ICD-9-CM is the Clinical Modification of the World Health Organization's International Classification of Diseases used for diagnostic coding in the United States. ICD-9-CM codes are required under HIPAA for reporting patients' conditions in both the inpatient and outpatient settings. Codes are made up of three, four, or five numbers and a description.
Two volumes of ICD-9-CM are used for diagnostic coding: the Tabular List (Volume 1) and the Alphabetic Index (Volume 2). The Alphabetic Index is used first in the process of finding a code. It contains an index of all the diseases that are classified in the Tabular List. The codes themselves are organized into seventeen chapters according to etiology or body system and are listed in numerical order in the Tabular List. A code category consists of a three-digit grouping of a single disease or a related condition. Subcategories have four digits to show the disease's etiology, site, or manifestation. Further clinical detail is supplied by fifth-digit sub-classifications. V codes and E codes are supplementary classifications for encounters for reasons other than illness or injury and for the external causes of illnesses or conditions. Volume 3 of ICD-9-CM classifies inpatient procedures that are billed by hospitals.
The conventions used in ICD-9-CM must be observed to correctly select codes. Notes provide details about conditions that are either excluded or included under the code. A symbol is used to show a fifth-digit requirement. The abbreviation NOS (not otherwise specified or unspecified) indicates the code to use when a condition is not completely described. The abbreviation NEC (not elsewhere classified) indicates the code to use when the diagnosis does not match any other available code. Parentheses and brackets indicate supplementary terms. Colons and braces indicate that one or more words after the punctuation must appear in the diagnostic statement for the code to be applicable. Codes that are not used as primary appear in italics and are usually followed by instructions to code first underlying disease or use an additional code.
Once ICD-9-CM codes for inpatient stays have been assigned and sequenced, each code must be assigned an indicator that identifies whether the condition was present on admission (POA). Y (for yes) is reported if the condition was present. Other indicators are N (no) if the condition was not present on admission, U if the presence of the condition on admission is unknown, and W if the presence of the condition on admission is clinically undetermined. Some codes, mostly V and E codes, are exempt from reporting the present on admission indicator, and the indicator is 1 or left blank (on paper claims).
HCPCS is the overall title of the two HIPAA-mandated outpatient procedural code sets, Level I (CPT) and Level II (HCPCS). CPT, a publication of the American Medical Association, contains the most widely used system of codes for outpatient medical, diagnostic, and procedural services. CPT codes have five digits and a description. HCPCS codes are supply codes made up of five characters beginning with a letter followed by four numbers. Updated HCPCS/CPT codes are released annually; current codes must be used.
CPT contains six sections of Category I codes, Evaluation and Management, Anesthesia, Surgery, Radiology, Pathology and Laboratory, and Medicine, followed by the Category II and Category III codes, nine appendixes, and an index. The index is used first in the process of selecting a code; it contains alphabetic descriptive terms for the procedures and services contained in the main text. The codes themselves are listed in the main text and are generally grouped by body system or site or by type of procedure.
Each coding section begins with section guidelines, which discuss definitions and rules for the use of codes, such as for unlisted codes, special reports, and notes for specific subsections. When a main entry has more than one code, a semicolon follows the common part of a descriptor in the main entry, and the unique descriptors that are
related to the common description are indented below it. Seven symbols are used in the main text: (a) • (a bullet or black circle) indicates a new procedure code; (b) <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073520896/577306/Ch4_Triangle1_Ch_Summary.JPG','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a> (a triangle) indicates that the code's descriptor has changed; (c) <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073520896/577306/Ch4_Triangle2_Ch_Summary.JPG','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a><a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073520896/577306/Ch4_Triangle3_Ch_Summary.JPG','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a> (facing triangles) enclose new or revised text other than the code's descriptor; (d) + (a plus sign) before a code indicates an add-on code that is used only along with other codes for primary procedures; (e) the symbol <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=png::ss::/sites/dl/free/0073520896/577306/Untitled3.png','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif">ss (26.0K)</a>ss next to a code means that conscious sedation is a part of the procedure that the surgeon performs; (f) a <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073520896/577306/Ch4_o_slash_Ch_Summary.JPG','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a> indicates that the code cannot be modified with a -51 modifier; and (g) a <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073520896/577306/Ch4_Spark.JPG','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a> is used for codes for vaccines that are pending FDA approval.
A CPT modifier is a two-digit number that may be attached to most five-digit procedure codes to indicate that the procedure is different from the listed descriptor, but not in a way that changes the definition or requires a different code. HCPCS modifiers are a different set of modifiers that contain either two letters or a letter with a number. Like CPT modifiers, they provide additional information about services, supplies, or procedures. Only a limited number of CPT and HCPCS modifiers are approved for hospital outpatient use.
HCPCS has an index and a listing of codes by alphabetic chapter. Chapters cover various supplies, such as durable medical equipment and drugs.
The basic four-step process medical coders follow to assign correct ICD-9-CM and HCPCS/CPT codes is (a) identify the diagnosis (diagnoses) and/or procedures to be coded; (b) locate the term in the index of the code set; (c) verify the code selection in the main listings of the code set; and (d) sequence multiple codes for correct billing.
The code sets that are associated with inpatient versus outpatient billing for hospital services are:
