Requirement vs. Dependency

Question from Krista Lilly on behalf of the Content Team's Editorial Panel. I'll put it on the agenda for next meeting but perhaps we can get a headstart here.

I see the definition of requirement is "something wanted or needed" or "something essential to the existence or occurrence of something else" (like required competencies for a job). While dependence is defined as "the quality or state of being dependent" (dependent being "determined or conditioned by another" or "relying on another for support" or "affected with a drug dependence") or "drug addiction".

I can hardly see anyone using alcohol "requirement" instead of alcohol dependence for the alcohol addicts. Dependence on drugs, tobacco and alcohol has a specific clinical meaning of "addiction" as opposed to "use" (which is chronic like dependence but where the patient can still stop for long periods) and "abuse" (which means excessive use at a specific point in time without necessarily an addiction). So there I would not accept we add alcohol requirement as synonym, I think we would all agree it would sound utterly bizarre in a medical record to say that a patient requires alcohol and it would be confusing to say he requires drugs because people can require drugs to stay alive and that has nothing to do with an addiction. It is actually a dependence to the drug when you need absolutely to take a pill to stay alive but when we say drug dependence in a clinical setting, we mean addiction. So indeed there is maybe a clarification to bring that dependence on machines mean the machine is required in order to allow you to live while dependence on drug means you're addicted not that this drug is needed for you to survive (setting aside the question of withdrawal is you do not take it).

Requires would in French translate to the fact that the oxygen or machine is needed. However it is not as strong as dependence on oxygen or on a machine. As in the dictionary definition required is something wanted or needed, it can be required for comfort. Dependence on oxygen for one has stronger legal implications of the support being essential to life. A patient may require temporary O2 at home which will or won't be reimbursed depending on the clinical use-case, but 02 dependence means the patient has gotten a specific medical long term 02 convention with the mutuality that allows him/her to have fully reimbursed 02 because without it he/she'd die. 

I'll ask around to our clinicians how the feel about the distinction between 02 requirement and 02 dependence. I feel they'll say one isn't the same as the other no more then respiratory deficiency is the same as respiratory failure.

As to the 698532002 |Equipment requirement (finding)| family, those are things that the patient needs but that he can live without. It's about orthodontic material. You can't say you're dependent to your orthodontics device can you? 

The children of 105501005 |Dependence on enabling machine or device (finding)| are true dependence for machines that support life itself except the dependence to walking stick or wheelchair but those are needed to support basic life needs of moving around so here I would certainly keep dependence and not use requirement.

I have trouble with the meaning of 716366009 |Requires continuous home oxygen supply (finding)|, as opposed to 60651000119103 |Dependence on continuous supplemental oxygen (finding)|. I would say the first is a bad duplicate of the second or that we must clearly define that "requires" is for short term 02 home treatment in acute diseases that you can still manage at home (like in young covid patients when our hospitals were full) while dependence is some long terme and essential to life need. I'm not sure the distinction of dependence on supplemental 02 at home is needed. It is more the notion of 02 dependence at rest versus during exercice that is clinically relevant. There we should see if 89201000119106 |Dependence on supplemental oxygen when ambulating (finding)| and 702546009 |Requires oxygen therapy during exercise (finding)| are not duplicates. I would not think so as ambulating isn't exercice. Exercise is more then "ambulating" but as exercise isn't essential to life, I do not see really a clinical use-case where one would prescribe 02 in order to allow the performance of an exercice. The only use of this concept I might see is maybe in cardiologic testing, when you want to determine what is the limitation in an effort test, one might maybe add 02 to determine that the effort limitation is of respiratory nature and not of cardiac nature... I'll ask my cardiologist colleague.

