Application of the ASVCP guidelines for the establishment of haematologic and biochemical reference intervals in Icelandic horses in Austria.

Background: Despite the increasing popularity of Icelandic horses, published reference intervals (RIs) in this breed are rare. Due to their isolation and their small gene pool, alterations in some variables are likely and some possible breed-specific peculiarities have been described. The purpose of the present study was the establishment of comprehensive RIs in Icelandic horses according to recently published guidelines. In a prospective observational study, blood samples were collected from the jugular vein of 142 Icelandic horses into EDTA and serum tubes. Reference intervals were established for haematologic and biochemical analytes on the Advia 2120i™ and the Dimension ExL™ by established methods. RIs were defined as central 95 % intervals bounded by the 2.5th and 97.5th percentiles with their 90 % confidence intervals, calculated according to recently published ASVCP guidelines. An inhouse-developed quality control system using observed total allowable error was used for the surveillance of the internal quality control preceding the measurements.

Results: The RIs were as follows: haematocrit: 0.29-0.39, RBC: 5.79-8.63 T/l, haemoglobin: 102.0-142.3 g/l, MCV: 42-51 fl, platelets: 146-263 G/l, WBC: 4.13-8.57 G/l, segs: 1.98-4.73 G/l, lymphocytes: 1.25-3.49 G/l, monocytes: 0.06-0.31 G/l, eosinophils: 0.04-0.50 G/l, glucose: 4.0-5.7 mmol/l, urea: 3.2-6.4 mmol/l, creatinine: 79.6-141.4 μmol/l, total protein: 54.4-72.9 g/l, albumin: 27.7-36.8 g/l, total bilirubin: 8.1-21.1 μmol/l, triglycerides: 0.03-0.44 mmol/l, cholesterol: 1.75-2.90 mmol/l, ALP: 1.35-3.55 μkat/l, AST: 4.52-8.80 μkat/l, GLDH: 0.0-0.18 μkat/l, GGT: 0.11-0.39 μkat/l, CK: 2.53-6.52 μkat/l, LDH: 3.32-7.95 μkat/l, iron: 16.4-39.9 μmol/l, calcium: 2.69-3.19 mmol/l, phosphate: 0.5-1.3 mmol/l, magnesium: 0.6-0.9 mmol/l, sodium: 134-141 mmol/l, potassium: 3.6-4.7 mmol/l, chloride: 100-105 mmol/l.

Conclusions: Reference intervals of several haematologic and biochemical analytes differed from the transferred historical reference intervals applied to equine samples in the authors' laboratory. These might be of clinical importance in some analytes such as creatine kinase.