Reference intervals for hematologic and coagulation tests in adult alpacas (Vicugna pacos).

BACKGROUND

Species-specific reference intervals are needed for interpretation of laboratory tests. Reference interval studies of alpacas have been limited by low numbers and use of outdated methods.

OBJECTIVES

The aims of this study were to establish reference intervals for hematologic and coagulation tests in alpacas using a laser-based hematology analyzer and a mechanical clot detection coagulation analyzer, respectively; to compare results for automated and manual differential WBC and platelet counts and fibrinogen concentrations; and to examine the effect of herd and sex on hematologic tests in a population of alpacas.

METHODS

Blood collected from clinically healthy female and male adult alpacas (Vicugna pacos) from 5 herds underwent full CBC analysis using an ADVIA 2120 (n = 65). Blood smears were examined for manual differential WBC counts, platelet estimates, and morphologic examination of blood cells. PCV and plasma protein and heat-precipitable fibrinogen concentration measured by refractometry were also determined. Partial thromboplastin time, prothrombin time, and clottable fibrinogen concentration were measured using a STA Compact analyzer (n = 13). Reference intervals were established using 2.5th and 97.5th percentiles for hematologic analytes and minimum and maximum values for coagulation tests. Automated and manual differential WBC counts, platelet counts, and fibrinogen concentrations were compared. Results were also evaluated for herd- and sex-associated effects.

RESULTS

Hematologic reference intervals for alpacas were similar to those reported previously, except for lower RBC-related results, which showed a herd bias. Correlations between automated and manual neutrophil, lymphocyte, eosinophil, and platelet counts were moderate to good, with weak to poor correlations for monocyte and basophil counts and fibrinogen concentrations. Owing to the low number of samples analyzed, reference intervals for coagulation tests should be considered estimated intervals.

CONCLUSIONS

Reference intervals will be useful guides for interpreting hematologic and coagulation results in alpacas, particularly when using the same instrumentation and reagents.