International Classification of Diseases Codes and their Use in Dentistry

Abstract

The deadline for replacing International Classification of Diseases, 9th edition (ICD-9) code sets with the newer ICD-10 code sets, used for the reporting of medical diagnoses and inpatient hospital procedures, was recently updated to occur at a date no sooner than October 1, 2015; with October 1, 2015 being the likely implementation date. The transition to ICD-10 is mandatory for all entities covered by the Health Insurance Portability Accountability Act (HIPAA). This review will provide a brief history of the development of ICD codes; provide an overview of ICD-9/ICD-9-Clinical Modification (CM) and ICD-10/ ICD-10-CM/Procedural Coding System (PCS) codes; provide information on the conversion of ICD-9-CM to ICD-10-CM/PCS codes; and provide information on the uses of ICD codes in dentistry in the United States.

The International Classification of Diseases and International Classification of Diseases - Clinical Modification (ICD-CM), more commonly referred to by the acronyms ICD and ICD-CM, respectively, are diagnostic tools used to code and classify diseases and health conditions that are recorded on health records and vital statistics (1). ICD and ICD-CM codes are used for epidemiologic purposes to monitor incidence, prevalence, morbidity, and mortality statistics for disease conditions in an internationally standardized manner (1). Additionally, these codes are used by hospitals to capture and retrieve clinical procedural information, for health management and reimbursement purposes, and to provide information that can help with resource allocation decisions (1). The deadline date for replacing the ICD-9 code sets used to report medical diagnoses and inpatient (inhospital) procedures by the newer ICD-10 code sets is scheduled to occur no sooner than October 1, 2015; with October 1, 2015 being the likely implementation date (2, 3). It should be noted that the previous compliance date was scheduled to go into effect on October 1, 2014; however, the Protecting Access to Medicare Act of 2014 was passed on April 1, 2014 to extend the date of compliance (2, 3).

The conversion to ICD-10 is a federal mandate by the Department of Health and Human Services (DHHS) for all entities covered by the Health Insurance Portability Accountability Act (HIPAA) in an effort to provide a greater level of diagnostic detail, thereby, ultimately leading to improved diagnostic quality and accuracy for reimbursements. HIPAA requires adopted standards to be used for the electronic data exchange of health care information. The change to ICD-10 does not, however, affect Current Procedural Terminology (CPT) coding for outpatient procedures and physician services.

This review aims to provide a brief history of the development of ICD codes; provide an overview of ICD-9/ ICD-9-CM and ICD-10/ ICD-10-CM/PCS (Procedural Coding System) codes; provide information on the conversion of ICD-9-CM to ICD-10-CM/PCS codes; and provide information on the uses of ICD codes in dentistry in the United States.

History of the International Classification of Diseases

Systematic disease classification can be traced back to the 1700's (4). In 1785, a physician named William Cullen published a document entitled Synopsis nosologiae methodicae, which classified several common diseases at the time (4). This classification scheme was used up until the early 19th century. However, William Farr, a medical statistician in the General Register Office of England and Wales, noted that Cullen's disease classification was outdated and recognized its limitations (4). Farr noted that several disease conditions were described by vague, non-uniform nomenclature (4). He recognized the advantages of a uniform statistical classification and nomenclature for diseases, and focused his studies on making more uniform disease classifications that could be used internationally and for statistical purposes (4). Farr's model of disease classification became the basis for the International List of Causes of Death, which would eventually merge with lists of diseases causing morbidity and ultimately form what is known today as the International Classification of Diseases (ICD) (4).

The ICD is a comprehensive list of diseases causing both morbidity and mortality that is presently used, and undergoes periodic revisions under the watch of the World Health Organization (WHO) (5). Currently, ICD-10 is used for the coding of mortality data on death certificates, while ICD-9 is used to code morbidity and inpatient hospital procedural data (1, 6). The conversion from ICD-9 to ICD-10 for the coding of morbidity and hospital procedural information is currently taking place as ICD-10 clinical and procedural codes will replace the former code set (7). In addition, revisions are underway for 11th Revision of the International Classification of Diseases (ICD-11) codes, which are being developed to be used with electronic health records and health information systems (8).

ICD-9 and ICD-9-CM

It is important to note the distinction between the two disease classifications that are currently used. The International Classification of Diseases (ICD) is used to classify mortality data from vital statistics (i.e. death certificates) (9). The similarly named International Classification of Diseases, Clinical Modification (ICD-CM) is used to classify morbidity data from hospitals, physicians' offices, and surveys; as well as inpatient hospital procedural information (9).

