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La Rivista Italiana della Medicina di Laboratorio 2020 Giugno;16(2):114-8

DOI: 10.23736/S1825-859X.20.00066-3


language: Italian

Analytical interferences on hs-cTnI: specimen re-centrifugation

Giulio MARINO 1, 2 , Jessica VIOLA 3, Maria A. BURGIO 4, Vincenzo ROCCAFORTE 2, 5, Piero CAPPELLETTI 6,, a nome del Gruppo di Studio sui Marcatori Miocardici (GdS MM) della Società Italiana di Patologia Clinica e Medicina di Laboratorio (SIPMeL)

1 Laboratorio Analisi, Ospedale di Vergato AUSL Bologna, Vergato, Bologna, Italia; 2 Patologia Clinica e Biochimica Clinica, Università degli Studi di Milano, Milano, Italia; 3 U.O.C. Patologia Clinica, P.O. Umberto I, ASP 4 Enna, Enna, Italia; 4 Patologia Clinica Ospedale Barone Lombardo, Canicattì-ASP Agrigento, Canicattì, Agrigento, Italia; 5 Dipartimento di Medicina di Laboratorio, Area di Analisi Chimico Cliniche, ASST Grande Ospedale Metropolitano Niguarda, Milano, Italia; 6 SIPMeL, Catelfranco Veneto, Treviso, Italia

BACKGROUND: Preanalytical phase is the step of the laboratory diagnostic process (brain to brain loop) with higher error rate and centrifugation of the sample represents a critical point as it can generate artifacts that will interfere with the entire analytical process and with the interpretation of results. The aim of this work was to evaluate the possible effects of re-centrifugation of the sample in cardiac troponin determination (cTnI) in the presence of not clinically consistent values.
METHODS: Serum concentrations of cardiac troponin I (cTnI) were compared in 40 patients before and after re-centrifugation. Blood samples, collected into 4.5 mL vacuum lithium heparin gel tubes (BD Vacutainer®, LH PST™ II, ref. 367376), were centrifuged at 2000 g for 10 min as soon as they arrived at the laboratory and then immediately analyzed. The same samples were centrifuged a second time at 2000 g for 10 min and analyzed again. We used a Heraeus® Multifuge® 3s centrifuge, with BIOShield™ 4 x 250 mL Swinging-Bucket Rotor, braking and acceleration profile set on maximum (85/70s). cTnI concentration was measured using the two-step highly sensitive sequential immunometric assay (sandwich); the 600 DXI Access (Beckman Coulter, Milan, Italy) chemiluminescent automated analyzer was used (CLIA). Statistical analysis was performed by MetComp Software ver.1.0.
RESULTS: A median hs-cTnI value of 15.45 ng/L (interquartile range, IQR, 6.2÷41.55) was obtained by single centrifugation (SC) and of 14.75 ng/L (IQR 5.175÷41.375) after re- centrifugation (RC). The SC-RC bias was 1,005 (95% CI: -1.155÷3.165) ng/L, the percent bias 4.008% (95% CI: 1.587÷6.428) with a Pearson’s correlation coefficient =0.999 (P≥0.05). The Passing-Bablok regression equation was y=-0.1162 (95% CI: -0.3097÷0.0730) + 0.9835 (95% CI: 0.9680÷0.9957) x.
CONCLUSIONS: Our data show that cTnI concentrations are not subject to statistical significant changes after a second centrifugation compared to a single centrifugation. The bias between the two series of measurements 4.008% (95% CI: 1.587÷6.428) is consistent with the CV% of the analytical method used (~4% estimated at the median concentration of our samples) and would not influence diagnostic and therapeutic decisions. This result differs from other similar studies using the previous generation assays for cTnI measurement that showed a significant reduction in the value of cTnI concentration after re-centrifugation. The hs-cTnI assay, among other benefits, avoids the preanalytical interference derived from repeated centrifugation, that is an effective way to sort out “false positive” results due to the presence of fibrin in the sample.

KEY WORDS: Pre-analytical phase; Centrifugation; Clinical laboratory techniques

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