COVID19 Questionnaires, PEM/PESE, and the Office for National Statistics

As our learners will know, there is limited data available on the prevalence of M.E/C.F.S in the UK and internationally. Much has been said about the opportunity Long Covid brings in terms of data collection and research opportunities. Stripy Lightbulb CIC strongly believes that the Office of National Statistics ‘COVID19 questionnaires’, that research Long Covid, could easily be adapted to include Post-Exertional Malaise/Post-Exertional Symptom Exacerbation (PEM/PESE – the key defining characteristic of M.E/C.F.S). We are not asking for additional M.E/C.F.S research, we are simply requesting ONE additional question be asked within the existing questionnaire. This would help get a better understanding of how many Long Covid patients have PEM/PESE, how many recover before the two year point, and how many with PEM/PESE are still sick at the 2 year point (most likely will have life-long M.E/C.F.S as only 5% ever recover after this point). This would be Long Covid research as Long Covid is an umbrella term for many different presentations of illness of which M.E/C.F.S is the greatest subset. It should be pointed out that PEM/PESE is NOT ‘fatigue’ and so this characteristic is not currently represented within this questionnaire. We have seen many questionnaires and surveys from other organisations that have said PEM/PESE is included within the ‘fatigue’ category. This is misrepresenting what PEM/PESE actually is. A person can have ‘fatigue’ and not have PEM/PESE.

Data, data, data!

We first contacted the Office for National Statistics on the 26th January 2022 – see email below.

26 January 2022 –

As a social entrepreneur tackling the social issue of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, I am writing to ask if you could increase the number of Long Covid-related questions in your Covid questionnaires.
Recent research has estimated that 46% of Long Covid patients meet the diagnostic criteria for M.E/C.F.S. There are now multiple research studies that state similar.
It would be really useful for ME/CFS research internationally to know at what point Long Covid patients start to meet the diagnostic criteria. It will also help to better uncover how many Long Covid patients are developing ME/CFS in each of the regions of the UK.
There is no diagnostic test for M.E/C.F.S. There are 7 indicators that patients must meet. I believe your questions could easily include these indicators. The key defining characteristic of ME/CFS is Post-Exertional Malaise – ‘Do your symptoms flare after physical or mental exertion both immediately and a few days afterward?’ would be a simple additional question that would flag PEM.
I look forward to hearing from you.
Best wishes,
Sally Callow

ONS reply – 27th January 2022

Dear Sally

Many thanks for getting in touch. We are currently considering additional survey questions relating to long COVID, including on PEM, and I have noted your very helpful suggested wording.

Kind regards,


Principal Statistical Methodologist

Office for National Statistics | Swyddfa Ystadegau Gwladol


This was an encouraging response and Stripy Lightbulb CIC waited to see if any changes would be implemented in subsequent ONS questionnaires.

I also emailed the ONS on 3rd February 2022 with this email –

3rd February 2022


As a social entrepreneur who is tackling the social issue of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome with education, I’m contacting you to see if the ONS could help to work out the prevalence in the UK.

The 250,000 statistic is well over a decade old and as we gain around 9000 patients every year (outside of the pandemic), the need to update this prevalence statistic is greater than ever.

I contacted you a week ago to ask if questions could be included within your Long Covid questions to determine how many have PEM – the hallmark characteristic of M.E/C.F.S. I was assured that this is something that the ONS is already working on. Great news! Thank you.

But I am now wondering if these same questions could be included within your more routine surveys in later years. For example, running a ‘wash-up’ of the pandemic survey in late 2023, would capture the number of people who have PEM in the wider population, not just those who have Long Covid-related PEM.

We need this, I am not sure if you are aware but cases of M.E?C.F.S are not recorded accurately for 2 reasons –

– Most GPs do not know what M.E/C.F.S is and under/misdiagnosis is common.

– Coding systems are confusing and M.E/C.F.S is often coded incorrectly

This is why, historically, prevalence has been estimated at between 0.20% to 1.03% of the population – depending on who was doing the research.

I believe the ONS could help us to get a much more accurate idea of how many people in the UK have PEM and as such are likely to have ME/CFS (would have to meet rest of the criteria too).

I hope you can help.

Best wishes,

Sally Callow

ONS response -17th February 2022

Dear Sally

Many thanks for your email. You are correct that we considering changes and additions to our long COVID data collection, including asking survey participants about post-exertional malaise.

Beyond the pandemic, we would need to identify a suitable survey vehicle for collecting data on symptoms associated with other conditions such as ME/CFS. Our long COVID data are collected on the Coronavirus Infection Survey (CIS), which has obviously been set up specifically to gather insights on COVID-19, and at present we don’t run any other surveys on population health more generally.

Have you considered making contact with NHS Digital, who run the Health Survey for England:   

Kind regards,


| Principal Statistical Methodologist

Office for National Statistics | Swyddfa Ystadegau Gwladol


Readers – we contacted NHS Digital, they will not be doing this research.


PEM/PESE was not added to the February/March/April/May/June COVID19 questionnaires and so I emailed again on 16th June 2022

16th June email to ONS – 

See email thread (emails included in this blog)
I have noticed that PEM was not included in your latest published research. Do you have a timeline of when this will happen? Or has a decision been taken to not include PEM in this data?
Best wishes,

Email response from ONS – 23rd June 2022

Hi Sally

Thanks for your email. It has not been possible to modify the survey questionnaire since the last update to the long COVID symptom list due to ongoing work to transition the survey to an online platform.

We would very much like to ask survey respondents with long COVID about their experience with PEM, but I can’t give you a timeline for when such a question could be added to the survey at this stage.

Kind regards,


| Principal Statistical Methodologist

Office for National Statistics | Swyddfa Ystadegau Gwladol

Freedom of Information Request

Stripy Lightbulb CIC decided to submit a Freedom of Information request to see what decisions had been taken internally at ONS regarding data collection on PEM/PESE. We received an FOI response on 19th July 2022.

See –


Questions must surely be asked as to why a question about one of the ‘common’ symptoms of Long Covid is not included on this important questionnaire. PEM/PESE is a symptom of Long Covid because half of Long Covid cases meet the diagnostic criteria for M.E/C.F.S. We believe that a deliberate decision must have been made to exclude this symptom/characteristic from the data collection.

This data would be supplementary to research estimates and would reinforce the anecdotal knowledgebase.

The M.E/C.F.S community need every bit of data available, that includes data on PEM/PESE amongst the Long Covid patient community.

This is a work in progress.

Sally Callow, Managing Director, Stripy Lightbulb CIC.

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