In order for coding standards to be consistently applied there are common principles for writing standards (ISO, 2016) (ISO, 2012) (ISO TC215 Health Informatics, 2019) (ISO TC215 Health Informatics, 2009).

man coding

These have been adopted considering work undertaken on code systems and classification development and include:

a) Use consistent terminology which is well defined
b) Apply rules consistently throughout all standards
c) Document the standard in a way that is easy to understand and apply, and examples should be informative not normative.
d) Indicate the rationale for the standard where appropriate to assist understanding and ongoing application in new situations as they arise.

The instructions in ACS 1902 Adverse Effects (Australian Consortium for Classification Development for ICD-10-AM Eleventh Edition, 2019) provide information about the coding of manifestations and external causes of adverse effects.

Australian Coding Standard 1902 Adverse Effects

‘Adverse effects of correct substances properly administered are classified according to the nature of the adverse effect.’

There is no other instruction (other than the need for an external cause to be used – which reinforces an existing standard), just an example.

Analysis of ACS 1902 Adverse Effects was undertaken by applying 4 principles of quality standards and data:

a) Use consistent terminology
The text “According to the nature of the adverse effect” – appears to be saying that the coder should code the manifestation e.g. rash. This is an example of use of inconsistent terminology in the standard where “manifestation” is commonly used, and a new phrase (the nature of the adverse effect) has been added for this standard.

b) Consistency across all coding and standards.
See ACS 1901 poisoning which has a different approach to ACS 1902

c) Document the rule in a way that is easy to understand.
Our interpretation of the standard written in a repeatable and actionable manner:

This method of explaining the standard has only one interpretation and applies to all examples of the situation, rather than being dependent upon an example. Examples should support the standard not be used to explain it or extend it.

d) Rationale
The rationale for this standard is that the manifestation together with the cause of injury code tells the whole story.

This is consistent with good data practice which does not mix the scope of concepts (Cimino, 1998) The concept of the injury is one thing, while the concept of the cause and place is another. Together these tell the whole story.

Coding Adverse Reactions in the UK

‘Where a reaction to a drug or medicine is not stated as being the result of proper or improper use, it is assumed to be the result of proper use and must therefore be coded as an adverse effect.’ (NHS Digital, 2019).

The rule appears to be:

a) If the injury is caused by a drug (whether adverse effect, intentional, accidental does not impact the coding)
Code the T code from the drug table as the first code in the injury code set
b) If there is a manifestation of the drug documented
This is also to be coded, sequenced after the drug injury T code.


  • T code injury for the drug
  • External Cause code
  • Manifestation of the poisoning.

Coding Adverses Reactions in the USA

The injury codes have been extended to indicate both the substance taken and the intent when taken. Additional external codes are not required (it is assumed this is because it is already covered in the injury code).

Instructions are provided on how to find the right code and to use as many codes as necessary to describe completely all substances.

Though it might be covered elsewhere in the Guidelines there is no instruction in this area of the guide on how to represent manifestations. (ICD-10-CM Official Guidelines for Coding and Reporting , FY 2020)

Final General Comment

In all cases each substance causing a reaction are coded. Otherwise the objective of coding this information seems to be differently represented in each country.

This is an excellent example of the need for a morbidity data collection information model where the scope of the data is defined according to the data elements used rather than relying on the sequence in which codes are entered to imply meaning.

This approach has been proven to improve data collection in EHRs rather than attempting complex pre-coordination of concepts in very open data elements.

More on this topic will come shortly in the GeHCo LinkedIn articles.

What do you think? Please comment below…


Adverse Effects: References

Australian Consortium for Classification Development for ICD-10-AM Eleventh Edition. (2019). ICD-10-AM/ACHI/ACS Eleventh Edition V1.0. Sydney.

Cimino, J. (1998, Nov). Desiderata for Controlled Medical Vocabularies in the Twenty-First Century.

Retrieved from US National Library of Medicine, National Institutes of Health

ICD-10-CM Official Guidelines for Coding and Reporting . (FY 2020). Retrieved from Coding Adverse Reactions the UK

ISO. (2012). Guidance for writing standards taking into account micro,, small and medium-sized enterprises’ needs. Geneva: International Organization for Standarization.

ISO. (2016). How to write standards. Retrieved from ISO

ISO TC215 Health Informatics. (2009). ISO/TR 123090:2009 Guidelines for terminology development organizations. Geneva: International Standardization Organization.

ISO TC215 Health Informatics. (2019). ISO 17115 Representation of categorial structures of terminology (CatStructure). Geneva: International Standardization Organization.

NHS Digital. (2019). National Coding Standards ICD-10-5th Edition. Leeds, UK: NHS Digital.