Correlation of the first lateral flow-based Point of Care test to quantify infliximab and anti-infliximab antibodies in a finger prick sample with the reference ELISA technique

Background Current techniques to monitor clinical response may require several days and centralised facilities, which may cause delays in effective therapeutic decisions. Therefore, the use of a rapid decentralized test will facilitate patient management and improve patient care. Objectives The goal of this study was to validate the use of capillary blood in a real point-of-care (POC) setting for rheumatic patients under infliximab treatment by using Promonitor Quick lateral flow (LF) tests. Results were compared to the Promonitor ELISA reference technique in serum samples used by centralised laboratories. Methods A prospective, observational study was designed to evaluate the performance of a rapid LF test (Promonitor Quick IFX, Progenika, Spain). 160 infliximab treated rheumatology consecutive patients (400 samples) were recruited in two hospitals in Galicia, Spain. Prior to the infusion, a finger prick sample was obtained and analysed. Anti-infliximab antibodies were also determined with Promonitor Quick ANTI-IFX 1-4 . Results were read with the automated portable PQreader instrument. Additionally, a serum sample was collected for subsequent comparative analysis with either LF or ELISA tests. Qualitative (positive (PPA) and negative (NPA) agreements) and quantitative (Pearson correlation and bias) performance of the LF test was compared to ELISA, as well as between different specimens following CLSI EP09-A3. Results Overall agreement between Promonitor Quick IFX finger prick and ELISA test was 91% (88% PPA; 100% NPA). The quantitative comparison showed a good correlation (Pearson correlation coefficient: 0.85 and observed bias: 25%) (Table 1). Table 1. Performance results: infliximab drug Qualitative Comparison N* PPA NPA overall POC finger prick vs ELISA 274 88% 100% 91% POC serum vs ELISA 281 98% 100% 98% Quantitative Comparison N* Pearson correlation Bias POC finger prick vs ELISA 165 0.85 25% POC serum vs ELISA 181 0.91 6% *Only samples in the common measurement range for both methods considered. Performance results: anti-infliximab anti-drug antibodies Qualitative Comparison N* PPA NPA overall POC finger prick visual vs. PQreader 396 100% 99% 99% POC serum visual vs PQreader 398 100% 100% 100% POC finger prick PQreader vs ELISA 393 90% 99% 98% POC serum PQreader vs ELISA 395 89% 100% 99% Similar results were also observed when serum was used with either the LF or the ELISA tests (98% overall agreement, 0.91 correlation coefficient; 6% bias) (Table 1). Overall agreements for visual and automated (PQreader) interpretations with Promonitor Quick ANTI-IFX were 99% and 100% for finger prick and serum specimens, respectively (Table 1). Conclusion Promonitor Quick can be used to reliably quantify infliximab in capillary blood samples and results are comparable to those obtained with the reference ELISA technique. The use of the rapid POC test with finger prick will allow clinicians to monitor their patients in a fully decentralized mode to aid in the decision making process. PQreader is a sensitive portable equipment to report drug as well as antibody levels in the patient samples. References [1]Atreya, R. et al . J Crohns Colitis. 2019;13:S391 [2]Ametzazurra, A. et al . J Crohns Colitis. 2017;11:S335-S336 [3]Fiorino, G. et al . J Crohns Colitis. 2017;11:S388 [4]Facchin, A. et al . J Crohns Colitis. 2019;13:S349- S350 Disclosure of Interests M. Begoña Ruiz-Argüello Employee of: Employee of Progenika Biopharma - Grifols, Javier Pascual Employee of: Employee of Progenika Biopharma - Grifols, Lorena Del Rio Employee of: Employee of Progenika Biopharma - Grifols, Ane Urigoitia Employee of: Employee of Progenika Biopharma - Grifols, Cristina Balo-Farto: None declared, Carlos Fernández-López: None declared, ANTONIO MERA VARELA: None declared, Francisco Javier de-Toro-Santos: None declared, Daniel Nagore Employee of: Employee of Progenika Biopharma - Grifols, Amagoia Ametzazurra Employee of: Employee of Progenika Biopharma - Grifols