The 9th revision of the ICD occurred in 1975 (4). ICD-9 classified diseases into 17 main sections/chapters (10), and contained additional detail in the form of sub-categories and even more detailed subdivisions for certain disease conditions (4). ICD-9 was developed to be beneficial to individuals using the codes for statistical purposes by providing two codes for certain diagnostic terms: a code for the underlying disease and a code for the disease presentation in a specific organ/site (4, 10). ICD-9 was used for coding mortality data from 1979–1998 (11).

In 1979, the ICD -9 Clinical Modification (ICD-9-CM) was developed for use in the United States with input from clinicians, epidemiologists, and statisticians to classify morbidity information from hospital records and physician offices, as well as hospital procedural data (6, 12). ICD-9-CM is completely comparable to ICD-9 with some revisions such as the inclusion of more clinical detail where necessary (6, 12). Specifically, ICD-9-CM consists of three volumes: Volume I- numerical lists of disease code numbers in a tabular form; Volume II- an alphabetical index to disease conditions; Volume III- alphabetical index and tabular list classification for surgical, diagnostic, and therapeutic procedures (6, 12). ICD-9-CM codes are currently required for the reporting of morbidity diagnoses and hospital inpatient procedures under the HIPAA (12, 13).

ICD-9-CM codes will be used to code hospital diagnostic and procedural data until they are replaced when ICD-10-CM/PCS codes go into effect (7). According to the Centers for Medicare & Medicaid Services (CMS), there will be no exceptions or grace period once the new codes go into effect, and claims requiring the ICD-10-CM/PCS code will not be processed unless the proper codes are provided (7). It should be noted, that as was the case with ICD-9-CM, there is no mandatory requirement for reporting ICD-10-CM external cause codes (Chapter 20- External Causes of Morbidity) unless a new state or payer-based requirement is implemented (14).

The major force behind the replacement of ICD -9-CM is the fact that the code is very old and outdated, and therefore does not as closely align with current medical diagnoses and hospital procedures (14). ICD-10-CM/PCS will provide substantially greater detail that will better align with current medical practices (14). Many countries have already implemented ICD-10 into their medical systems, including: United Kingdom (1995), France (1997), Australia (1998), Germany (2000), and Canada (2001) (14).

ICD-10 and ICD-10-CM/PCS

The 10th revision of the ICD occurred in 1999 and is the current classification system used for the coding of mortality data (15). ICD-10 differs from its predecessor, ICD-9, in several important ways (Table 1). In general, ICD-10 contains substantially more detail on the disease conditions than ICD-9. For example, ICD-10 contains approximately 8,000 categories and 21 sections/chapters to classify causes of death compared to the approximately 5,000 categories and 17 sections/chapters that are found in ICD-9 (15). Additionally, an increasing number of subcategories exist for many disease conditions to provide more detail about the type and/or site of the disease (15). Another distinct feature of the ICD-10 code is the use of alphanumeric codes as compared to the all-numeric coding scheme used in ICD-9 (15).

Table 1.

Brief comparison of ICD-9 and ICD-10

	ICD-9 (ICD-9-CM)		ICD-10 (ICD-10-CM/PCS)
Dates effective	1979 – 1998 (ICD-9)	1979 – September 2014 (ICD-9-CM)	1999- Present (ICD-10)	October 1, 2015*- TBD (ICD-10-CM/ PCS)
Number of sections	17 Chapters       5,000 categories		21 Chapters       8,000 categories
ICD code features	All numeric		Alpha-numeric
ICD-CM(PCS) code features	Both diagnostic and hospital procedural information within ICD-CM ICD-CM (diagnostic)       3–5 digits       first digit is alpha or numeric       decimal is after the third digit ICD-CM (procedural)       3–4 digits       all digits are numeric       decimal is after the second digit		Separate code used for diagnostic and hospital procedure information ICD-CM       3–7 digits       first digit is alpha       second digit is numeric       digits 3–7 can be alpha or numeric       decimal is after the third digit ICD-PCS       7 digits       digits can be alpha or numeric       no decimal.
Key upgrades	Contained additional codes for underlying disease and disease presentation for certain diagnoses		Contains greater detail for disease conditions and ability to capture additional clinical information

^*At the time of article production, DHHS had planned to announce a required implementation date of October 1, 2015, but had not done so officially.

