μGnostics 101

μGnostics: the contribution microbiology makes to Diagnosis

The dust is settling after a busy weekend on call, dealing out decisions on a variety of infectious diseases. So much weight is placed on the results of lab tests, yet all too often they only form a part of a much bigger diagnostic picture. Knowledge of how microbes behave during the course of infection, and how they play their part in the process is not the same as the diagnosis. In fact, the personal responsible for the diagnosis is not usually the same as the person driving back office functions such as the clinical lab.

If you drill down into the etymology of diagnosis, it becomes clear that this is a process linked to a special kind of knowledge, recognised in the specifics of the relationship a physician has with their patient. To speak of a ‘laboratory diagnosis’ is to truncate a complex process that begins and ends with a poorly patient. It would be more correct to see the clinical laboratory as a toolbox full of clinical decision support gear.

Thinking aloud, this begins to explain the difficulty we have with the unrealistic expectations generated by terms like ‘diagnostic tests’. Neither the tests nor the tester make a diagnosis. They may, however, support a diagnosis or another critical decision process.

ætiology; a core issue for μGnostics

First generation μGnomes realised that they needed a method to establish a causal relationship between a microorganism and an infectious disease. They came up with a short list of rules against which any such linkage could be judged. The most famous of these is often known as Koch’s Postulates. Since then a series of improvements have been proposed, most recently including our own (see tag below). The full set of rules has only rarely been applied to support a specific microbe-disease pairing. Nevertheless, a short form of this method has been used to identify the likely cause of infection in day-to-day clinical practice, combining Koch’s Postulates with Occam’s razor, where the fewest types of microbe that explain the entire disease process are used to determine what course of action should then be taken.

The cartoon version of this managed process is One bug-One disease-One drug. Of course, that is a gross oversimplification. The devil, as they say, is in the details and must have a particularly wicked sense of humour.

So that brings us back to μGnostics. The root cause we so often look for, using a short form of the Priobe Argument, is what we then use to guide our choice of treatments, and on a larger scale, our preventive measures. These are the things that occupy most of my waking hours, and some of my dreams as well.

μGnome.

Comments

  1. Hi, very interesting post, greetings from Greece!

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