One doctor's opinion

Advantages of SNOMED over ICD

By Raymond Simkus, MD

The International Classification of Diseases or ICD is the only medical terminology system that most doctors know; all doctors in Canada use this for billing purposes. Unfortunately, when it comes to clinical use, ICD is a flawed system. Doctors often complain that they cannot find the diagnosis they want because ICD is designed for after the fact coding and not for collecting diagnoses when the diagnosis is still uncertain.

The problems go much deeper than that. Typically EMR and billing vendors deliver ICD in a raw state with its very long and obtuse descriptions. ICD was designed to collect diagnosis data for statistical purposes. Health records professionals in hospitals are trained to use this system and they also know about searching with exclusion and inclusion criteria. Most medical offices have not had any training in ICD and are less sophisticated in its use.

If you look for ‘lung cancer’ you’ll get frustrated because all you’ll find is ‘malignant neoplasm of the trachea, bronchus and lung’ which makes it seem (to some) that the patient has three different tumours. Doctors spend many years learning exact names but then can’t find them in ICD when all they want is to record something quickly.
Here’s another example. ’Henoch-Schonlein purpura’ would typically get recorded as ‘rash’. With a full ICD9-CM listing you can find the correct code but ‘anaphylactoid purpura’ and other distinct conditions are assigned the same code. This is not useful from a clinical perspective.

There are more problems with applications using ICD, some annoying but others more serious than that. Some software enforces a particular ordering of words so that entering “ankle fracture” in a search will not find ‘fracture of ankle’. The user should be able to do a Google-style search where the order of the words doesn’t matter. A search capability that permits parts of words, so that ‘pur hen’ returns ‘Henoch- Schonlein purpura’, is even better. Inflexible and limited search engines could be fixed easily by their vendors.

A different kind of problem relates to the age of ICD9; it was released in 1976 and does not include commonly used diagnoses such as ‘acute coronary syndrome’ and ‘impaired glucose tolerance’.

Coding is required because free text descriptions won’t work. Spelling errors and multiple descriptions for the same concept would cause problems. Fortunately, a system called SNOMED (Systemized Nomenclature for Medicine) has been developed over the past 40 years and it is the most comprehensive terminology of clinical terms in existence. It was designed for physicians to use at the point of care and not for trained coders.

It has a hierarchical structure and built-in relationships so that users can see that ‘Henoch-Schonlein purpura’ is a vasculitis rather than a platelet disorder. SNOMED recognizes that different terms may exist for a given concept and provides synonyms along with what is called a ‘preferred term’. Older terms can be replaced by more modern terms but links are maintained to the older term.

Much of the early development of SNOMED was carried out in Canada by Dr. Roger Cote in Sherbrooke, Quebec but today it is owned by an international consortium of 12 countries, including Canada, the US, the UK and Australia. There is a new release every six months.

The EMR I am using now allows me to toggle between ICD and SNOMED. There are many occasions where I can’t find what I want in ICD but I find it right away in SNOMED. ICD is still needed for billing but SNOMED can be used for the problem list, indications for prescriptions, and virtually everything else.

Several years ago, a Canada Health Infoway project examined a number of systems. SNOMED was found to be appropriate for over 20 of the 24 clinical information groups that were studied. No other system was found to be adequate for more than one or two of the 24.

There has been competition between ICD and SNOMED in the past but today it is recognized that their functions are complimentary. ICD11 is currently under development and it is being designed to be integrated with SNOMED. This means that diagnoses captured using SNOMED will be used to feed the systems using ICD11.
It takes a considerable amount of effort to record clinical data. It would be satisfying if physicians could code what they know and the resulting data could be used for multiple purposes during the patient’s lifetime.

Dr. Ray Simkus is a primary care physician in Langley, BC. He has worked as a consultant for Canada Health Infoway and the BC Ministry of Health.

Posted March 4, 2010