Use of a multivariable model to estimate the probability of discharge in hospitalized foals that are 7 days of age or less

Barton W. Rohrbach Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Benjamin R. Buchanan Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Jennifer M. Drake Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Frank M. Andrews Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Fairfield T. Bain Hagyard Equine Medical Institute, 4250 Iron Works Pike, Lexington, KY 40511.

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Douglas T. Byars Hagyard Equine Medical Institute, 4250 Iron Works Pike, Lexington, KY 40511.

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William V. Bernard Rood and Riddle Equine Hospital, 2150 Georgetown Rd, Lexington, KY 40511.

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Martin O. Furr Marion DuPont Scott Equine Medical Center, 17690 Old Waterford Rd at Morven Park, PO Box 1938, Leesburg, VA 20177.

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Mary Rose Paradis Department of Clinical Sciences, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Jacquelin Lawler Peterson Smith Equine Hospital, 4747 Southwest 60th Ave, Ocala, FL 34474.

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Steeve Giguère Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

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Bettina Dunkel New Bolton Center Campus, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.

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Abstract

Objective—To create a mathematical model to assist in early prediction of the probability of discharge in hospitalized foals ≤ 7 days old.

Study Design—Prospective study.

Animals—1,073 foals.

Procedures—Medical records from 910 hospitalized foals ≤ 7 days old for which outcome was recorded as died or discharged alive were reviewed. Thirty-four variables including historical information, physical examination findings, and laboratory results were examined for association with survival. Variables associated with being discharged alive were entered into a multivariable logistic regression model. Accuracy of the model was validated prospectively on data from 163 foals.

Results—Factors in the final model included age group, ability to stand, presence of a suckle reflex, WBC count, serum creatinine concentration, and anion gap. Sensitivity and specificity of the model to predict live discharge were 92% and 74%, respectively, in the retrospective population and 90% and 46%, respectively, in the prospective population. Accuracy of an equine clinician's initial prediction of the foal being discharged alive was 83%, and accuracy of the model's prediction was 81%. Combining the clinician's prediction of probability of live discharge with that of the model significantly increased (median increase, 12%) the accuracy of the prediction for foals that were discharged and nonsignificantly decreased (median decrease, 9%) the accuracy of the predication for nonsurvivors.

Conclusions and Clinical Relevance—Combining the clinician's initial predication of the probability of a foal being discharged alive with that of the model appeared to provide a more precise early estimate of the probability of live discharge for hospitalized foals.

Abstract

Objective—To create a mathematical model to assist in early prediction of the probability of discharge in hospitalized foals ≤ 7 days old.

Study Design—Prospective study.

Animals—1,073 foals.

Procedures—Medical records from 910 hospitalized foals ≤ 7 days old for which outcome was recorded as died or discharged alive were reviewed. Thirty-four variables including historical information, physical examination findings, and laboratory results were examined for association with survival. Variables associated with being discharged alive were entered into a multivariable logistic regression model. Accuracy of the model was validated prospectively on data from 163 foals.

Results—Factors in the final model included age group, ability to stand, presence of a suckle reflex, WBC count, serum creatinine concentration, and anion gap. Sensitivity and specificity of the model to predict live discharge were 92% and 74%, respectively, in the retrospective population and 90% and 46%, respectively, in the prospective population. Accuracy of an equine clinician's initial prediction of the foal being discharged alive was 83%, and accuracy of the model's prediction was 81%. Combining the clinician's prediction of probability of live discharge with that of the model significantly increased (median increase, 12%) the accuracy of the prediction for foals that were discharged and nonsignificantly decreased (median decrease, 9%) the accuracy of the predication for nonsurvivors.

Conclusions and Clinical Relevance—Combining the clinician's initial predication of the probability of a foal being discharged alive with that of the model appeared to provide a more precise early estimate of the probability of live discharge for hospitalized foals.

Contributor Notes

Dr. Buchanan's present address is Brazos Valley Equine Hospital, 6999 Hwy 6, Navasota, TX 77868.

Dr. Byars' present address is 2183 Ironworks Pike, Georgetown, KY 40324.

Dr. Bernard's present address is Equine Internal Medicine, 4901 Mt Horeb, Lexington, KY 40511.

Dr. Lawler's present address is Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

Supported by the Department of Large Animal Clinical Sciences and Center of Excellence, University of Tennessee.

The authors thank Dr. Jennifer Collins for assistance with data collection and Dr. Arnold Saxton for statistical consultation.

Address correspondence to Dr. Rohrbach.
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