Repeat patient Testing‐Quality control: An example of implementation in a network of commercial laboratories

The theory and calculations underpinning Repeat Patient Testing‐Quality Control (RPT‐QC) have been presented in prior publications. This paper gives an example of the process used for implementing RPT‐QC in a network of veterinary commercial reference laboratories and the stages associated with the transition to the sole use of RPT‐QC. To employ RPT‐QC in this commercial laboratory network, eight stages of implementation were identified: (1) education, (2) data collection, (3) calculations, (4) QC recording and documentation, (5) running RPT‐QC in parallel with a commercially available quality control material (QCM), (6) development of a Standard Operating Procedure (SOP), (7) development of complementary aspects supporting RPT‐QC, and (8) sole use of RPT‐QC. Advantages of RPT‐QC included cost savings for QCM and External Quality Assessment (EQA) participation and the ability to use commutable specimens with a veterinary matrix at a result level that is of clinical significance for the species. A disadvantage of RPT‐QC using a single level of control was the inability to demonstrate stable performance over a range of results. Future avenues for investigation include ongoing refinement of control limits using a pooled standard deviation of the duplicates (SDdup), Sdup over time, investigation of blood samples from species other than the dog, and manipulation of specimens to produce “low abnormal” or “high abnormal” RPT‐QC specimens.