OPCS-4

There is currently no Chapter I. Nor are there any codes beginning with an "I".

Whilst there is no Chapter O, codes beginning with an "O" can be found in OPCS-4. These were added to chapters when all the available 3-character code blocks were exhausted, but further classifications were needed. They are also referred to as "overflow codes", and are located at the end of the related chapter. When indexing a procedure or intervention that is classified to an O-code, the letter denoting the chapter the code is found in is given in parentheses after the code. For example: O04.- Embolisation Artery Aneurysmal Transluminal Percutaneous NEC (L).[11]

OPCS-4 is an alphanumeric nomenclature, and uses a four character code layout; similar to that found in ICD-10. The first character is always a letter. With the exception of the O-codes mentioned above, the letter indicates the chapter the code is from. The second, third and fourth characters are always numbers. A full stop (.) separates the third and fourth characters. Also, unlike ICD-10, there are no three character codes within OPCS-4.

Although OPCS-4 is used to classify procedures and interventions, and ICD-10 classifies diagnoses; their chapters do not correlate. That is to say; Chapter A of OPCS-4 is not used to classify treatments for conditions in Chapter I of ICD-10.

The introduction gives a brief guide on using OPCS-4, and defines some abbreviations; for example NEC (Not Elsewhere Classified).

This is the main bulk of the index, and contains the mechanism of looking up codes within the tabular list.

Terms are indexed in a What, Where, How method. For example, oesophagogastroduodenoscopy is trailed via Examination (the What), Gastrointestinal Tract Upper (the Where), Endoscopic Fibreoptic (the How).[12]

This list of surgical eponyms, contains common NHS procedures that may also be known by the surgeon, team or institution that developed the method or device used. For example, the Birmingham hip resurfacing and the Thompson Hemiarthroplasty.

Care must be taken when using trailing via Section II for two reasons:

1. The eponyms given are based on the original description, of the original procedure. If a modified version of the procedure was performed, for example a modified Akin osteotomy, or if the operation has been performed in conjunction with another procedure, e.g. Akin and Scarf osteotomies, the W15.6[13] code given in the index may not be correct.
2. Only a single term is used to index the eponyms, i.e. Birmingham rather than Birmingham hip resurfacing.[14] This means that care must be taken where the same eponym has been used more than once. For example, Thompson has four separate entries that apply to different procedures: Thompson's lymphoedema correction, cemented Thompson hemiarthroplasty, uncemented Thompson hemiarthroplasty, and Thompson's quadricepsplasty

This section of the Volume II contains an alphabetical list of common abbreviations and their definitions. For example, ECMO - Extracorporeal Membrane Oxygenation.[15]

As there are few instances where the abbreviation has been used more than once, and medical language is liable to change; descriptors are given to clarify all abbreviations. For example, SST could stand for Serum Skin Test or Short Synacthen Test.[16]

This section of Volume II is a single page glossary that defines suffixes that are used throughout the classification. For example, -otomy.

The National Clinical Coding Standards OPCS-4 is a reference book on how to use the classification, and provides guidance through examples. It is initially supplied to novice coders who attend a standards course run by a CCS approved trainer. Whilst each revision to OPCS-4 sees the issue of a new manual; any updates or corrections are issued electronically, and the onus is on the coder to update them by hand.

Prior to OPCS-4.7, and the move of maintenance responsibility to NHS Digital, the standards book was known as the Clinical Coding Instruction Manual.

Minor changes and coding advice for both ICD-10 and OPCS-4 are disseminated through the ICD-10 and OPCS-4 Classifications Content Changes. Until March 2022 this publication was known as The Coding Clinic, which was initially issued as a printed newsletter. Then, in 2012, the format was switched to a single, compendium-like electronic publication.

Maintained by the Department of Health's (DH) Payment by Results team; the High Cost Drugs List is a catalogue of drugs licensed for use in the NHS that are excluded from the Payment by Results (PbR) tariff.

Issued annually - even in years with no revision to OPCS-4 - the list consists of the generic names of certain drugs next to the relevant OPCS-4 code. The guidance section of the list states that it is down to the clinical staff to use the generic instead of brand names.

The Chemotherapy Regimens List, also issued by the DH Payment by Results team, is for the coding of administration of antineoplastic drugs. Organised alphabetically, the list contains adult and paediatric chemotherapy regimens used in the NHS. Drug trials are excluded as they are usually financed by the trial's commissioner, for example a pharmaceutical company or cancer charity.

The National Clinical Coding Standards OPCS-4 and both of the DH lists are issued to coders via Terminology Reference Data Update Distribution Service (TRUD)