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Everything you ever Wanted to know About (Determining) Sex in Clinical Trials

Everything you ever Wanted to know About (Determining) Sex in Clinical Trials

The collection of data associated with sex or gender in a clinical trial isn’t as straightforward as we would initially think. In fact, it’s amazing just how confusing it can be. First off, there is the difference between sex and gender (no, I’m not talking about the differences between men and women, which would be a topic for another blog). According to the Merriam-Webster dictionary:

  • Sex is defined as either of the two major forms of individuals that occur in many species and that are distinguished respectively as female or male especially on the basis of their reproductive organs and structures
  • Gender is the behavioral, cultural, or psychological traits typically associated with one sex

So sex is what separates us from a biological perspective, while gender is more about what it means to be a particular sex.

Typically, clinical trials allow for a “self-reported” sociological gender. This is used for bed assignments and general grouping, but has little to do with the actual outcome of the clinical trial in most cases (unless an investigative compound causes a subject to exhibit behavioral traits of the opposite gender, which would certainly be a notable side effect).

Analyzing Sex and Gender Data in Clinical Trials

When it comes to analyzing data in clinical trials, it is more important to understand the clinical, chromosomal or biological sex of the subject.  This is critical when looking at lab results and comparing efficacy across groups. While this may seem like a straightforward situation, the collection of this information can be tricky.  Different standards organizations have gone about defining the collection of sex in different ways. Health Level  Seven (HL 7), a global authority on standards for interoperability of health information technology, has an Administrative Sex Value that offers six choices: Ambiguous, Female, Male, Unknown, Not Applicable, Other.

That’s a little more complicated than what we learned in middle school health class, isn’t it?

Determining gender gets even more complex. The HL7 comments concerning their Administrative Gender Code state that: Gender is a complex physiological, genetic, and sociological concept that requires multiple observations in order to be comprehensively described. Not exactly checking a box!

CDISC Definition of Sex in the Clinical Trial Process

The Center for Disease Control (CDC) offers nine choices for sex: Not Known, Male, Female, Not Specified, Unknown, Not Stated, Unsexable, Transsexual, Other. CDISC has adopted the National Cancer Institute’s definition - The assemblage of physical properties or qualities by which male is distinguished from female; the physical difference between male and female; the distinguishing peculiarity of male or female – and the following four options:

CDISC SynonymCdisc definition


A person who belongs to the sex that normally produces ova. The term is used to indicate biological sex distinctions, or cultural gender role distinctions, or both. (NCI)


A person who belongs to the sex that normally produces sperm. The term is used to indicate biological sex distinctions, cultural gender role distinctions, or both. (NCI)


Not known, not observed, not recorded, or refused. (NCI)


A person (one of unisexual specimens) who is born with genitalia and / or secondary sexual characteristics of indeterminate sex, or which combine fetures of both sexes (NCI)


That’s a little more clear. The reality is, in most cases we just identify sex as male or female. But with all these different options for identifying something as seemingly simple as sex, it makes it clear why it is so important to utilize top-notch eClinical products for electronic data capture and to ensure clean data in your clinical trials!

Do you have any thoughts on the gender and sex debate issue in clinical trials?  Please comment here.

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