Adverse event causes and errors

In one of the blogs I scan, I came across an entry that merits comment. Dr. Wachter refers to a recent article which has been in the news which suggests that medical errors are more common (10 times perhaps) than suspected.

In the entry, Dr. Wachter goes on to give a hypothetical example about a patient taking Coumadin who has a GI bleed while her INR was in the therapeutic range. The example is a little fuzzy so I’ll change it to say that her INR was actually 3.5 (aiming for 2-3) and the high INR was found out after the bleed event.

I have trouble with Dr. Wachter’s sentence – “If her INR had been above the therapeutic range (say, 3.5, when we’re aiming for 2-3) but there was no overt error identified (she was on a reasonable dose, being monitored at the correct intervals), we’d call that preventable harm (you wouldn’t have to think too hard to envision a system that might have caught and fixed this problem before the bleed), but not an error.”

This says that if one does not identify an error, there was no error!

All adverse events have causes – the something that produced the adverse result. An error is performing a procedure incorrectly – a mistake. Errors can be far removed from the adverse event, can exist but are not detected, and in some cases, the adverse event cause does not have an error.

Here are two of many possibilities, using the clinical laboratory since an INR was involved.

Case 1 – Patient sample mix up, identified and reported by the laboratory, after the adverse event.
Case 2 – False negative QC event identified and reported by the laboratory, after the adverse event.

In case 1, the laboratory made an error and caused the adverse event.

In case 2, a bad reagent caused the adverse event, but the laboratory did not make any errors. They were correctly following procedure. That is, a QC result has imprecision and the QC process in place (e.g., QC rules) has certain (low) probabilities of false positives and false negatives. Thus, QC could indicate results are acceptable, when they are not.

Another viewpoint of case 2 is that the adverse event was caused by the socioeconomic practice of medicine. The laboratory followed regulatory accepted ways of controlling quality. These practices are a tradeoff between effectiveness and cost.

The problem with Dr. Wachter’s suggestion is that it provides an incentive to not look very hard for errors. Thus, if in case 1, no one found out about the patient sample mix up, according to Dr. Wachter, there would have been no error.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: