Cancer deaths could be reduced by one third, or more, according to expert estimates. One of the strategies to reach this goal is the use of screening programmes. Women in most high-income countries will participate during their lifetime in a screening programme for cervical cancer, and another for breast cancer. Both types of screening have an essential component of image interpretation by a doctor – either a mammogram, i.e. a special x-ray picture of the breast, or a Pap smear, which is a sample of cells from the vagina that is examined under the microscope. These tests are like windows into the magnificent palace of the female body, through which doctors peer like nightwatchmen to try to make out whether any of the shadows in the darkness inside are dangerous lurkers.
Millions of such pictures are examined every year, by doctors suffering under the same unfavourable circumstances as pilots: everything is routine, but the consequences of even a slight error could lead to disaster and death. Decision-making is a challenge. Every doctor must calibrate him- or herself to a set-point where he detects as many as possible of the real positive cases without over diagnosing and creating false positives, which will cause patients to needlessly undergo maiming surgery. Doctors’ decisions, like anybody else’s, are affected by such mundane factors as their alertness, their mood, their serum caffeine levels, and the weather.
This subjectivity needs to be managed.
Of course, doctors have lots of strategies to do that. Most of the time, it works very well. Doctors meet, discuss cases in rounds, and recalibrate their set-points. The keep the images and monitor the patients for decades to see whether any tumours develop that they could have detected earlier. And they do research into the predictors of accurate diagnosis.
One such paper appeared last week in the American Journal of Roentgenology. It investigates the very plausible hypothesis that doctors who enjoy their work also diagnose more accurately. Berta Geller and her colleagues sent a questionnaire to 131 breast radiologists, and then linked their answers to known performance on 700 000 mammograms in a database. In the end, there was no significant connection between the reported enjoyment of interpreting mammograms and the performance of the doctors. This finding is very reassuring and in my opinion a bit surprising.
But these is more: The authors have investigated what factors are most likely to predict doctors’ enjoyment of interpreting mammograms, and these are the results:
The y axis shows the odds ratio, which can be understood as “fold change in likelihood”. As the diagram shows, doctors were roughly eight times more likely to enjoy interpreting mammograms if they are women! This was a much stronger predictor than the feeling of competence, which comes next. The most important negative predictor was the fear of malpractice suits. (This is a US study.) The “Non-salaried” bar in the middle compares doctors who are paid per case to those paid a fixed salary. Not much difference there.
Why on earth do women find the work so much more enjoyable? There were 101 men and 29 women among the doctors, which should be enough to keep random variation out of question. (That adds up to 130 doctors – one is missing, who perhaps did not state his/her gender.)
Are there hidden confounders? Perhaps the women were younger on average in this sample, and more enthusiastic? No, because older doctors enjoyed their job more than younger doctors did. Could it be that women feel disproportionately skilled at interpreting mammograms? Or is it in fact a real difference, due to some other factor such as that all the doctors identify more with female patients, or that women enjoy image interpretation more in general?
All rather unlikely explanations I think. But science is at its best when it reveals unlikely chains of causation to be true! I hope someone will make the effort to find out whether this is a consistent finding and, in that case, what causes it.
Full reference: B. M. Geller, E. J. A. Bowles, H. Y. Sohng, R. J. Brenner, D. L. Miglioretti, P. A. Carney, J. G. Elmore (2009). Radiologists’ Performance and Their Enjoyment of Interpreting Screening Mammograms American Journal of Roentgenology, 192 (2), 361-369 DOI: 10.2214/AJR.08.1647