Internal quality control: best practice

Abstract

There is a wide variation in laboratory practice with regard to implementation and review of internal quality control (IQC). A poor approach can lead to a spectrum of scenarios from validation of incorrect patient results to over investigation of falsely rejected analytical runs. This article will provide a practical approach for the routine clinical biochemistry laboratory to introduce an efficient quality control system that will optimise error detection and reduce the rate of false rejection. Each stage of the IQC system is considered, from selection of IQC material to selection of IQC rules, and finally the appropriate action to follow when a rejection signal has been obtained. The main objective of IQC is to ensure day-to-day consistency of an analytical process and thus help to determine whether patient results are reliable enough to be released. The required quality and assay performance varies between analytes as does the definition of a clinically significant error. Unfortunately many laboratories currently decide what is clinically significant at the troubleshooting stage. Assay-specific IQC systems will reduce the number of inappropriate sample-run rejections compared with the blanket use of one IQC rule. In practice, only three or four different IQC rules are required for the whole of the routine biochemistry repertoire as assays are assigned into groups based on performance. The tools to categorise performance and assign IQC rules based on that performance are presented. Although significant investment of time and education is required prior to implementation, laboratories have shown that such systems achieve considerable reductions in cost and labour.

Setting up a service for a faecal immunochemical test for haemoglobin (FIT): a review of considerations, challenges and constraints

“…If introducing an IQC protocol, factors considered in a previous review in this journal should be taken into account 28. It has also been challenging for external quality assessment scheme (EQAS) organisers to develop meaningful EQAS to assess FIT analytical performance; EQAS that send out faecal like matrices spiked with Hb exhibit large variation in results from the participant laboratories, and it is difficult to ascertain whether these differences are preanalytical or analytical.…”

Quality control review: implementing a scientifically based quality control system

“…Finally, risk-based controls should be added to monitor specific failure modes of the particular test and test system. There are many other practical issues in routine SQC applications and operations, as discussed recently by Kinns et al 53 . These authors provide a lot of practical advice that is particularly oriented to NHS laboratories, including guidance for selection of SQC materials, assigning an SQC range, design of an SQC system on the basis of the observed Sigma-metric, frequency of SQC, use of patient data, practicality and cost of implementation, review of SQC data, and applications within a laboratory network.…”

No abdominal pain, no lipase

“…As this study showed, there are roughly as many appropriate requests not occurring as inappropriate requests occurring. Furthermore, assay quality will still need to be maintained with the demands for calibrations, Internal Quality Control and External Quality Assurance/Proficiency Testing analysis remaining typically the same. Unless reagent pack size can be reduced accordingly or the ‘on‐analyser’ lifespan increased, more reagents will be discarded if not used.…”