AANS Neurosurgeon | Volume 28, Number 4, 2019


Medical Coding: An Evolution by Punctuated Equilibrium

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In what seems like a past life, I was a student of Stephen Jay Gould. He was a passionate lecturer and a larger-than-life character; after all, he was both in our classroom and on the Simpsons. He spoke about Darwin as if he was a childhood friend and was unwavering in his descriptions that Darwin was a genial man. He seemed absolutely certain of this. He taught us about punctuated equilibrium in the evolution of species; relative stagnation with interspersed period of enormous change. This seems true in medical coding, as well.  Why do have this alphabet soup of codes?  Does it serve any real purpose?

Coding Origins
Medical coding has been around since the late 16th century. In those days, “coding” diagnosis was motivated by the need to  track mortality during periods of plague. The London Bills of Mortality were weekly fatality statistics (1592-1595; 1603) designed to monitor burials during plague breakouts. In 1629, the causes of death were listed but in 1819, these were no longer being published. For 200 years, coding diagnoses to keep track of burial plots seemed good enough (1).

Diagnosis Coding Change
In 1937, the World Health Organization (WHO) breathed new life into the publication of death statistics. WHO developed an international list of causes of death, which evolved into the International Classification of Diseases (ICD). The ICD system gained worldwide recognition by 1977. Subsequently, the National Center of Health Statistics (NCHS) expanded the now familiar ICD to include clinical diagnoses, not just causes of death. From this point onward, changes in health care philosophies have led to massive changes in coding. For example, with ICD-9, there were 13,000 codes with many “other” and “non-specified” codes, while with ICD-10, there are 68,000 codes and the elimination of many of the non-specific codes (2).

Procedural Code Evolution
Procedural coding has followed a similar pattern to diagnostic coding. The Current Procedural Terminology (CPT) is part of the Healthcare Common Procedure Coding System (HCPCS) Level I. The entire system is copyrighted and maintained by the American Medical Association (AMA). The HCPCS Level II pertains to supplies, medicines and other services during a patient visit. Evolution of technology and medicines has resulted in dramatic changes to HCPCS Type II. Punctuation of equilibrium happened in 1983 when the Centers for Medicare & Medicaid (CMS) adopted the CPT system. Soon after, CPT became standard for all commercial payors. By 2000, the Transactions and Code Sets Final Rule mandated that CPT, HCPS Level II and other modifiers be the standard national medical code set (3).

Technological, social and philosophical pressures have triggered relatively large changes in coding, with evolution taking us from statistics on burials to anatomically precise coding that is integrated in modern electronic medical records, epidemiological databases and health care quality initiatives. Seemingly always behind and trying desperately to catch up with the times, medical billing and coding is a dynamic process.  Where will this punctuated equilibrium take us next?

1. https://en.wikipedia.org/wiki/Bills_of_mortality

2. hiacode.com

3. mb-guide.org/history-of-medical-coding.html

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