Reduced bracketed control concept for automated biochemistry analyzers: A reliable and cost-effective setup

Abstract

Objectives

Today, most biochemical analytes are produced on automated analysers in continuous mode, and internal quality control (IQC) protocols often include a “critical control” analysed after maintenance and a “bracketed control” (BC) analysed periodically along with patient samples. As quality control materials and reagents are costly, the BC might be reduced to one level of IQC and include only selected analytes, covering testing principles and essential technical parts of the analyser. This study aimed to investigate whether such a reduced BC (rBC) is reliable for detecting clinically relevant analytical problems.

Methods

Over 8 months, we compared an rBC with nine analytes and one IQC level with a full BC (fBC) with 65 analytes and two IQC levels regarding the analytical problems revealed.

Results

A total of 1,463,512 patient results were produced. With the fBC and rBC, respectively, 1669 and 996 patient samples were reanalysed due to an IQC result outside acceptance limits, resulting in the correction of 311 and 222 patient results. The rBC overlooked 89 (0.061 ‰) patient results outside our correction limits, only two of which were judged to be of potentially serious clinical importance. The extra annual cost of identifying these errors in our setting is approximately 220,000 €.

Conclusions

In our setup, the rBC overlooked only very few errors of clinical importance. This rate might be further reduced by including in the rBC any critical tests that are not prone to patient-based real-time quality control, which should be used for remaining, relevant tests.