Jensen A L, Houe H, Nielsen C G
Department of Clinical Studies, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Acta Vet Scand. 1992;33(3):211-7. doi: 10.1186/BF03547311.
The purpose of the present study was to calculate the critical difference between 2 analytical results for the red blood cell count (RBC), the white blood cell count (WBC), the haemoglobin concentration (Hb), and the haematocrit (PCV) in blood from Red Danish Dairy cows. The critical difference can help to judge whether the difference between 2 consecutive analytical results from the same animal may be safely ascribed to natural variation or not. To calculate the critical differences, blood samples from 20 clinically healthy lactating cows were collected once daily for 5 consecutive days. The total variance of the analytical results was divided into the component of variance between cows (S2Inter), the component of variance for days within cows (S2Intra), and the component of variance for measurements (S2Anal) using nested analysis of variance. The critical difference was then calculated from S2Intra and S2Anal as 0.61 x 10(12)/l for RBC, 2.2 x 10(9)/l for WBC, 0.79 mmol/l for Hb, and 0.07 for PCV. The critical differences may be used as guidelines to indicate potentially important changes in the parameters. However, the analytical results should not be assessed by the critical differences alone, but should also be compared to the corresponding reference intervals.
本研究的目的是计算丹麦红牛血液中红细胞计数（RBC）、白细胞计数（WBC）、血红蛋白浓度（Hb）和血细胞比容（PCV）两项分析结果之间的临界差值。该临界差值有助于判断同一动物连续两次分析结果之间的差异是否可安全归因于自然变异。为计算临界差值，连续5天每天采集20头临床健康泌乳奶牛的血样。使用嵌套方差分析将分析结果的总方差分为奶牛间方差成分（S2Inter）、奶牛内天数方差成分（S2Intra）和测量方差成分（S2Anal）。然后根据S2Intra和S2Anal计算出的临界差值为：RBC为0.61×10¹²/l，WBC为2.2×10⁹/l，Hb为0.79 mmol/l，PCV为0.07。这些临界差值可作为指标，指示参数中潜在的重要变化。然而，分析结果不应仅通过临界差值来评估，还应与相应的参考区间进行比较。
