Wednesday, December 18, 2013

Why Is Merging Test Catalogs So Hard?

It is FAQ Wednesday, when I take a FAQ off the pile and address it.

Today's frequently asked question is "why is merging test catalogs so hard?"

This question fits O'Flaherty's first law of applied technology: "It is usually not the technology that takes the time."

This question arises in a number of contexts:
  • Lab Manuals across organization (eg hospital systems)
  • Lab Manuals across labs (eg main lab and satellite lab)
  • Ref lab interfaces (order from one catalog, process from another)
  • Historical data archives (showing results from a previous catalog)
The answer is always the same: assumptions and comparisons.

When considering a lab result, there is a huge amount of assumed context:
  1. the collection method sometimes matters, sometimes does not;
  2. the methodology sometimes matters, sometimes does not;
  3. the actual value sometimes matters, sometime only the High / Normal / Low flag;
  4. having a basis of comparison to prior results sometimes matters and sometimes does not
Take Vitamin D levels for example: there are a couple of ways to measure it (methodology) which vary in exactly what they measure and how accurately they measure it. If you are a specialist, these differences may be very important. If you are a generalist, these differences may be meaningless to you. If you are trying to provide historical context by evaluating a series of these results, you almost certainly assume that the methodology was constant, which ever methodology was used.

The problem arises when catalog A only has "Vitamin D" and catolog B has "Vitamin D (the cool one)" and "Vitamin D (the usual one)". How do work across the catalogs?

There is always renaming to enforce consistency, but that is not straightforward and it is often politically charged: someone wins and someone loses. Furthermore, changing the name of a test is problematic: should the clinician infer that the assay has changed somehow? If so, how?

There is add new tests to enforce consistency, but is also a qualified success: what if the new test is essentially the same as the old one? How does the clinician know that, how does the software which displays the results know that these two "different" tests are the same lab assay?

Worse, making these decisions requires many different skill sets: clinical, lab and data modelling. So why is merging test catalogs so hard: because there is so much to it and so much of it is not immediately apparent. Hello, Titantic, meet Ice Berg.

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