Chapter 4: Detection Bias

The idea of detection bias is one that many people are oblivious to, as there is so much faith in doctors and the health system generally.  However, the truth of the matter is doctors do not know everything, and, as I have explained already, there is a definite health establishment that has great power.  Furthermore, the notion that smoking is incredibly harmful and most smokers will die of lung cancer is so prominent and engrained within us and our health practitioners that the simple truth is lung cancer is often overlooked in non-smokers simply because doctors are not expecting it to be there, and thus do not bother looking.  This is detection bias.   

The phrase there are lies, damn lies, and then there are statistics probably has no greater relevance than in the field of smoking, and there is no doubt that detection bias leads to misleading and untrue statistics that only worsen the belief that smoking causes such harm, and this in turn simply increases the chances of detection bias.  Clearly, it is a vicious cycle.

Of course, many people will deny detection bias exists and claim doctors know what they are doing and this is simply an excuse used by smokers to defend their habit.  A logical response, but it has one problem: there is scientific evidence proving detection bias exists, and exists to a degree that it causes misleading statistics.  

In 1959 a study was conducted by Heasman and Lipworth [1] in which they surveyed reports from 75 National Health Service hospitals (the NHS being the primary care system in Britain, providing free health care and funded by taxpayers money.  The alternative is private healthcare, whereby people pay extra money for healthcare).  In these 75 hospitals, physicians diagnosed 338 cases of lung cancer, yet pathologists doing autopsies discovered 417 cases.

[1] Heasman, M.A., and Lipworth, L. (1966) Accuracy of Certification of Cause of Death, Studies on Medical and Population Subjects

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