Factor analysis of the interrelationships between clinical variables in horses with colic

A prospective survey of horses with colic referred to the Large Animal Hosp ital at the Royal Veterinary and Agricultural University of Copenhagen. Den mark. was undertaken between August 1994 and December 1997. The interrelati onships between 17 clinical variables were analysed using Factor analysis. Factor analysis uncovers the structure of the variability in data and there fore detects multicollinearity. A total of 528 horses were admitted in the study period. Of these. 16 were excluded from the analysis as a result of m iscellaneous conditions. Only 205 horses had observations for all 17 variab les. Because no major change occurred in the main diagnostic categories, th is population was considered as a representative subset. Factor analysis co nfirmed the clinical impression of correlation between variables. but the m ulticollinearity turned out not to he strong. Four factors were extracted, and these accounted for 51% of the total variance. The retained factors wer e interpreted by integrating previously reported clinical research. The fir st factor, which was interpreted as endotoxaemia, had high loadings on capi llary refill time, mucous-membrane colour, degree of pain, heart rate, pack ed-cell volume and abdominal sounds. In the second factor. cecal decompress ion. admission month and gastric reflux had the predominant influence, and this factor was explained as cecal tympany. The third factor was simply int erpreted as age because it had high loadings on gender, age and temperature . In the fourth factor, the interpretation was not straightforward. althoug h breed had the greatest influence in the formation of this factor. subsequ ently, the extracted factors were used in a logistic-regression analysis to determine their association with outcome (survival/death). The two factors interpreted as endotoxaemia and age were related to the outcome. (C) 2001 Elsevier Science B.V. All rights reserved.