Does the gender of your vet influence your TB test result?

I thought I'd repost this given that the paper in question has been accepted for publication subject to some minor corrections.

According to the analysis, a vet's gender is related to the outcomes of TB tests. Its rather strange - I mean why would it? But curiously these kinds of results are no different to other findings elsewhere in human medicine: female doctors do things that male doctors dont. Im not into biological determinism, so Im uneasy with the idea that somehow there are inherent qualities that men or women have - I would have thought that there were wider contextual factors that were influencing the results of tests rather than gender itself.

The analysis is based on bTB test results between 2004-2009 in three different counties  of England and Wales - all high incidence areas. The results appear to show that even when controlling for herd size and test type, there are substantial differences between male and female vets in terms of the number of reactors they find.

Who finds the most reactors you say? Most people are surprised when I tell them - male vets. But finding the most doesnt necessarily mean they are better. The difference could be down to a range of factors such as biases in the way tests are distributed and/or differences in interpretating what is best for borderline cases. Either way, what the results show is that it is not a good idea to compare the performance of vets using these figures - and that issues affecting performance may instead lie in the way veterinary regulation is organised.

These results emerged partly by accident. I was looking at the data for other reasons and thought it would be interesting to examine. Gender is the only "social" variable in the VETNET database which is a shame. Due to anonymity reasons I can't include age, which would be interesting, or length of service (although I might be able to work out some proxies for this). I might be able to include some other factors such as the number of unique clients, or repeat visits in future analyses, but the way the data is organised in VETNET will make this a bit tricky.

The most disappointing thing is that originally I wanted to do a comparison of practices over time but this turned out to be impossible. This is because when you extract data from VETNET, the practice name for each vet is the current one. So, if a vet had moved between say 4 practices over 4 years, the data for that time period would not reveal that. Luckily, with the help of some local knowledge from a friendly vet, we spotted it - a practice that didnt exist 5 years ago was coming up in the results before it was established. I wonder how many people know that - I dont think the managers of the database knew until I pointed it out. And sadly that means its impossible to look at differences between practices, how they have changed over time, or the careers/migration patterns of vets using this database too. Maybe the new SAM system will sort all that out...