Sex, gender, and medical dataBMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n735 (Published 19 March 2021) Cite this as: BMJ 2021;372:n735
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Thank you Rebecca Arthur for pointing this out and allowing us to clarify: the odd/even numbers for male and female patients applies in Scotland and we have reworded and hope this is now clear. Many thanks, Margaret McCartney
Competing interests: co-author
I found this article informative and sensible. I work in General Practice in an admin role and see multiple patient records every day, including those patients who have changed sex marker, pronoun, or legal name. We spend hours every month ensuring that the right people are called for cervical smears . Sex is hugely important to a patient’s records but System One is just not up to the job of ensuring the correct data is held (nor, I suspect, is any of the other systems used within the NHS). At least it uses the word sex, unlike our local hospital’s records, which records everything as gender.
I was confused by the reference in the article to “NHS numbers being biologically coded” as my experience with those numbers is that they appear to be randomly allocated. When I checked with the authors, I found that in fact what was quoted was actually referring to the Scottish CHI numbers, which indeed are biologically coded (how very sensible!) But this inaccuracy makes a bit of a mockery of that entire paragraph of the article. This is disappointing, as it makes the article’s premise far less credible, in my opinion.
Competing interests: No competing interests
Thank you for publishing this article which raises important issues about data integrity and protection around the attribute “sex” in NHS data systems.
As the authors state that “Sex and gender are not synonymous.” Sex, relates to biology - male or female. This is a fact about a person which is observed at birth (in most cases without ambiguity or difficulty) and recorded, in a binary fashion into a baby’s NHS number and their medical record. This fact about a person that does not change. However these records are now corrupted.
Gender can mean a number of different things which are not consistent or synonymous with each other..
1. A synonym for sex
2. The broad patterns of behaviour and appearance of the two sexes
i) The clothing and appearance norms associated with either sex
ii) Being perceived as a particular sex
iii) Wishing to be perceived as a particular sex
iv) Making an effort through appearance to appear as a particular sex
4. Social roles
i) The traditional social roles and expectations of behaviour of the sexes
ii) Wishing to be treated as a particular sex
iii) The extent to which someone conforms to traditional social roles
5. Self expression/identity
i) A means of self- expression
ii) An internal feeling of being a particular “‘gender’” (or both or neither)
i)The words used to refer people by sex (e.g. him/her, Mr, Ms)
ii)The words a person uses to refer to themself
iii)The words a person wishes other people to use to refer to them
iv) The words other people spontaneously use to refer to someone
Basic principles of data management are that each field or attribute should be clearly defined and contain only that information.
Healthcare providers and the NHS should hold accurate, reliable information about patient's sex as a basic minimum.
At the moment they do not. There is no single data attribute that records that I am female (and not in fact a male person who identifies as female and has asked to have their record changed).
More than ten years ago the NHS recognised the need for clear systems for recording biological sex and making sure it was not conflated with social gender. They carefully set up a system of data and definitions which could deal with both.
The data standard for the CUI written in 2009 explained:
“The term ‘Gender’ is now considered too ambiguous to be desirable or safe… ”
The data standard set out definitions for patient “sex” and “current gender” and warned:
“Users may confuse the terms current gender and sex, or assume that they are synonymous. Therefore, it is essential that all NHS applications display and explain current gender and sex terminology and values in a clear and consistent manner.”
The data standard set out in detail how to keep these two characteristics separate and unconfused, and how to design computer interfaces to ensure that sex data was captured (with social gender as an optional extra). It also set out potential consequences of not adhering to these standards including:
- The patient is given the wrong treatment as a result of a failure to identify the patient correctly.
- The patient is given the wrong treatment as a result of a failure to match the patient correctly with their artefacts (samples, letters, specimens, X-rays, and so on).
- The patient is given the wrong treatment as a result of a failure in communication between staff, or staff not performing or checking procedures correctly.
- The patient is categorised with a value that cannot be utilised by any other systems.
- The patient is categorised incorrectly from a legal perspective.
- The patient is categorised incorrectly from their perspective.
However despite establishing the basis for meeting these principles this system was not implemented. The current NHS data dictionary differentiates, "phenotypic sex" (as observed by a clinician) and "patient stated gender", but in practice “male” and “female” are recorded only against gender and the phenotypic sex field typically remains empty.
Policies to allow patients to change their registered "gender" are now embedded across the NHS.
The GMC tells doctors to change a patient’s sex/gender as recorded on medical records on request. This does not require any medical diagnosis, anatomical changes or a legal gender recognition certificate. 
Public Health England tells GP surgeries to change a patient’s’ recorded sex/gender on their medical record at any time, without requiring diagnosis or any form of gender reassignment treatment. They are given a new NHS number and previous medical information must be "gender neutralised" and transferred into a newly created medical record. They will be sent screening appointments (e.g. for cervical smear tests or prostate cancer screen) according to their new gender (i.e. invitations to attend the wrong screenings). 
Gender (self identified as male or female) is held by the Patient Demographic Service (PDS) for matching rather than clinical purposes. But it has recently been removed from the API because of sensitivity of people who identify as non binary and do not wish to be identified by their sex.
This approach shows the way forward. Sex should not be confused with gender identity, or any other of the myriad definitions of gender. Accurate information on everybody's sex should be held in their NHS record but it should only be disclosed or displayed when it is needed and should not be used for matching purposes.
The authors state that "sex and gender should not be used interchangeably". In fact data quality risks mean that "gender" should not be used as an attribute at all, because it is undefined and invites confusion.
Aspects of social gender such as titles, name used, and preferred pronouns can be recorded in other fields to facilitate social interaction. Transgender identity may be recorded.
