Possible or probable, so what is the difference?
I've struggled with these two definitions, really tried to get my head around them both.
First off I used Dictionary.com
Possible:
1. that may or can be, exist, happen, be done, be used, etc
2. that may be true or may be the case, as something concerning which one has no knowledge to the contrary
Probable:
1. likely to occur or prove true
2. having more evidence for than against, or evidence that inclines the mind to belief but leaves some room for doubt.
3. affording ground for belief.
When it comes to prescription medications causing adverse events, the World Health Organisation (WHO) use "causality categories" and define possible and probable as thus...
Possible:
• Event or laboratory test abnormality, with reasonable time relationship to drug intake
• Could also be explained by disease or other drugs
• Information on drug withdrawal may be lacking or unclear
Probable:
• Event or laboratory test abnormality, with reasonable time relationship to drug intake
• Unlikely to be attributed to disease or other drugs
• Response to withdrawal clinically reasonable
• Rechallenge not required
In essence both words have two possible outcomes yet both have different meanings.
I am going to focus on the case of Cheryl Buchanan here and her correspondence with citalopram makers Lundbeck. Citalopram is better known as Cipramil in the UK and Celexa in the US. ( Forest Laboratories)
Cheryl has been at loggerheads with Lundbeck regarding the death of her baby girl. Cheryl made the heart wrenching decision to abort her fetus at 23 weeks because she had been told that scans had detected a series of anomalies in her unborn child, namely...
- Diaphragmatic hernia or eventration
- Long bone immobility
- Cystic hygroma
- Unilateral cleft hand
- Microgynathia
Cheryl had been taking Lundbeck's citalopram prior and during her pregnancy. She wrote a guest post for my blog back in 2013 and has since been trying to get answers from the Danish pharmaceutical giant Lundbeck.
Lundbeck carried out an assessment of Cheryl's claims and forwarded their findings to the MHRA.
Lundbeck, as far as I am aware, also use the World Health Organisation "causality categories".
Here's what they found.
(Foetal death in utero) - drug related - possible
(Pulmonary hypoplasia) - drug related - possible
(Diaphragmatic hernia) - drug related - possible
(Hand deformity) - drug related - possible
(Skin laxity) - drug related - possible
(Skin swelling) - drug related - possible
(Drug exposure in utero) - drug related - possible
Fig 1.
Fig 2. **Initial reporting from Lundbeck to the MHRA did not give any indication for Cheryl's fetus developing Pulmonary hypoplasia**
Fig 3. **Updated assessment by Lundbeck sent to the MHRA regarding a possible connection between citalopram related Pulmonary hypoplasia**
Sometime later Cheryl wrote to Lundbeck and asked if citalopram could cause birth defects?
Here's the reply from Lundbeck's Dr Andrew Jones, Medical Director, Medical Department.
"...there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects over the background risk in general population (i.e. of mothers not taking citalopram). "It was at this point that I wrote to Dr Jones to ask him if this was a personal opinion or an opinion of Lundbeck. He replied...
Dear Mr Fiddaman,
I confirm that this is the position of Lundbeck.What I am struggling with here takes me back to the definitions of possible and probable.
Lundbeck assess Cheryl's case and write to the MHRA with their findings. They tell the MHRA that the birth defects (listed above) are possibly drug related. Using the WHO criteria this means that...
The defects could just be coincidental to Cheryl's "drug intake" or
The defects may possibly have been caused by "disease or other drugs" or
The Information Cheryl provided Lundbeck "may be lacking or unclear"
Let's now take a look at the position of Lundbeck regarding citalopram use and birth defects. Remember, it was their own Dr Jones that told me that the following was the position of Lundbeck...
"...there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects over the background risk in general population (i.e. of mothers not taking citalopram). "
So, how do we categorize the position of Lundbeck. Are they suggesting that it's possible that there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects?
Are they saying it's probable that there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects?
Or are they saying they are certain that there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects?
Back to the WHO criteria again.
Certain:
• Event or laboratory test abnormality, with plausible time relationship to drug intake
• Cannot be explained by disease or other drugs
• Response to withdrawal plausible (pharmacologically, pathologically)
• Event definitive pharmacologically or phenomenologically (i.e. an objective and specific medical disorder or a recognised pharmacological phenomenon)
• Rechallenge satisfactory, if necessary
Lundbeck have done nothing more than open the door for debate when sending information back to the MHRA.
Where the mother is concerned they have quite literally slammed the door on her face by telling her that their position is there is no evidence to indicate that usage of citalopram in pregnancy increases the risk of birth defects over the background risk in general population.
Why would they (technically) tell the MHRA otherwise?
Why would Lundbeck tell the MHRA that it was possible that citalopram caused the birth defects in a mother's fetus but tell that same mother something completely different?
I'm confused by it all. Is the WHO criteria merely a set of probabilities with at least two possible outcomes? If so, it doesn't really tell us much does it?
Is the WHO criteria not as stringent as they think and each category open for debate?
What we basically have is two opposing statements of reality intertwined.
The third statement of 'certainty' by Lundbeck to Cheryl Buchannan being an ultimatum, in essence, "our drug does not cause birth defects", forgetting or purposely failing to add that they told the MHRA otherwise.
It's certain that Cheryl Buchanan aborted her fetus at the age of 23 weeks because, she was told, the chances of survival were minimal due to a series of internal defects.
My money is on citalopram being the cause of those defects.
Any good lawyers in the UK?
Bob Fiddaman.
Back Stories
Citalopram Birth Defects (Guest Post)
Are Lundbeck Luring Pregnant Mothers With a Red Apple?
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