For clinical purposes, ICD-10 consists of both ICD-10-CM (a diagnostic classification system) and ICD-10-PCS (Procedural Coding System- a classification for procedures conducted) (16). As with ICD-9-CM, the new ICD-10-CM is the clinically modified classification system of ICD-10 that is used to code for morbidity data in the U.S., and was developed with input from statisticians, epidemiologists, and clinicians (16). It is completely comparable to the ICD-10 published by the WHO (16). Whereas ICD-9-CM contained codes for hospital inpatient procedures in addition to diagnostic codes, ICD-10-PCS is a separate coding classification system that will be required for hospital inpatient procedures at the time of implementation (17). ICD-10-CM/PCS improves upon its predecessor by providing more detailed medical information, and medical terminology and classification that better aligns with current medical practice (14). The increased level of detail allows for: more accurate measurement of health care services, more efficiency for reimbursement processing, improved surveillance, and better data for research and clinical decision making (14). Table 1 provides a summary comparison of the key features of ICD-9/ICD-9-CM and ICD-10/ ICD-10-CM/ PCS.

Looking towards the future, experts are currently providing input to develop ICD-11 codes that align with current medical practice and scientific knowledge (8). The WHO is inviting interested stakeholders to be involved in the revision of the code (8). An important feature of the ICD-11 code will be its compatibility with electronic health records and applications (8).

Converting from ICD-9-CM to ICD-10-CM/PCS

As previously mentioned, all providers that are covered by HIPAA will be required to use ICD-10-CM/PCS codes for diagnoses and hospital inpatient procedure transactions on (the likely implementation date of) October 1, 2015 (2, 3). Providers must ensure that their systems and procedures are in place to allow for the use of the clinical ICD-10 codes. The previous delays in the mandatory implementation date were made in order to provide ample time to ensure systems compliance. The conversion to ICD-10-CM/PCS will require providers to work with Information Technology (IT) staff/consultants, Electronic Health Record vendors, and support staff for practice management systems to ensure that the necessary IT software/infrastructure is in place for systems that will perform ICD-10 transactions (7).

CMS provides a website containing links to valuable documents and resources that can help providers in transitioning from ICD-9-CM to ICD-10-CM/PCS codes. This information can be found at: https://www.cms.gov/Medicare/Coding/ICD10/ProviderResources.html. CMS has also developed implementation handbooks with templates to assist providers with the transition from ICD-9 to ICD-10, which can be found at: http://www.cms.gov/Medicare/Coding/ICD10/index.html?redirect=/ICD10/05a_ProviderResources.asp. These handbooks, designed specifically for small hospitals, large provider practices, and small to medium provider practices, can be used as a reference for the transition process.

Additional resources for ICD-10-CM/PCS conversion are provided by: Health Resources and Services Administration- http://www.hrsa.gov/healthit/icd10/; American Health Information Management Association- http://www.ahima.org/downloads/pdfs/resources/checklist.pdf; and Workgroup for Electronic Data Interchange- http://www.wedi.org/topics/icd-10/, among others. It is recommended that all dental providers have a thorough understanding of how ICD-10-CM/PCS codes will impact their practice, and ensure that they have the necessary systems and procedures in place to be compliant well in advance of the implementation date. The resources listed above are intended as a starting point for information. Dental providers should contact the appropriate personnel if additional questions arise regarding the ICD-10-CM/PCS implementation and how it will affect their practice.

In addition to the resources listed above, several on-line conversion applications have been developed where health care providers, researchers, or other users of ICD codes can convert ICD-9 codes to the corresponding ICD-10 codes. For example, when the search term "ICD-9 to ICD-10 conversion tool" was used in the Google search engine, the first page of results yielded websites that contained conversion applications or mapping documents (Table 2). The styles of these conversion applications differ, and users are recommended to use the one that they are most comfortable with.

Table 2.

List of websites containing conversion applications or mapping documents for converting ICD-9 to ICD-10.

http://www.aapc.com/icd-10/codes/ http://www.icd10data.com/Convert http://seer.cancer.gov/tools/conversion/ http://www.icd10codesearch.com/ http://www.tdrdata.com/ipd/ipd_icdcodetools.aspx

ICD Codes in Dentistry

Dental providers have been required to provide ICD-9 diagnostic codes to medical carriers for claims for some time now. For purely dental procedures, however, the majority of dentists use the Current Dental Terminology (CDT) codes. The CDT, maintained by the American Dental Association, is a five-digit alpha-numeric system used for reporting dental services. These are used to record and report dental treatment and are usually updated once every five years. The use of CDT will not be impacted by ICD-10. The CDT became a standard HIPAA code set on August 17, 2000 and is now required to be used when submitting a HIPAA standard electronic dental claim for outpatient dental procedures (18). The code is used to accurately reflect dental treatment provided, and it is periodically revised to best-reflect current dental practice (18). Electronic submission of administrative transactions (for example, checking a patient's eligibility, filing a claim, receiving a remittance advice directly to a health insurance payer or through a clearinghouse, epidemiological studies, protocols, and decision support) now requires the use of electronic HIPAA transaction version 5010. The older version 4010 had been in use since 2003, but was upgraded to version 5010 on January 1, 2012.

