Monday, February 23, 2015

Three things I learned about determining the cause of death

Last week I attended a lecture by forensic pathologist Professor Jo Duflou, Clinical Director of Forensic Medicine for the Sydney, NSW Forensic and Analytical Science Service. Forensics is a very sexy topic these days and when I said I was off to the talk, there was much forensics-envy. But those in the business agree its not quite as sexy in real life as it is on TV. They don't show good-looking actors buried under mounds of paperwork or caught up in decade-long inquests. Mind you its been a while since I've watched TV. I digress.

Professor Duflou, as a forensic pathologist, is charged with determining the cause of death and/or injuries, so he has spent his career largely in the post mortem room. He provided a fascinating insight into some of the challenges of pinpointing exactly how someone died.

For those who don’t know, an autopsy involves similar things to other medication investigations: taking a history, imaging, performing an external examination, then an internal examination, any additional special investigations (histopathology, toxicology, microbiology), and retention of organs. The forensic pathologist takes a methodical approach and progresses from a working diagnosis to the final diagnosis (although the final diagnosis may not be a definitive diagnosis).

When the rest of us recoil in horror when we read about a mass accident or multiple fatality in the paper, Professor Duflou and colleagues know there’s a high likelihood that the victims (deceased) will appear in their workplace.

In New South Wales, forensic pathologists investigate deaths under the Coroner’s Act (homicides, suicides, suspicious deaths, sudden unexpected deaths and so on) as well as non-coronial cases (consented autopsies under the Human Tissue Act). Coronial autopsies are ordered examinations determined to find out “what happened”, and collect evidence which may be used in legal proceedings. The number one reason for a coronial autopsy is sudden death where the cause is unknown.

These examinations can save lives. A lot of diseases that kill young people unexpectedly are familial, and other family members may need to be tested and treated for that potentially fatal condition.

Professor Duflou and colleagues are not fans of shows like “CSI”, which he calls “the worst forensic pathology example on earth”. Why? Because “all of their problem are always solved” (in an hour, no less).

So what did I learn?

  1. Microbiology doesn’t always provide answers. It makes sense. At the time of, and sometimes before death, our natural barriers to bacterial invasion (such as the skin) break down, allowing opportunistic microbes to jump on board. Unless death occurs in a freezer, putrefaction is inevitable. The blood stream is the main pathway of dissemination of microbes. There can also be a delay between onset of disease and death so that the infectious organism may have left the scene of crime before it can be detected. The classic example would be viral myocarditis. “The bug may have gone by the time you do the autopsy,” Professor Duflou said, “so you’re just stuck with inflammation.”
  2. The deceased have comorbidities. That may seem obvious, but think about it. Its human nature to seek a single cause of death. But during an autopsy, a forensic pathologist can end up with a list of conditions present, each one of which could have killed the victim. It can be impossible to determine with certainty which one caused death. And then there is the challenge of marginal pathology: “if there is a little bit of something, can it kill or not?”.  Most natural deaths are diagnosed by exclusion – as Professor Duflou said, “there are very few things that can kill you that can’t be anything else.” There are exceptions – a ruptured aorta or heart, a popped aneurysm. But for others it’s really hard to say it was definitely this infection or that lesion.
  3. Autopsies are a public health tool. Around ten per cent of people in New South Wales will have a coronial autopsy. Performing judicious microbiology on these cases could provide a lot of information that would be valuable for disease surveillance and so forth.

The talk was hosted by the Australian Society for Microbiology, which you can visit on Facebook join here