Comparison of a commercially available veterinary digital refractometer to analogue refractometer and laboratory chemistry analyzer in the evaluation of canine serum total protein.

OBJECTIVE: To assess the agreement between measurements of total protein (TP) concentrations in canine serum samples between a commercially available veterinary digital refractometer (DR), an analog handheld refractometer (AR), and a laboratory-based chemistry analyzer (LAB). An additional objective was to assess the effects of various potential interferents (ie, hyperbilirubinemia, increased BUN, hyperglycemia, hemolysis, and lipemia) on DR measurements. SAMPLE: 108 canine serum samples. PROCEDURES: Serum samples were measured in duplicate on the DR, which reported TP concentration, assessed via optical reflectance and critical angle measurement. These serum samples were also assessed on the AR and LAB for comparison. Serum samples with grossly visible lipemia, hemolysis, and icterus were noted. Medical records were retrospectively assessed to determine concentrations of BUN, glucose, and bilirubin. RESULTS: Method comparisons among the various data generated by the analyzers were completed using linear regression, Bland Altman, and calculation of intraclass coefficients. Mean bias between DRTP and LABTP in samples without potential interferents was 0.54 g/dL with 95% limits of agreement of -0.17 to 1.27 g/dL. One-third of DRTP samples without potential interferents had > 10% difference from their LABTP comparison. Interferents, particularly marked hyperglycemia, can result in inaccurate measurements on the DR. CLINICAL RELEVANCE: There was a statistically significant difference between DRTP and LABTP measurements. TP measurements in samples with any potential interferent, particularly hyperglycemia, should be assessed cautiously on DR and AR.

Effects of potential confounding variables on accuracy of a commercially available veterinary point-of-care hematocrit meter in the evaluation of blood samples from dogs and cats.

OBJECTIVE: To assess the agreement in measurements of Hct values and hemoglobin (Hgb) concentrations in blood samples from dogs and cats between a commercially available veterinary point-of-care (POC) Hct meter and a laboratory-based (LAB) analyzer and to determine the effects of various conditions (ie, lipemia, hyperbilirubinemia, hemolysis, autoagglutination, and reticulocytosis) on the accuracy of the POC meter. SAMPLES: Blood samples from 86 dogs and 18 cats. PROCEDURES: Blood samples were run in duplicate on the POC meter, which reported Hgb concentration, measured via optical reflectance, and a calculated Hct value. The POC meter results were compared with results from a LAB analyzer. Blood samples with grossly visible lipemia, icterus, hemolysis, and autoagglutination were noted. RESULTS: Mean ± SD values for LAB Hct were 33.9 ± 15.73% (range, 3.9% to 75.8%), and for LAB Hgb were 11.2 ± 5.4 g/dL (range, 1 to 24.6 g/dL). Mean bias between POC Hct and LAB Hct values was -1.8% with 95% limits of agreement (LOAs) of -11.1% to 7.5% and between POC Hgb and LAB Hgb concentrations was -0.5 g/dL with 95% LOAs of -3.8 to 2.8 g/dL. There was no influence of lipemia (14 samples), icterus (23), autoagglutination (14), hemolysis (12), or high reticulocyte count (15) on the accuracy of the POC meter. The POC meter was unable to read 13 blood samples; 9 had a LAB Hct ≤ 12%, and 4 had a LAB Hct concentration between 13% and 17%. CONCLUSIONS AND CLINICAL RELEVANCE: Overall, measurements from the POC meter had good agreement with those from the LAB analyzer. However, LOAs were fairly wide, indicating that there may be clinically important differences between measurements from the POC meter and LAB analyzer.