NOVELLO E., MION M.M., ZANINOTTO M., PLEBANI M.

1. AQT 90 FLEX Dimension RxL AQT 90 FLEX Dimension RxL PERFORMANCE EVALUATION OF THE NEW POINT-OF-CARE TESTING FOR CARDIAC TROPONIN I WITH THE RADIOMETER AQT90 FLEX ANALYZER NOVELLO E., MION M.M., ZANINOTTO M., PLEBANI M. Department of Laboratory Medicine, University-Hospital, Padova (Italy). Measurement of troponins plays a key role in the diagnosis of myocardial infarction and current guidelines (ESC/ACC) require that a tuornaround time (TAT) of 1 hour or less should be achieved for cardiac marker assay. On the other hand, the reorganization of Laboratory Medicine services in areas sometimes far awayfrom Clinical Hospital, make these guidelines more difficult to support. The rationale for Point-Of-Care testing (POCT) Technology depends on the need and the ability to achieve a rapid TAT for decision making in the diagnosis of suspected Acute Coronary Syndrome. POCT can’t replace Laboratory tests, but must be accurate and equivalent to Laboratory based diagnosis. POCT has a definite setting in managment: when very short TAT is required, such as the Emergency Department, or whereas Laboratory Services are distant from Clinical Hospital. AIM OF THE STUDY was to evaluate analytical performances of the new POCT AQT90 FLEX analyzer (Radiometer Medical ApS Denmark) for cardiac troponin I (cTnI) determination. INTRODUCTION AQT90 FLEX isa fully automatic continuos-access analyzer, with a throughput up to 30 tests per hour. The analyzer performs sampling from a manually loaded capped primary sample tube, after which the automatic processing takes place; the measurement principle is a sandwich immunoassaybased on universal all-in-one dry-reagent concept: the sample and the assay buffer are automatically added to the cup containing the assay-specific agents. The signal from the tracer antibody labeled with europium is measured by means of time-resolved fluorometry. Time to first result for cTnI is approximatively 18 minutes. cTnI values are expressed in µg/L. For the IMPRECISION STUDY, 9 plasma pools (PPs) (K2-EDTA) were tested for the intra-assay (n=10 for each PP) and beetween days (n=80 for each PP) imprecision respectively, according to CLSI (NCCLS) EP5-A protocol (Figure 1). For COMPARISON STUDY,108 matched whole blood (K2EDTA) and plasma (Lithium-heparin) samples were tested using the AQT90 FLEX and the RxLDimension (Siemens Healthcare Diagnostic, USA), the analyzer used in our laboratory for the routine assays of cardiac markers (Figure 2 a,b). AQT90 FLEX cTnI concentrations were obtained at first, using a standard haematocrit proposed by manufacturer and subsequently, introducing a real hematocrit value obtained from routine analyzer (Sysmex XE-2100,Kobe, Japan). (Figure 3 a,b) MATERIALS AND METHODS RESULTS Figure 1. Imprecision study Plasma pools concentrations for the between-day imprecision: 0.017-0.084 µg/L Corresponding CV range : 4.80-13.72% Plasma pools concentrations for the intra-assay imprecision: 0.022-0.046 µg/L Corresponding CV range : 5.75-10.99% 10% CV=0.023 µg/L. Figure 2 (a,b). AQT90 FLEX versus Dimension RxL Data from AQT90 FLEX were obtained using measured haematocrit cTnI concentration range: <0.010-25.00 µg/L. Applied cut-off: 0.023 µg/L (AQT90 FLEX), 0.15 µg/L Dimension RxL). Linear regression analysis: AQT90 FLEX= 0.2057 X Dimension RxL +0.0025 (r=0.99) (a); Observed agreement: 98%(b) Positive cTnI N=81 Negative cTnI N=27 a) Positive cTnI N=81 80 1 Negative cTnI N=27 1 26 b) • Figure 3 (a,b). Hematocrit values in the population studied • Measured hematocrit range: 22.6 - 48.7%. • When comparing the AQT90 FLEX cTnI results obtained using the measured hematocrit and the standard hematocrit(42%), no differences in sample classification were evidenced. Standard hematocrit(42%) a) Positive cTnI N=82 Negative cTnI N=26 Positive cTnI N=81 81 0 Negative cTnI N=27 1 26 b) The cTnI measurement evaluated is a simple to use, rapid (time to first results: 18 min, continous samples loading) and safe POCT assay, showing satisfactory analytical performances. The technology is suitable for the measurements of cardiac troponin by unskilled personnel in critical settings such as in emergency department and cardiac care unit. DISCUSSION AND CONCLUSIONS