Fastställande av referensintervall för fibrinogen i plasma hos friska föl

Abstract: Fibrinogen concentrations were analysed in EDTA preserved blood plasma samples from 34 thoroughbred foals born in 2001 and 2002 at one stud farm. The foals were between 0 and 240 days old at the time of the sampling, and there were 19 fillies and 12 stallions in the group. The foals were examined for clinical symptoms of disease and their body temperature was measured before blood was sampled from the jugular vein. From totally 156 blood samples, 31 were selected as originating from clinically healthy foals, and used to determine a reference range for thoroughbred foals. Samples originating from foals showing clinical symptoms of disease or an abnormal body temperature at the time of sampling, were classified as coming from unhealthy animals. The samples were transported to the Department of Clinical Chemistry, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden. The fibrinogen concentration in plasma was determined using a commercial reptilase method (Fibrinogen Kinetic, F. Hoffmann-La Roche & Co, Diagnostica, Switzerland) and a Konelab 30 analyser (Konelab, Corporation, Espoo, Finland). The number of leukocytes was also determined in all samples (Cell-dyn 3500, Abott Diagnostics, Abott Park, IL, USA). The reference range (mean1.96 SD) for the studied group was estimated to 2.9-6.1 g/L (meanSD, 4.40.8 g/L). Although a small number of animals was used, the frequency distribution (Figure 1) indicated a normal distribution. Similar results were obtained when alternative methods were used to calculate a reference range. The estimated level of 2.9-6.1 g/L for the central 95% of this foal group is higher than the interval used for adult horses (1.8-4.2 g/L) in the present laboratory. This is important to consider when examining foals. A value that is evaluated as increased, may be perfectly normal for foals in general. Among the totally 31 clinically healthy foals, 19 (56%) showed increasing concentrations with age, 3 of them (9%) decreased, while 4 (12%) were unchanged. Sex did not seem to play any big role for fibrinogen levels when the 19 fillies and 12 stallions were compared. The fillies had a wider variation (min-max 2.6-6.3 for fillies, 3.6-5.5 for stallions, respectively), but the means for the two groups were comparable (4.5 g/L for fillies, 4.4 g/L for stallions). Fibrinogen development over time in foals with clinical disease was not thoroughly investigated. However, it seemed that the foals showing evidence of clinical disease, had the highest fibrinogen value at the first sampling occasion. This shows that fibrinogen is a fast reacting acute phase protein indicating an inflammatory reaction already when the owner first discovered signs of disease in this free ranging foals. Interestingly, this survey showed, that the fibrinogen levels of healthy foals did not differ much from the fibrinogen levels in foals with clinical disease. This underlines the importance for the veterinarian to always make a synthesis between clinical symptoms and results of blood analyses, as obviously some of the foals were ill when sampled although their fibrinogen levels were within the calculated reference range.