Potassium test handling improvements cut recollections to zero

(Aotea News, November 2010)

A project to improve the way we handle potassium tests has seen the number of blood recollections drop from 10 per week over the winter to zero.

Potassium testing, along with several other tests, can be affected by pre-test variables including phlebotomy technique, specimen storage, transport conditions and centrifugation delays. These pre-test variables can occasionally lead to compromised laboratory result.

For potassium testing, misleading results can also be caused by haemolysis during collection, delay in separation, refrigeration of unseparated blood, marked leucocytosis and thrombocytosis and limb muscle activity immediately before venepuncture. During the past winter, our monitoring picked up a rise in the normal rate of hyperkalemia. On average the laboratory needed up to two recollections per day of blood specimens for potassium tests — this was unusual.

Improvements put in place

After investigating pre-test processes, our laboratory made the following improvements:

• Timed tagging of specimens to ensure improved prioritisation of specimens according to their collection time. This is an advancement on our “first in — first out” rule to ensure oldest specimens are processed first, along with urgent specimens.
• Better insulation of specimen transport containers (keeping insulated container temperatures above 10ºC) following a datalogging review of specimen temperatures in transit to the laboratory.
• Centrifuging prior to transport to the testing laboratory for potassium specimens travelling longer distances.

We are pleased to report that since the introduction of these improvements there have been no recollections of blood specimens required for potassium tests.