Evaluation of the Cardiac reader^® as a point-of-care instrument for measurement of fibrin D-dimers in dogs

Summary

Objective: The aim of this study was the evaluationof the automated point-of-care analyzer Cardiac reader^® for quantitative fibrin D-dimer measurement compared to the Liatest™ D-Di™ run on the bench top analyzer STA Compact (all Roche). Material and methods: 41 fresh canine blood specimens submitted from the Clinic for Small Animals, Justus-Liebig-University Giessen were included. Measurement of fibrin D-dimers with the Liatest™ D-Di™ immunoturbidimetric assay was performed in citrated blood plasma stored at –80 °C until analysis. Using the Cardiac reader, D-dimer plasma concentrations were measured with an immunological assay in heparinized fresh (< 1 hour) whole blood specimens. Results: Mean intra-assay coefficient of variation (CV) was 6.13% (range: 2.2–10.0%) for the Liatest™ D-Di and 19.8% (range: 20.1–19.6%) for the Cardiac reader. Fibrin D-dimers detected with the STA Compact exceeded the upper limit of the reference interval (0.4 μg/ml; n = 62 healthy dogs) in 20/41 samples. There was a fair correlation between D-dimer measurements with the Cardiac reader and the comparison method (r = 0.78). Generally, results were underestimated with a mean proportional bias (0.45 μg/ml). The area under the Receiver Operating Characteristic (ROC) curve was 0.895 regarding the detection of increased fibrin D-dimers with the Cardiac reader. At a cut-off value of > 0.2 μg/ml, sensitivity/specificity were 85%/91% and positive/negative likelihood ratios were 8.93/0.17. At a lower cut-off value of 0.15 μg/ml sensitivity and specificity were 90% and 66%, respectively. Conclusion and clinical relevance: The Cardiac reader can be used for quantitative measurement of canine D-dimers, however, due to the odds of false negative results and the high imprecision the comparison method should be preferred.

Zusammenfassung

Ziel dieser Studie war die Evaluation des automatischen Notfallanalyse-Geräts Cardiac reader^® für die quantitative Messung von FibrinD-Dimeren mit dem immunologischen Test Cardiac D-Dimer™. Als Vergleichsmethode diente der mit dem Großgerät STA Compact durchgeführte immunoturbidimetrische Liatest D-Di™ (alle Roche Diagnostics GmbH). Material und Methoden: Untersucht wurden 41 frische kanine Zitratblutproben. Sie stammten von Hunden mit Verdacht auf Verbrauchskoagulopathie, hämorrhagischer Diathese, Thrombosen, Leberinsuffizienz, Hyperkalzämie, Neoplasien sowie von zwei gesunden Hunden. Als Material für den Liatest D-Di™ diente Zitratplasma, das bis zur Analyse bei –80 °C gelagert wurde. Die Messung mit dem Cardiac reader erfolgte mit heparinsierten frischen (< 1 Stunde alten) Vollblutproben. Ergebnisse: Der mittlere Intra-assay-Variationskoeffizient (VK) betrug 6,13% (Range 2,2–10,0%) für den Liatest D-Di und 19,8% (Range 20,05–19,56%) für den Cardiac reader. Bei 20/41 Proben fanden sich D-Dimer-Konzentrationen, die den für den Liatest D-Di ermittelten oberen Referenzbereich von 0,4 μg/ml (n = 62 gesunde Hunde) überschritten. Die lineare Regressionsanalyse der logarithmierten Daten ergab eine mäßige Korrelation zwischen beiden Methoden (r = 0,78), allerdings wurden die Ergebnisse mit einer mittleren proportionalen Mittelwertabweichung (Bias) von 0,45 μg/ml unterschätzt. Die Fläche unter der Receiver-Operating-Characteristic-(ROC-)Kurve betrug 0,895 hinsichtlich der Erkennung erhöhter Fibrin-D-Dimer-Werte mit dem Cardiac reader (Optimum 1,00). Bei einem Cut-off-Wert von > 0,2 μg/ml betrugen Sensitivität/Spezifität 85%/91% und das positive/negative Wahrscheinlichkeitsverhältnis (likelihood ratio) 8,93 und 0,17. Bei einem niedrigeren Cut-off-Wert von 0,15 μg/ml lagen Sensitivität und Spezifität bei 90% bzw. 66%. Schlussfolgerung und klinische Relevanz: Der Cardiac reader^® kann als Notfallanalysegerät für die quantitative Bestimmung kaniner D-Dimere verwendet werden. Berücksichtigt werden müssen jedoch die Möglichkeit falsch negativer Resultate und die im Vergleich zu einem Großgerät hohe Impräzision, sodass der Vergleichsmethode der Vorzug gegeben werden sollte.

Key words

Canine - disseminated intravascular coagulation - sensitivity - specificity - method validation

Schlüsselwörter

Kanin - Verbrauchskoagulopathie - Sensitivität - Spezifität - Methoden-validierung

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