An update on chemistry analyzers.

This update of six chemistry analyzers available to the clinician discusses several points that should be considered prior to the purchase of equipment. General topics include how to best match an instrument to clinic needs and the indirect costs associated with instrument operation. Quality assurance recommendations are discussed and common terms are defined. Specific instrument features, principles of operation, performance, and costs are presented. The information provided offers potential purchasers an objective approach to the evaluation of a chemistry analyzer for the veterinary clinic.

Comparison of methods for sodium and potassium determination in llama urine.

OBJECTIVE: To compare results for sodium and potassium determination on llama urine, using flame emission spectrophotometry (flame photometry), atomic absorption spectrophotometry (AAS), indirect ion-selective electrode potentiometry (ISE), and direct ISE. DESIGN: Llama urine samples encompassing a wide range of electrolyte concentrations were analyzed for sodium and potassium concentrations, using 4 analytical methods, and results were compared statistically to assess correlation, bias, and potential interferents. SAMPLE POPULATION: 10 healthy male llamas. PROCEDURE: Urine specimens were obtained from llamas fitted with urine collection apparatus at defined intervals over a 24-hour period. Urine samples were centrifuged, and supernatants were frozen at -70 C until analysis. Analytical procedures were done, using standard laboratory protocols. Means, correlation coefficients, and bias were calculated, and differences were evaluated by ANOVA, with significance set at P < 0.05. RESULTS: There was strong correlation and good agreement among sodium values obtained by flame photometry, AAS, and indirect ISE. Sodium values obtained by use of direct ISE correlated poorly with other methods; urine is not an acceptable specimen for this method. Only AAS and indirect ISE had good correlation (r > 0.9) for potassium values. Data did not suggest presence of a potassium chelator in llama urine; urine potassium values measured by indirect ISE were significantly higher (by 150 to 200 mmol/L) than those measured by other methods. CLINICAL RELEVANCE: Urine electrolyte analysis in llamas resulted in less agreement between methods than is generally found for serum. Data collection for patient monitoring or research analysis should be restricted to a single method to avoid differences in results attributable to analytical variance.

Flow cytometric analysis of feline reticulocytes.

Hemolytic anemia was induced in five Domestic Shorthair cats (four adult males and one spayed female obtained from a breeding colony at Colorado State University, CO), and blood samples were analyzed from five other cats (two castrated male Domestic Shorthairs, one castrated male Domestic Longhair, one castrated male Persian, and one spayed female Siamese presented to the Veterinary Teaching Hospital at Colorado State University for miscellaneous problems). Blood samples taken from these cats had percentages of aggregate reticulocytes that ranged from 0% to 14.5% as determined by manual counting and were used to identify the best technique for staining cat reticulocytes for flow cytometric analysis. The best technique was mixing a blood sample (1/2,000 dilution) with 0.2 micrograms thiazole orange in 1 ml of diluent and incubating the mixture in the dark at room temperature for 30 to 60 minutes. The percentage of reticulocytes determined by flow cytometry correlated well (r = 0.88) with manually determined aggregate reticulocyte percentages; no significant differences were observed between the two techniques (P > 0.05). For the conditions used, punctate reticulocytes were not detected by flow cytometry. Samples with very high platelet numbers and very low packed cell volumes may show falsely elevated percentages of reticulocytes as determined by flow cytometry. The reproducibility of the flow cytometric technique was good; the coefficient of variation ranged from 4.8% to 17.9% in two samples with two different times of incubation. Staining of cat aggregate reticulocytes with thiazole orange and use of flow cytometric quantification is a reproducible technique that has a good correlation with the manual reticulocyte counting method.