More on Antwerp, EFLM and pre-analytical error


One of the talks in the Antwerp conference referred to an EFLM working group to come up with performance specifications for pre-analytical error. There is a talk on the EFLM website about this.

The recognition that pre-analytical error is a big part of ensuring the quality of laboratory tests is of course important; however, it’s hard to see how separate performance specifications for pre-analytical error (e.g., separate from analytical error) can be useful. [Actually, the presenter from the Antwerp conference agreed with my skepticism during a break.]

Pre-analytical error can be classified into three types

Type 1 – An error that is completely independent of the analytical process. Example: failure to wash the site that is sampled for a glucose meter test. If the site is contaminated with glucose, any glucose meter will report an elevated (and erroneous) result.

Type 2 – An error that is partly dependent on the analytical process. Example: a short sample for a glucose meter test that has an algorithm in the meter to detect short samples. If the algorithm is defective (an analytical error) and there is a short sample (a pre-analytical error), the glucose result may be erroneous.

Type 3 – A pre-analytical error that is indistinguishable from the analytical process. Example: air bubbles in a pO2 blood gas syringe. No matter who is performing the test, there is the possibility of having bubbles in the sample, a pre-analytical error which can cause an erroneous result.


One of the problems is that a typical evaluation will attempt to meet (analytical) performance specifications with type 1 and type 2 errors excluded from the evaluation. This is of course recognized by this EFLM group, hence their task. I note in passing that when type 3 errors occur, the performance evaluations include such pre-analytical errors even when trying not to (by excluding the possibility of type 1 and type 2 errors).

One fear is that the EFLM group will come up a bunch of separate performance specifications for pre-analytical error, independent of specifications for analytical error. I don’t see how this can work.

What would I do? I would use a reliability growth metric, which counts all errors (regardless of source) – see this paper.

Finally, where I wrote pre-analytical error, it should be pre- and post-analytical error.

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