The previous entry dealt with some limitations of the ISO risk management standard for medical devices – ISO 14971. This entry covers one of the limitations in more detail.
ISO 14971 fails to embrace the error – detection – recovery scheme, since they omit recovery. To see the problem, consider a clinical laboratory example in which a serum sample is analyzed for potassium.
Error – As the specimen is processed, some error occurs (OK, I am not that good at making up errors), which hemolyzes the specimen. If the cause of the error is known, then steps might be taken to minimize or eliminate it.
Detection – A technician visually examines the specimen before it is analyzed. The hemolyzed specimen is detected.
Recovery – The technician does not analyze the specimen and notifies the appropriate party to get another specimen. The end result depends on the turn-around-time requirement after re-assay.
If the turn-around-time requirement is met, no effect of the original error is observed
If the turn-around-time requirement is not met, the effect of the original error is a delayed result.
In either of the above cases, the error – detection – recovery scheme has prevented an erroneous result as the effect of the original error. (OK, one could get an erroneous result in the new specimen).
Whereas recovery in this case seems trivial, what if just as the technician is ready to perform the recovery, he/she gets called away and never performs the recovery. There is a well known example of a failed recovery where the error was the incorrect leg was scheduled to be amputated – the error was detected – but the recovery failed. Although, the correct leg was identified in the operating room schedule (successful detection), there were multiple operating rooms and not all schedules were corrected (failed recovery) (1).
Where recovery becomes even more of an issue is when detection and recovery are located in different organizations. This is actually a common occurrence. For example, manufacturers detect a problem (this could be an official recall) and it is up to the hospital or clinical laboratory to follow the manufacturer’s recommendation as to the recovery (e.g., discard that lot of reagent).
In the risk management standard ISO 14971, a recommended control measure presents the opportunity for a failed recovery. ISO 14971 provides a hierarchy of risk control measures (mitigations), which in order of preference are:
1. Eliminate the error
2. Detect the error
3. Inform the user of the error possibility (e.g., state a limitation of the procedure)
Number 3 is really part of detection (e.g., the detection is communicated). Number 3 is also commonly used for interfering substances for in-vitro diagnostic assays. This error is the stepchild for diagnostic assays. For example, I once surveyed a year’s worth of Clinical Chemistry assay performance complaints and found that interferences were the main complaint (2). One can speculate how this happened. A clinician realized that some treatment or patient status was inconsistent with a laboratory result, the laboratory investigated, and the assay result was found to be incorrect with an interfering substance as the cause of the erroneous result.
So consider the risk control measure for an assay whereby the manufacturer lists 10 substances that may interfere with the assay. How can the clinical laboratory “recover” using this knowledge (e.g., detection)? They can’t. To determine the concentration level of ten substances in every specimen is impractical (too expensive). So to review this situation:
1. Eliminate the error – the manufacturer has tried, but failed. Ten substances still interfere (at or above certain concentrations)
2. Detect the error – the only “detection” possible is to inform the clinical laboratory. Note that all other common detection methods (external quality control, internal algorithms) fail.
3. Recovery – The clinical laboratory cannot perform a recovery
One should realize that whereas this is an undesirable state, it may be the best possible way of doings things given the economic constraints. As stated in the previous entry, the manufacturer is doing the right thing (as are regulators and the clinical laboratory).
However, the problem is that ISO 14971 would have us believe, that all risk is now at an acceptable level, which is not the case. The erroneous result is likely to occur, after which a cause is likely to be found since the manufacturer has stated a list of possible interfering substances.
Also, as in the previous entry, patient awareness is needed to be added to the mix as a significant way to prevent patient harm.
1. Scott D. Preventing medical mistakes. RN 2000;63:60-64.
2. Krouwer JS. Estimating Total Analytical Error and Its Sources: Techniques to Improve Method Evaluation. Arch Pathol Lab Med 1992;116:726-731.