Given that the law allows people to change their legal sex, a field may be needed where people's legal sex is recorded, without changing the record of their biological sex (since this, in fact, has not changed and it destroys day integrity for everyone if the field can contain either biological or legal sex).
If someone has a diagnosis or medical treatment such as hormones or surgery to change the appearance of their sex, this of course should be in their medical record.
Greater clarity about definitions, privacy, confidentiality and data protection would allow people to keep their sex private in situations where it is no one else's business but maintain the integrity of medical records. In NHS systems this would need to include a general system of not displaying the last digit of NHS numbers on screen.
Data protection principles apply to everybody and currently the NHS (along with the Passport Office and DVLA) are failing in these principles by requiring information about individual's sex, but then processing it in such as way (mixing it in a category with self declared gender) that the data is corrupted.
As the ONS case over the census highlighted by the authors shows, there will be legal challenges. The Digital Identities Trust Framework being developed by DCMS is also an opportunity to fix the problem of data corruption of the sex attribute.
The NHS should establish a task force to understand the corruption of sex data across medical records and establish a plan to fix it.
 NHS. 2009. Sex and Current Gender Input and Display User Interface Design Guidance https://webarchive.nationalarchives.gov.uk/+/http:/www.isb.nhs.uk/use/ba...
Competing interests: No competing interests
It is disappointing that the BMJ has chosen this as an editorial. The authors are not Gender Identity Specialists, and this editorial is the latest in line of number of letters and articles co-authored by Professor Bewley and Dr McCartney over the past few years where they have taken a stance which is against the consensus of Gender Identity Specialists with little to no evidence to support their position.
The lack of expertise of the authors is glaringly clear in the editorial itself. They start by saying that sex relates to “the gametes, chromosomes, hormones, and reproductive organs”, and then go on to argue that natally assigned sex should be recorded on all NHS systems so “relevant information about biological sex” is available for research and service delivery. But someone who is a trans woman may or may not have had hormonal treatment; she may or may not have had gender affirmative surgery. It is extremely likely that she has XY chromosomes, but even that is not an absolute certainty. Which of those is the “relevant information about biological sex”? They provide three references for “avoidable harm” that can happen when sex specific laboratory reference ranges are used for people whose gender but not “biological sex” is recorded. However, the first reference does not mention the topic.  The second states “once individuals have commenced gender-affirming hormone therapy, the reference range of the affirmed gender be reported” (with the exception of PSA and cardiac troponin).  The third does flag up the potential for harm in inaccurately calculated eGFRs, but rather than an automatic reversion to calculation on natal gender assignment, an individualised approach based on muscle mass is suggested.  The important part of “biological sex” (both to patient and researcher) in these cases is more complex than natally assigned sex. As they mention, sex differences in drug metabolism certainly exist; however, a large number of these are hormonally mediated, meaning again that in those cases a trans person on hormones would be categorised correctly under their recorded gender.  Their example of not having data on the Covid-19 outcomes trans people on hormonal treatment would be utterly unchanged by having natally assigned sex recorded, as that gives no clue as to whether or not the person is on hormonal treatment.
They seem to be worried about trans people being on inappropriate screening registers – but trans women on hormonal treatment will develop natural breast tissue, and should attend breast screening in the same way as any other woman, so getting that automated invite is entirely appropriate for them.  The obvious answer to the issue is having flexibility in the system to respond to those who do not fit into their norms (which of course includes, for example, cis women who for whatever reason do not have a cervix).
There is still a great deal of research to be done into transgender health, and women’s health is still all too often seen as just a deviation from a male norm. However, neither of these are served by over-simplification. “Sex” is a combination of multiply interacting things which may not fit into neat boxes, whether naturally (intersex conditions) or through human intervention (hormonal treatment for trans people). To say that a trans person’s natally assigned gender is their sex is (for many people) to say that the chromosomal always trumps the hormonal, and it is definitely not clear that this is the case. Exactly what is needed to be recorded and extracted for the best research and service delivery is probably not yet certain.
However, I have to suspect given the previous publications of two of the authors that this is not a topic which is raised in good faith. Rather, raising the spectre of trans people contaminating research outcomes gives another avenue for fearmongering about trans people and advancing a particularly chromosomally essentialist view of sex.
Saying this, I have no intention to shut down discussion and debate around trans health. But the reality is that in the British medical press, there is little debate; rather a small number of clinicians and academics who are critical of mainstream gender services and critical of the main organisations representing transgender people are published again and again. I am sure that the authors of the article will respond that they only have the health and wellbeing of the trans community at heart. Looking at a group of (apparently) cisgender, non-experts who mobilise their professional credentials to gain a platform for views which many trans people would consider harmful, the trans community can be forgiven for doubting how sincere this is.
1. Hord L, Medcalf K. Trans people’s experience of healthcare in England. Transforming Futures Partnership, 2020. https://www.transformingfuturespartnership.co.uk/healthcare
2. Cheung AS, Lim HY, Cook T, et al. Approach to interpreting common laboratory pathology tests in transgender individuals. J Clin Endocrinol Metab2021;106:893-901. doi:10.1210/clinem/dgaa546
3. Fernandez-Prado R, Ortiz A. A sudden decrease in serum creatinine and estimated glomerular filtration rate: clinical implications of administrative gender assignment in transgender persons. Clin Kidney J 2019;13:1107-8. doi:10.1093/ckj/sfz152. pmid:33391757
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5. Berner, J. I’m trans or non-binary, does this affect my cancer screening? Cancer Research UK, 2019 [cited 20 March 2021] https://www.cancerresearchuk.org/about-cancer/screening/trans-and-non-bi...
Competing interests: No competing interests