Spanish to English Medical Medical (general)

This is from a medical study by Spanish researchers which compares different scales assessing recovery in stroke patients. It specifically concerns where different cut-off points are placed, which divide up the otherwise continuous numerical scales into sections such as "poor recovery", "moderate recovery" and "good recovery". Two of the scales seem to differ in their classification and the writer argues that this is due to the "nivel de exigencia" of the different scales, with one being less "demanding" than the other. So, some patients assessed as having a "good recovery" with the less demanding scale are classified as having a "moderate recovery" with the other scale. Another way of thinking about it would be that one scale seems to set the bar lower than the other, while bearing in mind that the scales actually take different kinds of data into account. Here's an example sentence: "Son escasas las investigaciones que han comparado el nivel de exigencia de las distintas escalas de valoración postictus".

There's the rub. Although "una exigencia" would be "a demand" in most contexts, "nivel de exigencia" would have to be something like "level of demandingness" which is obviously not appropriate. My current solution is "Few studies have compared how demanding the different post-stroke assessment scales are", but this paraphrase is awkward in some sentences. Other typical options for "exigencia" such as "requirement" or "strictness" don't really work here (I don't think). In the literature, many authors actually consider the problem from the opposite perspective, talking about how sensitive such scales can be, rather than how demanding they are (less demanding = more sensitive), e.g. http://stroke.ahajournals.org/content/33/8/2053.full

I'm considering using this option, but it means that a number of changes would have to be made to the text, which I would have liked to avoid. For example, it would mean inverting the way in which the author ranks the two scales in question in the conclusion ("La escala A es la más exigente, seguida de la B"). Also, "sensitive" has some positive connotations, which the writer of my text may not want. The frustrating thing is that "sensitive" has the right kind of adjective-noun pair, sensitive/sensitivity, seemingly lacking in the case of "demanding".

Another option might be to talk about "thresholds", but I'm sceptical as it is more or less synonymous with "cut-off point", which is used a number of times in the text, but the author chose not to frame the problem with this term.

Any ideas?

British English but all contributions welcome.