I agree with Marie-Alexandras explanations. I only have a few comments:

• Does ‘require’ perhaps include the meaning that the healthcare service needs to provide a service as in for instance 716366009 |Requires continuous home oxygen supply (finding)| (meaning the service of supplying oxygen to the patient’s home)? This however is, not very well described in the attributes and parents of the concept…
• Some descriptions in SCT use the term ‘need for’, ‘needs’ or ‘need of’ to express similar meaning as requires e.g. 722013004 | Increased need for rest (finding) | or 400986007 | Needs help with cooking (finding) |, but perhaps without the above service included.
• I think you can be ‘ dependent on your orthodontics device’ for instance to eat.

Camilia, at least in French, and it looks to me also in SNOMED CT, orthodontic devices are only the devices used for misaligned teeth not the dental prosthesis. So you are not dependent on an orthodontic device to eat, only to have a better occlusion or a nicer smile.

Here is the opinion I received from one of our Dutch speking Belgian terminologist/doctor on how he'd render the concepts in Dutch.

• 698532002 |Equipment requirement (finding)| and 12 subtypes =>requirement betekent hier volgens mij “vereist” 
• 716366009 |Requires continuous home oxygen supply (finding)| => requires betekent hier volgens mij “afhankelijk van”
• 702546009 |Requires oxygen therapy during exercise (finding)| => requires betekent hier volgens mij “afhankelijk van”
• 105501005 |Dependence on enabling machine or device (finding)| and 26 subtypes => dependence betekent hier volgens mij “afhankelijk van”
• 716366009 |Requires continuous home oxygen supply (finding)| => requires betekent hier volgens mij “afhankelijk van”
• 60651000119103 |Dependence on continuous supplemental oxygen (finding)| => dependence betekent hier volgens mij “afhankelijk van”
• 191816009 |Drug dependence (disorder)| and 118 descendants =>dependence betekent hier volgens mij “verslaafd aan”
• 66590003 |Alcohol dependence (disorder)| and 6 subtypes => dependence betekent hier volgens mij “verslaafd aan”

Het onderscheid tussen “requires” en “dependence” geeft mijns inziens ook wel een gradatie van de graad van afhankelijkheid. “Requires” zou je ook kunnen vertalen als “heeft nodig” en “dependence” als het sterkere “afhankelijk van”.

His conclusion is that there is a gradation for him between requires = needs this, and dependence = really depends on this for life. And dependence can also means addicted to depending on the context of use.

We discussed this in our translation team and had trouble putting our finger on the difference. 'Dependence' translates literally to 'afhankelijkheid', but most of the examples with current FSN 'requires' could well be translated to 'afhankelijkheid van ...'. Especially in nursing, it's common to say a patient is 'afhankelijk van rolstoel' (dependent on wheel chair), while of course they only need one to get about, not to stay alive. It sounds very odd to my own ears, but that's jargon for you...

At present we do have a lot of translations of 'requirement' to 'nodig'. 'nodig' is also used as translation for the English terms 'needed' and 'due' (the latter is a bit dubious). So, are there three shades of meaning for needed, required, and dependent? Or are there maybe two meanings needed and dependent, where 'required' kind of sits in the middle?

Krista Lilly We discussed your question at our meeting today. Camilla Wiberg Danielsen , Maria-Cornelia Wermuth , Marie-Alexandra Lambot , Krista Kart I hope I've summarised it properly; if not feel free to correct me!): 

We definitely see a difference between 'requirement' and 'dependency', but it is hard to describe and the current content in SNOMED is not entirely consistent with the distinction. Our thoughts:

• Dependency seems to be a statement, whereas requirement implies some necessary action. Requires shows an intention of the subject, dependency implies some external agent that causes the dependency. The difference seems to lie in a quality of the patient, who either asks for something (requirement), or needs something to function (dependency).
• Dependency can also refer to some legal convention, where the patient can e.g. require oxygen to recover faster, or depend on oxygen for their next breath.
• Requires may be the same as 'needs', with requires being the more polite way to phrase it; however, 'being in need of' would be closer to dependency.

Krista Lilly Please note that you have to look for other word forms also: require, requires, requirement, needs, need of, need for, dependency and perhaps more that we have not found yet.