Evaluation of the performance of a quantitative point-of-care CRP test
Authors: Ellis JE , MacLuskie S , Craig D , Lehane L , McInnes G , Harnett J , Cameron G , Moss P , Gray A 
Published: May 2022

Introduction

C-reactive protein (CRP) is an established acute-phase marker for infection and inflammation, which can help guide clinical decision-making in primary and secondary care. Many European guidelines recommend point-of-care (POC) CRP testing to improve antimicrobial stewardship in primary care. This performance evaluation study assessed the equivalence of the quantitative POC LumiraDx CRP Test compared to a laboratory-based reference method.

Methods

Method comparison, matrix equivalency, and precision were evaluated. Plasma samples from secondary care patients presenting with symptoms of infection or inflammation were analyzed centrally using the LumiraDx CRP Test and the reference test (Siemens CRP Extended Range for Dimension® Clinical Chemistry System). The method comparison was conducted used Passing-Bablok regression analysis with prespecified criteria of r≥95 and a slope of 0.95–1.05. The REACT study (NCT05180110) evaluated the equivalence and precision of the testing modalities (fingerstick, venous blood, and plasma samples from the same secondary care patient) using Passing-Bablok regression analysis of the results of the POC LumiraDx CRP Test.

Results

In analysis of 320 plasma samples from 110 patients, the POC LumiraDx CRP Test demonstrated close agreement with the reference method, meeting the prespecified performance criteria (r=0.99, slope of 1.05, N=110). Paired replicate precision of the testing modalities was high, with mean %CV of 6.4 (plasma), 6.6 (capillary direct), and 8.1 (venous blood). Passing-Bablok regression showed matrix equivalency for all replicate pairs of the testing modalities, with r values across all sample types of 0.97–0.98.

Conclusion

The quantitative POC LumiraDx CRP Test showed very close agreement with the established laboratory-based test when using capillary blood, venous blood, or plasma. The use of capillary blood testing in particular is beneficial in both primary and secondary care, with this portable test system providing rapid quantitative results within 4 minutes, potentiating the ability to help guide clinical decision-making.

Data from two study collections, the NOVEL study and the REACT study with a trial registration: ClinicalTrials.gov identifier, NCT05180110, were used in this performance evaluation.

Key summary points

C-reactive protein (CRP) measurements are clinical markers for infection and inflammation, commonly used in primary and secondary care

Point-of-care (POC) CRP testing can assist primary care clinicians in making an immediate decision as to whether to prescribe antibiotics while the patient is still at the clinic

POC CRP testing that provides quantitative results near to the patient can be useful in emergency care assessment of patients and in hospital monitoring of antibiotic therapy

The POC LumiraDx CRP Test has demonstrated quantitative results comparable to those obtained using a recognized laboratory system using plasma

The POC LumiraDx CRP Test has also demonstrated matrix equivalence of capillary blood (both direct application and transfer tube), venous blood, and plasma