After the ICD-10-CM/PCS effective date, if a reimbursement form requires a dentist to code for a specific diagnosis or a dentist performs procedures in an inpatient hospital setting, the ICD-10-CM/PCS code will be required (7). ICD-10-CM codes will also be necessary when a dentist bills Medicare for medically necessary dental procedures. Section 2 of the Medically Necessary Dental Care Act of 2011 states that dental services are "medically necessary" if they are performed in conjunction with a patient being treated for: prosthetic heart valve replacement, head or neck cancer, lymphoma, leukemia, or organ transplantation (19). Some examples of medically necessary dental treatments covered by Medicare for patients with the above conditions include: extraction of teeth before radiation therapy; management of mucositis, hemorrhage, and related side effects; and management of infections after transplantation (20). Furthermore, reimbursement from Medicaid for dental services that are covered for pregnant women or in conjunction with systemic disease conditions, such as diabetes will necessitate the use of ICD-10-CM codes (17, 21). Diagnoses for temporomandibular disorders, trigeminal neuralgia, and other oro-facial pain conditions can be found in the ICD-10-CM code, and dentists treating these conditions will also use these codes (22). Finally, dentists providing services in inpatient hospital settings will be required to use ICD-10-PCS codes.

Common ICD-10 diagnostic codes related to dentistry are presented in Table 3 (22). Figure 1 displays two examples of how ICD-10-CM dental codes compare to their corresponding codes in ICD-9-CM. The ICD-9-CM codes are listed for the diagnoses of dental caries on the pit and fissure and smooth surfaces. The corresponding ICD-10-CM codes expand upon the previous code by not only describing the location of the decay, but also describing the depth of the lesion (into enamel, dentin, or pulp). It is evident that the new code provides a greater level of detail that is more descriptive of the actual clinical diagnosis.

Table 3.

