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The evolution of CPT® code conventions

In 1970, the (AMA) American Medical Association (AMA) implemented a five-digit code structure (00100-99607) for its Current Procedural Terminology (CPT). However, the codes are not meaningless, random numbers; each section and subsection of CPT are restricted to a subset of the codes, and “grouped” or related appropriately, as seen in the example below (in particular, note 10060 and 10061).


10021-10022 General

10030-19499 Integumentary System

10030-11646 Skin, Subcutaneous, and Accessory Structures

10030-10036 Introduction and Removal

10040-10180 Incision and Drainage

10040 Acne surgery

10060 Incision and drainage of abscess; simple or single

10061 Incision and drainage of abscess; complicated or multiple


11000-11047 Debridement


11719-11765 Nails


Because of this limitation, there were not 99,999 CPT codes, as there were many “spaces” left “between” codes (i.e., many of the numbers between 00001 and 99999 were not used). Over the last 47 years, AMA has often found itself “running out of codes” available in a particular section or subsection for new procedures, so the following workarounds have been put in place:

  • Alpha characters were allowed in the fifth code position
    • In 2004: Category III codes ending with T (temporary codes for emerging technologies), e.g.,
      0085T Breath test for heart transplant rejection
    • In 2005: Category II codes ending with F (used for supplemental tracking for performance measurement), e.g.,
      0503F Postpartum care visit (Prenatal)
    • In 2015: Multianalyte Assays with Algorithmic Analysis (MAAA) codes ending with M (in Appendix O), e.g.,
      0004M Scoliosis, DNA analysis of 53 single nucleotide polymorphisms (SNPs), using saliva, prognostic algorithm reported as a risk score
    • In 2017: Proprietary laboratory analyses codes ending with U, in the Pathology and Laboratory section (this category comes after code 89398), e.g.,
      0001U Red blood cell antigen typing, DNA, human erythrocyte antigen gene analysis of 35 antigens from 11 blood groups, utilizing whole blood, common RBC alleles reported 
  • In 2010, the AMA relaxed the rule about “grouping” or “relating” codes for similar procedures, and started using codes from a different “space” – known as resequencing.

“It is utilized to allow placement of related concepts in appropriate locations within families of codes regardless of the availability of numbers for sequential numerical placement.”

The 2018 release includes 314 resequenced codes (marked with # in CPT manuals). Examples are provided below.

    • Resequenced Code Example 1: Codes slightly “out of sequence” 
Out of Sequence  CPT Code  Description 
   21555   Excision, tumor, soft tissue of neck or anterior thorax, subcutaneous; less than 3 cm
 #  21552   Excision, tumor, soft tissue of neck or anterior thorax, subcutaneous; 3 cm or greater
   21556   Excision, tumor, soft tissue of neck or anterior thorax, subfascial (eg, intramuscular); less than 5 cm
 #  21554   Excision, tumor, soft tissue of neck or anterior thorax, subfascial (eg, intramuscular); 5 cm or greater
    • Resequenced Code Example2: Codes significantly “out of sequence”
 Out of Sequence CPT Code  Description 
  82306   Vitamin D; 25 hydroxy, includes fraction(s), if performed
 #  82652   Vitamin D; 1, 25 dihydroxy, includes fraction(s), if performed
  82308  Calcitonin


Even with these two workarounds, the lack of available codes has resulted in extraordinarily long descriptions in the Molecular Pathology lab section (see table below) and very long descriptions in other sections.

CPT Code  Partial Description  Description Length  Number of Different Genes 
81400  Molecular pathology procedure, Level 1 (eg, identification of single germline variant …) … 2,539 67
81401 Molecular pathology procedure, Level 2 (eg, 2-10 SNPs, 1 methylated variant, ...) …  9,870  342
81402 Molecular pathology procedure, Level 3 (eg, >10 SNPs, 2-10 methylated variants, …) …  1,803  75
81403 Molecular pathology procedure, Level 4 (eg, analysis of single exons by DNA sequence analysis, ….) …  5,366  153
81404  Molecular pathology procedure, Level 5 (eg, analysis of 2-5 exons by DNA sequence analysis, …) …  10,593  271
81405 Molecular pathology procedure, Level 6 (eg, analysis of 6-10 exons by DNA sequence analysis, …) …  14,943  381
81406* Molecular pathology procedure, Level 7 (eg, analysis of 11-25 exons by DNA sequence analysis, …) …  16,894  422
81407 Molecular pathology procedure, Level 8 (eg, analysis of 26-50 exons by DNA sequence analysis, …) …  3,966  127
81408  Molecular pathology procedure, Level 9 (eg, analysis of >50 exons in a single gene by DNA sequence analysis) …  2,448  78

*The complete description for code 81406 takes almost four pages to display in the CPT manual, and there are over 17 pages of Molecular Pathology table to aid coders in selecting the correct code(s).

To illustrate, here’s the description for CPT code 81402, the shortest one of the above:

Molecular pathology procedure, Level 3 (eg, >10 SNPs, 2-10 methylated variants, or 2-10 somatic variants [typically using non-sequencing target variant analysis], immunoglobulin and T-cell receptor gene rearrangements, duplication/deletion variants of 1 exon, loss of heterozygosity [LOH], uniparental disomy [UPD]) Chromosome 1p-/19q- (eg, glial tumors), deletion analysis Chromosome 18q- (eg, D18S55, D18S58, D18S61, D18S64, and D18S69) (eg, colon cancer), allelic imbalance assessment (ie, loss of heterozygosity) COL1A1/PDGFB (t(17;22)) (eg, dermatofibrosarcoma protuberans), translocation analysis, multiple breakpoints, qualitative, and quantitative, if performed CYP21A2 (cytochrome P450, family 21, subfamily A, polypeptide 2) (eg, congenital adrenal hyperplasia, 21-hydroxylase deficiency), common variants (eg, IVS2-13G, P30L, I172N, exon 6 mutation cluster [I235N, V236E, M238K], V281L, L307FfsX6, Q318X, R356W, P453S, G110VfsX21, 30-kb deletion variant) ESR1/PGR (receptor 1/progesterone receptor) ratio (eg, breast cancer) IGH@/BCL2 (t(14;18)) (eg, follicular lymphoma), translocation analysis; major breakpoint region (MBR) and minor cluster region (mcr) breakpoints, qualitative or quantitative MEFV (Mediterranean fever) (eg, familial Mediterranean fever), common variants (eg, E148Q, P369S, F479L, M680I, I692del, M694V, M694I, K695R, V726A, A744S, R761H) MPL (myeloproliferative leukemia virus oncogene, thrombopoietin receptor, TPOR) (eg, myeloproliferative disorder), common variants (eg, W515A, W515K, W515L, W515R) TRD@ (T cell antigen receptor, delta) (eg, leukemia and lymphoma), gene rearrangement analysis, evaluation to detect abnormal clonal population Uniparental disomy (UPD) (eg, Russell-Silver syndrome, Prader-Willi/Angelman syndrome), short tandem repeat (STR) analysis

In the future, we can expect that:

  • The AMA will create additional codes that end with an alpha character
  • There will be descriptions as long or longer than that of code 81406 due to the explosive growth of new genetic/genomic tests
  • The number of resequenced codes will increase and may cause confusion for users and programmers (e.g., pick-list applications and code sorting)

CPT is an important terminology for healthcare. If you have questions regarding CPT or need help with terminology implementation or mapping, please contact us.

CPT Copyright 2016 American Medical Association. All rights reserved. CPT® is a registered trademark of the American Medical Association.