Evaluation eines neuen elektronischen Handmess geräts zur Messung von β-Hydroxybutyrat bei Milchkühen

Zusammenfassung

Gegenstand und Ziel: Die subklinische Ketose (SCK), eine weitverbreitete Stoffwechselkrankheit frischlaktierender Milchkühe, ist definiert durch das Auftreten erhöhter Mengen zirkulierender Ketonkörper bei Fehlen klinischer Symptome. Daher beschränken sich die Möglichkeiten der Diagnostik auf den Nachweis dieser Ketonkörper in verschiedenen Körperflüssigkeiten. Ziel der Studie war die Evaluation eines neuen elektronischen mobilen Messgeräts (NovaVet) zur Messung von β-Hydroxybutyrat (BHB) im Nativblut von Milchkühen. Material und Methoden: Anhand von Blutproben von 155 laktierenden Milchkühen erfolgte ein Vergleich zwischen den mit dem Gerät ermittelten und den in einem kommerziellen Labor gemessenen BHB-Konzentrationen. Zur Auswertung wurden der Rangkorrelationskoeffizient nach Spearman bestimmt, ein Wilcoxon-Test durchgeführt und die gepaarten Messwerte nach Bland und Altman graphisch dargestellt. Ferner wurden für das Gerät spezifische BHB-Grenzwerte im Vergleich zu international anerkannten Grenzwerten zur Diagnose einer SCK mithilfe einer Receiver-Operating-Characteristic(ROC)-Analyse ermittelt und die entsprechenden Testcharakteristika bestimmt. Ergebnisse: Zwischen den vom Gerät und den im Labor gemessenen BHB-Konzentrationen bestand eine hohe Korrelation (r_s = 0,87; p < 0,05). Die vom Gerät (Median 1,0 mmol/l; Interquartilsabstand [IQR] 0,7–1,3 mmol/l) und im Labor (Median 0,9 mmol/l; IQR 0,7–1,1 mmol/l) gemessenen BHB-Konzentrationen differierten (Median 0,0 mmol/l; IQR –0,1 bis 0,2 mmol/l; p < 0,05). Mit dem Gerät konnte eine SCK bei einem Grenzwert von 1,2 mmol/l BHB mit einer Sensitivität von 97% und einer Spezifität von 82% diagnostiziert werden. Als Goldstandard diente der Laborwert. Schlussfolgerung und klinische Relevanz: Das BHB-Messgerät zeigte eine gute Übereinstimmung mit dem Labor und gute Testeigenschaften. Seine geringfügige Messabweichung im Vergleich zum Labor kann unter praktischen Bedingungen vernachlässigt werden, doch muss mit einer gewissen Anzahl falsch als erkrankt diagnostizierter Tiere gerechnet werden. Das Gerät kann für die Dia gnostik der SCK beim Rind empfohlen werden.

Summary

Objective: Subclinical ketosis (SCK), an important disease in lactating dairy cows, is defined as the presence of elevated concentrations of circulating ketone bodies without the development of clinical signs. Therefore, diagnostic methods are limited to the detection of the concentrations of ketone bodies in different body fluids. The objective of this study was to evaluate a recently developed electronic handheld meter (NovaVet) for the determination of β-hydroxybutyric acid (BHB) in the blood of dairy cows. Material and methods: A total of 155 lactating dairy cows were included in the trial. Blood samples were taken from each cow and analyzed using the BHB meter. The obtained concentrations were compared to the results determined by a commercial laboratory. The Spearman’s rank correlation coefficient was determined between the two methods. A Wilcoxon test was performed and a Bland-Altman plot was generated. Test characteristics (sensitivity, specificity, positive and negative predictive value) for established BHB cut points for the diagnosis of SCK were calculated using receiver operating characteristic (ROC) analysis. Results: The two methods were highly correlated (r_s = 0.87; p < 0.05). A difference (median 0.0 mmol/l; interquartile range [IQR] –0.1 to 0.2 mmol/l; p < 0.05) was found between BHB concentrations determined using the BHB meter (median 1.0 mmol/l; IQR 0.7–1.3 mmol/l) and by the laboratory (median 0.9 mmol/l; IQR 0.7–1.1 mmol/l). Using a cut point of 1.2 mmol/l, sensitivity and specificity of the BHB meter were 97% and 82%, respectively. Conclusion and clinical relevance: There was a good agreement between BHB concentrations determined using the BHB meter and the laboratory. Furthermore, the BHB meter displayed good test characteristics. The specificity of 82% results in a number of false-positive results. However, this new device can be recommended for the detection of SCK in cows under practical conditions.

Schlüsselwörter

Subklinische Ketose - Handgerät - Bestandsüberwachung - Herdengesundheit - Stoffwechsel - Hyperketonämie

Key words

Subclinical ketosis - handheld device - monitoring - herd health - metabolism - hyperketonemia

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