Prognostic value of anion gap calculation in cattle with abomasal volvulus: 58 cases (1980-1985)

Values for anion gap, serum chloride, and base excess were tabulated for 58 dairy cows with abomasal volvulus. Test values for survivors (n = 40) and nonsurvivors (n = 18) were compared. Surviving cattle were released for production or salvage. Nonsurviving cows died or were euthanatized. Accuracy of preoperative anion gap, serum chloride, and base excess values in predicting outcome was evaluated by calculating the sensitivity, specificity, predictive value, and negative predictive value of these at assigned cutoff values. Anion gaps greater than or equal to 30 mEq/L were indicative of a poor prognosis. At this value, the sensitivity (0.889), specificity (0.925), predictive value (0.842), negative predictive value (0.949), and efficiency (0.914) were higher than when serum chloride concentration less than or equal to 84 mEq/L or base excess value less than or equal to 0 were used to denote poor prognosis. We concluded that preoperative anion gap calculation could reliably predict the outcome of cows with abomasal volvulus and was more accurate than either serum chloride concentration or base excess value.