Abstract:
BACKGROUND : Accurate potassium measurements are necessary for effective clinical
management of hyperkalaemia. Pre-analytical factors may affect laboratory measurements,
leading to erroneous results and inappropriate patient management and negatively impact the
efficiency and finances of laboratories and hospitals.
OBJECTIVE : This study evaluated the impact of rejected potassium test requests on laboratory
service.
METHODS : We conducted a retrospective descriptive study to assess potassium test data at a
public laboratory in Pretoria, Gauteng, South Africa, using samples collected from an academic
hospital, peripheral hospitals, and outpatient clinics between January 2018 to December 2018.
We assessed the relationship between reasons for rejection and health facility type, as well as
financial implications for the laboratory.
RESULTS : The potassium result rejection rate was 15.1% (29 806 samples), out of the 197 405 requests
received. The most common reasons for rejection were old sample (> 1 day old) (41.4%; 12 348
rejections) and haemolysis (38.2%; 11 398 rejections). The most frequent reason for rejections at the
central, academic hospital was haemolysis (42.0%), while old sample was the most common reason
for rejection at peripheral hospitals (43.4%; 4119/9493 requests) and outpatient health facilities
(57.2%; 7208/12 605 requests) (p = 0.022). The total cost of potassium sample rejection over the
study period was substantial, given the resource constraints in this setting.
CONCLUSION : Peripheral hospitals and outpatient departments accounted for the majority of
rejected potassium testing results, possibly resulting from delays in transportation; causing
substantial financial impact on the laboratory. Improved sample collection, handling, and
expedited transportation are recommended.
WHAT THIS STUDY ADDS : This study highlights the importance of appropriate sample collection
and handling and the undesirable consequences of non-adherence to these pre-analytical
considerations.