ICD-10 Code Description

K00	Disorders of tooth development and eruption
	Anodontia (K00.0)
	Supernumerary teeth (K00.1)
	Abnormalities of size and form of teeth (K00.2)
	Mottled teeth (K00.3)
	Disturbances in tooth formation (K00.4)
	Hereditary disturbances in tooth structure, not elsewhere classified (K00.5)
	Disturbances in tooth eruption (K00.6)
	Teething syndrome (K00.7)
	Other disorders of tooth development (K00.8)
	Disorder of tooth development, unspecified (K00.9)
K01	Embedded and impacted teeth
	Embedded teeth (K01.0)
	Impacted teeth (K01.1)
K02	Dental caries
	Arrested dental caries (K02.3)
	Dental caries on pit and fissure surface (K02.5)
	Dental caries on smooth surface (K02.6)
	Dental root caries (K02.7)
	Dental caries, unspecified (K02.9)
K03	Other diseases of hard tissues of teeth
	Excessive attrition of teeth (K03.0)
	Abrasion of teeth (K03.1)
	Erosion of teeth (K03.2)
	Pathological resorption of teeth (K03.3)
	Hypercementosis (K03.4)
	Ankylosis of teeth (K03.5)
	Deposits [accretions] on teeth (K03.6)
	Posteruptive colour changes of dental hard tissues (K03.7)
	Other specified diseases of hard tissues of teeth (K03.8)
	Disease of hard tissues of teeth, unspecified (K03.9)
K04	Diseases of pulp and periapical tissues
	Pulpitis (K04.0)
	Necrosis of pulp (K04.1)
	Pulp degeneration (K04.2)
	Abnormal hard tissue formation in pulp (K04.3)
	Acute apical periodontitis of pulpal origin (K04.4)
	Chronic apical periodontitis (K04.5)
	Periapical abscess with sinus (K04.6)
	Periapical abscess without sinus (K04.7)
	Radicular cyst (K04.8)
	Other and unspecified diseases of pulp and periapical tissues (K04.9)
K05	Gingivitis and periodontal diseases
	Acute gingivitis (K05.0)
	Chronic gingivitis (K05.1)
	Aggressive periodontitis (K05.2)
	Chronic periodontitis (K05.3)
	Periodontosis (K05.4)
	Other periodontal diseases (K05.5)
	Periodontal disease, unspecified (K05.6)
K06	Other disorders of gingiva and edentulous alveolar ridge
	Gingival recession (K06.0)
	Gingival enlargement (K06.1)
	Gingival and edentulous alveolar ridge lesions associated with trauma (K06.2)
	Other specified disorders of gingiva and edentulous alveolar ridge (K06.8)
	Disorder of gingiva and edentulous alveolar ridge, unspecified (K06.9)
K08	Other disorders of teeth and supporting structures
	Exfoliation of teeth due to systemic causes \(K08.0)
	Complete loss of teeth (K08.1)
	Atrophy of edentulous alveolar ridge (K08.2)
	Retained dental root (K08.3)
	Partial loss of teeth (K08.4)
	Unsatisfactory restoration of tooth (K08.5)
	Other specified disorders of teeth and supporting structures (K08.8)
	Disorder of teeth and supporting structures, unspecified (K08.9)
K09	Cysts of oral region, not elsewhere classified
	Developmental odontogenic cysts (K09.0)
	Developmental (nonodontogenic) cysts of oral region (K09.1)
	Other cysts of oral region, not elsewhere classified (K09.8)
	Cyst of oral region, unspecified (K09.9)
K11	Diseases of salivary glands
	Atrophy of salivary gland (K11.0)
	Hypertrophy of salivary gland (K11.1)
	Sialoadenitis (K11.2)
	Abscess of salivary gland (K11.3)
	Fistula of salivary gland (K11.4)
	Sialolithiasis (K11.5)
	Mucocele of salivary gland (K11.6)
	Disturbances of salivary secretion (K11.7)
	Other diseases of salivary glands (K11.8)
	Disease of salivary gland, unspecified (K11.9)
K12	Stomatitis and related lesions
	Recurrent oral aphthae (K12.0)
	Other forms of stomatitis (K12.1)
	Cellulitis and abscess of mouth (K12.2)
	Oral mucositis (ulcerative) (K12.3)
K13	Other diseases of lip and oral mucosa
	Diseases of lips (K13.0)
	Cheek and lip biting (K13.1)
	Leukoplakia and other disturbances of oral epithelium, including tongue (K13.2)
	Hairy leukoplakia (K13.3)
	Granuloma and granuloma-like lesions of oral mucosa (K13.4)
	Oral submucous fibrosis (K13.5)
	Irritative hyperplasia of oral mucosa (K13.6)
	Other and unspecified lesions of oral mucosa (K13.7)
K14	Diseases of tongue
	Glossitis (K14.0)
	Geographic tongue (K14.1)
	Median rhomboid glossitis (K14.2)
	Hypertrophy of tongue papillae (K14.3)
	Atrophy of tongue papillae (K14.4)
	Plicated tongue (K14.5)
	Glossodynia (K14.6)
	Other diseases of tongue (K14.8)
	Disease of tongue, unspecified (K14.9)

Figure 1.

Examples comparing of corresponding ICD-9-CM and ICD-10-CM codes.

Limitations of ICD Code use in Dentistry

Overall, ICD diagnostic codes are drastically underutilized in the dental profession. The enhanced level of detail in the ICD-10-CM/PCS codes provides an opportunity for both dentists and researchers to benefit from the analysis of the more detailed diagnostic information, however, the mandated use of these codes only apply to limited situations (see examples above). The regular reporting of diagnostic codes could potentially provide important clinical information that could be used by researchers for epidemiologic purposes. On a smaller scale, the regular use of diagnostic data could potentially provide private practitioners with beneficial information about the overall oral health status of patients in their practice. Additionally, the rationale for proposed treatment plans could be better conveyed to 3rd party entities if ICD diagnostic codes were recorded in addition to the CDT codes. As ICD diagnostic codes continue to become more detailed to better reflect current practice, the dental community should examine the potential benefits of regularly utilizing these codes to ultimately improve the delivery of oral health care to their patients.

CONCLUSION

It is the hope of the authors that this review was able to provide information and resources that providers can use to ensure that they will be compliant when ICD-10-CM/PCS codes go into effect. Additionally, examples of situations which would require dentists to use the ICD codes were provided, as well as examples of ICD codes that are used in dentistry for providers that may not be familiar with ICD codes and their use in dentistry. Providers should keep current on information regarding the ICD-10-CM/PCS compliance date, as this date has been delayed several times. If additional questions or details are required regarding the reviewed content, providers should contact the appropriate consultants, practice managers, or legal advisors as necessary.