A Rapid Chemiluminescent Substrate to Improve Signal-to-Noise Performance and Reduce Endogenous ALP Background




Beckman Coulter is developing a new immunoassay system that will run current Access immunoassays as well as an additional new menu. Goals for this new system include improved turnaround times for all assays, thereby meeting STAT test requirements while improving overall platform throughput. A key component of the new system is a new chemiluminescent substrate, Lumi-Phos PRO (formerly LumiFAST), employed to generate the light signal response. This new substrate is composed of a buffered surfactant enhancer system supporting an ALP-sensitive acridan. When the acridan is triggered in situ, it forms a dioxetanone, which immediately decomposes and emits light.


Luminometer read time was assessed by determining the change in relative light unit (RLU) signal over 32 to 72 seconds using an ALP-based enzyme test method and several commercialized Access immunoassays. Improved signal-to-noise performance was demonstrated by comparing calibration curves from several sensitive immunoassays generated using Lumi-Phos 530 with curves generated with Lumi-Phos PRO. The impact of interference from endogenous ALP was determined by assessing a panel of patient samples previously identified to contain these interferents using assays tested with both substrates.


Luminometer read time is approximately 5 minutes shorter for Lumi-Phos PRO than for Lumi-Phos 530. Three- to six-fold increases in signal-to-noise performance were demonstrated across the assays. Samples with known endogenous ALP interferents displayed greater than 50% reduction in spurious elevations when using Lumi-Phos PRO as compared with the values observed with the same samples using Lumi-Phos 530.


The new substrate has been optimized to rapidly generate signal, improve signal-to-noise performance, and reduce interference from endogenous alkaline phosphatase (ALP) in comparison to Lumi-Phos 530. This new substrate presents the opportunity to significantly shorten the time to first result while simultaneously improving assay sensitivity.

At a Glance


Minutes shorter luminometer read time – down from ~6.3 minutes to 1 minute

Up to 6

Fold median increase in signal-to-noise performance with >50% reduction in spurious elevations

73 %

Reduction in false reactives with high endogenous alkaline phosphatase levels


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Learn more about Lumi-Phos PRO and other innovations on the Beckman Coulter DxI 9000 Access Immunoassay Analyzer