabetes mellitus and should be used with a code from subcategory O24.4. The codes under subcategory O24.4 include diet controlled (O24.410) and insulin controlled (024.414). If a patient with gestational diabetes is treated with both diet and insulin, only the code for insulin control is required.

No other code from category O24 Diabetes mellitus in pregnancy, childbirth, and the puerperium should be assigned.

Code Z79.4 Long-term (current) use of insulin should also be assigned with codes from subcategory O24.4 if the patient is being treated with insulin.

An abnormal glucose tolerance level in pregnancy is assigned a code from subcategory O99.81 Abnormal glucose complicating pregnancy, childbirth, and the puerperium.