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Clinical Coding Audit Methodology


A pre-audit questionnaire regarding details of the organisation of clinical coding services in the UHB is completed by the Clinical Coding Manager prior to the site visit.


A list of Finished Consultant Episodes (FCEs) is randomly generated from the Patient Episode Database for Wales (PEDW) – the national database of Admitted Patient Care dataset activity. PEDW is managed and maintained by Digital Health and Care Wales (DHCW).


The episodes audited are limited to an episode length of ten days or less.


Staff at the Health Board are required to provide the auditors with access to the written case note records associated with the requested FCEs.


The locally assigned classification codes are audited against national clinical coding standards using the information available in the patients’ case notes and relevant electronic systems.


Attention is also paid to the quality of patient case notes documentation being used by the coders and auditors, in order to assess their impact on the assignment of codes.


The clinical coding record for each episode is generated from the Health Board’s clinical coding encoder software and a copy attached to the relevant set of case notes.


The auditors then assess the locally coded data against the National Clinical Coding Standards and the Welsh Clinical Coding Standards using ICD-10 and OPCS 4.9 classifications. The audit is carried out according to the current NHS Digital audit methodology.


Codes are audited as one of 4 types:

  • Primary Diagnosis codes (i.e. the main condition treated);

  • Secondary Diagnosis codes (including External Cause Codes and Morphology Codes);

  • Primary Procedure codes;

  • Secondary Procedure codes (including Chapter Z site codes).


Any errors are assigned to an Error Type according to the current NHS Digital audit methodology, which specifies the exact nature of the error. This information is then tabulated to calculate the statistical information required.


The errors are of two general types – non-coder errors and coder errors. Non-coder errors are those errors identified as being due to a factor external to the individual coder, such as an encoder system which automatically re-sequences codes, or a local coding policy which instructs the coder to assign codes in a way which contravenes national standards. Coder errors are errors in the coding made by the coder themselves.


For statistical reasons, and due to the discretion required in determining the relevance of a code to an episode, those error types where coding staff have assigned more codes than the auditor deems relevant (i.e. ‘over-coding’) are not counted as errors when calculating the error percentages. However, the numbers of these errors are reported and examples given for information and training purposes.


The recommended minimum percentage of correct codes are:

  • 90% for Primary Diagnosis and Primary Procedure

  • 80% for Secondary Diagnosis and Secondary Procedures


The Accredited Clinical Coding (ACC) exam also stipulates a minimum requirement of 90% accuracy for all clinical coding staff sitting the National Clinical Coding Qualification (NCCQ) exam. Furthermore, the above targets are consistent with the requirements set out in the NHS England Information Governance Toolkit requirement 505 (attainment level 2) and audits of coded data carried out by NCS auditors on clinical coding staff in NHS England.


Case notes which do not contain the episode to be audited are marked as ‘Unsafe To Audit’ (UTA), removed from the sample, and replaced.