Coding Systems
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Appendix C Coding Systems The CPT-4 Coding System The ICD-9-CM Coding System for Physician Services for Hospitals1 Two widespread systems for codifying medical diag- The diagnosis-related groups (DRGs) used by Medi- noses and procedures exist in the United States: the care’s prospective payment system to categorize Physicians’ Current Procedural Terminology, Fourth patients for reimbursement purposes are based on a Edition (CPT-4), which codes procedures performed coding system known as ICD-9-CM. This system has by physicians, and the International Classification of two parts, The first and largest part is a comprehensive Diseases, Ninth Revision, Clinical Modification (ICD- list of diseases with corresponding codes. It is com- 9-CM), which codes hospital diagnoses and procedures patible with the World Health Organization’s (WHO’s) (9,188). list of disease codes, maintained for statistical pur- CPT-4 is a detailed list of five-digit codes for physi- poses, and is updated along with the WHO list every cian services, organized according to organ systems, 10 years. The second part of ICD-9-CM contains pro- that was developed (and is maintained) by the Amer- cedure codes. These are independent of the disease ican Medical Association (AMA). It was initially de- codes and are not directly based on an international veloped to facilitate physician reporting on claim system, although in the past they have been revised forms, and Medicare recently began requiring that concurrently with the disease codes. The National Cen- physician bills be based on a version of this system. ter for Health Statistics is the official WHO coding CPT has undergone numerous expansions, and the liaison in the United States, but the development and number of codes increased from 2,084 in 1966 to 7,040 maintenance of the American version of ICD has his- in 1985 (182). torically been a cooperative effort of representatives These codes may be clarified with modifiers under from a variety of governmental agencies and profes- certain circumstances. For example, the CPT-4 man- sional organizations (70). The codes have historically ual states: been infrequently updated, and until very recently [Certain procedures are a combination of a physician there was no established formal procedure for interim component and a technical component. When the phy- addition of codes or assignments of new diseases and sician component is reported separately, the service procedures to existing codes. In late 1985, as a result may be identified by adding the modifier ‘-26’ to the of the dilemmas and uncertainties arising out of coding usual procedure number or the service may be reported and DRG classification, a formal ongoing coding rec- by use of the five digit modifier code 09926 (10)]. ommendations task force, jointly chaired by the Na- This reporting procedure is the mechanism through tional Center for Health Statistics and Health Care which a radiologist, for example, may get paid a Financing Administration and including representa- “professional component only” charge for interpret- tives of the major interested organizations, was estab- ing an X-ray in a hospital and a total charge (includ- lished (50 FR 24374). ing an implicit or explicit “technical fee”) for an office- The ICD-9-CM codes are organized according to based X-ray, where the equipment is owned by the organ system (circulatory system, digestive system, physician. etc. ), with additional sections for subjects such as Because CPT-4 is entirely under the aegis of AMA infectious diseases and accidental injury. Diseases are and is updated annually, the advent of extracorporeal shock wave lithotripsy (ESWL) created no structural difficulties for this coding system. A new code to rep- I Port Ions ot th]> w( t ion are exerpted trom L I S ~’(~ngre~i, Ott Ice 01 TM h- nolog}r” Assessment, Nfdicares Prospe( t]~’e [’a~’ment S}’5tem Sfrategjes for resent ESWL performed by a physician, 50590, has E\r~luat{ng Cost Qual)f}, ,]rrd ,tfecf]cal Te(hnolog}’,” ~>~A-H-202 ~\l’a\hlng- been created. ton, I )C U S (l)vt,rnment I)nntmg Of t]ce, October I 985 I 94 95 assigned three-digit codes, with fourth and occa- table C-1 .—ICD-9-CM Codes Relating to sionally fifth digits available to allow more specificity. Urinary Stones For instance, hereditary anemia is code 282. Sickle- cell anemia, one type of hereditary anemia, is code Diagnostic codes: 592 Calculus (stone) of kidney and ureter 282.6, and the particular form called sickle-cell/Hb-C 592.0 Calculus of kidney disease is further specified as code 282.63. The proce- 592,1 Calculus of ureter dure codes are organized in a fashion similar to the 592.9 Urinary calculus, unspecified disease codes, except that maximium specificity is 594 Calculus (stone) of lower urinary tract 594.0 Calculus in diverticulum of bladder reached at four digits rather than five. Table C-1 lists 594.1 Other calculus in bladder some ICD-9-CM codes relating to urinary stones. 594.2 Calculus in urethra The process of DRG assignment depends on both 594.8 Other lower urinary tract calculus the diagnosis and procedure codes. The code for the 594.9 Calculus of lower urinary tract, unspecified principal diagnosis places the patient in a major diag- Procedure codes: nostic category and indicates which of several DRGs 55 Operations on kidney 55.0 Nephrotomy and nephrostomy might be appropriate. The code for the principal pro- 55.01 Nephrotomy (includes removal of stones cedure (or its absence) is used to determine whether from kidney) the appropriate DRG is a medical or a surgical one. 55.02 Nephrostomy Surgical DRGs generally have higher reimbursement 55.1 Pyelotomy and pyelostomy rates than medical ones. The final choice of DRG then 55.11 Pyelotomy (includes removal of stones from renal pelvis) depends on the specific procedure performed, the pa- 55.12 Pyelostomy tient’s age, and the presence or absence of coexisting 55.9 Other operations on kidney diseases and complications. 55.99 other The ICD-9-CM coding system, designed for clinical 56 Operations on ureter 56.0 Transurethral removal of obstruction from ureter and statistical purposes, presents several problems and rend pelvis when used as a basis for reimbursement (70,80,164). 56.2 Ureterotomy (includes removal of ureter stone First, if inaccurate or inadequate coding was frequent through incision) when the DRGs were designed, many hospital cases 57 Operations on urinary bladder may have been inaccurately classified. If this is the 57.0 Transurethral clearance of bladder 57.1 Cystotomy case, the DRG weights may consequently be inaccurate 57.19 Other cystotomy (includes removal of blad- themselves. Second, some medical conditions can be der stone through incision) described by more than one diagnostic code (80). Al- 58 Operations on urethra though any of several diagnoses may be technically 58.0 Urethrotomy (includes removal of stone in urethra through incision) correct, their associated codes lead to different DRGs 58.6 Dilation of urethra (includes removal of calculus with different weights. without incision) A third major concern regards the procedure codes. 59 Other operations on urinary tract Procedures utilizing new technologies may not be 59.9 Other operations on urinary system 59.95 Ultrasonic fragmentation of urinary stones appropriately described by any of the current codes, 59.99 Other and confusion about which code to use can lead to wide variation in DRG assignment. The code that seems most applicable may lead to an apparently inappropriate DRG; conversely, a DRG with an appar- ently appropriate reimbursement rate may be based tal Activities help to reduce confusion and promote on codes entirely unfitting to the new technology. coding uniformity, Major problems of coding assign- Coding consultants at the American Hospital Associa- ment are now the responsibility of the newly organized tion and the Commission on Professional and Hospi- task force. 59-9{)1 () - 86 - 5 : QI 3.