Humans cannot perform tasks correctly each time. Unaided, 98
percent correct performance is excellent. Nevertheless, when the
consequences of error are severe, multiple system redesign steps
may be needed to reduce the rate to an acceptable level.
Achieving zero error may be impossible. Transfusion medicine
provides a good example of the roadblocks to perfection.
Hospitals have taken vigorous steps to reduce the risk of major
hemolytic transfusion reactions resulting from an incorrect
crossmatch. In a recent paper (Ansari and Szallasi), the authors
look at their success at eliminating discrepancies between the
patient identified on the tube’s label and the patient whose
blood is in the tube (wrong blood in tube — WBIT).
In large-scale studies, the detected WBIT rate tends to be about
0.04 percent, but the real WBIT rate is even higher. Detection of
the error only occurs when some red flag arises, such as a
mismatch with an earlier recorded blood type, realization by the
phlebotomist that he made a patient recognition error or
post-facto analysis of an unexpected transfusion reaction.
The authors noted that their rate was similar to the typical
rate, and WBITs persisted even when policies were changed to have
two witnesses to patient ID and bedside tube labeling. They then
added a second control, the two-tube/check-type method. This
requires two different persons to draw blood from the same
patient at two different times for patients who had no
previously-recorded blood type. This relatively simple step
provides a “defense in depth,” adding a second, independent type
check, markedly reducing the risk of WBIT.
With the two-tube/check-type method, a WBIT event will be caught
when the ABO or Rh blood types are discrepant. However, WBIT may
still occur when the two samples come from patients with the same
major blood type (e.g., A+.) Then the crossmatch, which also
screens for rarer incompatibilities, may still be in error.
Indeed, the authors detected several potential errors by other
means that were not detected by the two-tube/check-type method.
Further rate reductions may require more automation and
innovations in patient and blood sample identification. To quote
Richard Friedberg of Baystate Health System: “Absent a bar-code
on the patient’s forehead, the rest are all compromises.”
Ansari S, Szallasi A. “Wrong blood in tube”: solutions for a
persistent problem. Vox sanguinis. 2011;100(3):298-302.