Consistency of results from the Vettest 8008 clinical biochemistry analyser

Analytic and quality control validation and assessment of field performance of a point-of-care chemistry analyzer for use in the White rhinoceros

BACKGROUND

A chemistry point-of-care analyzer would be useful for evaluating injured wildlife, particularly White rhinoceros (Ceratotherium simum) that survive poaching attempts. The IDEXX VetTest could be suitable, but species-specific validation, development of a statistical quality control (QC) strategy, and evaluation under field conditions are necessary.

OBJECTIVES

The objectives were to (1) validate the VetTest for the White rhinoceros, (2) perform QC validation on the VetTest and generate a statistical QC strategy, and (3) apply this QC strategy to monitor performance under typical field conditions.

METHODS

Differences between White rhinoceros heparin plasma and serum, short-term imprecision, and reportable range using rhinoceros plasma and long-term imprecision using commercial quality control material (QCM) were assessed against prescribed total allowable error (TE_a ) for up to 15 analytes. Quality control validation was performed using data from the long-term imprecision study and TE_a . A QC strategy using QCM was developed and used to monitor performance under field conditions.

RESULTS

Imprecision was acceptable for all analytes except for ALP, ALT, and AST at low activities. The reportable range for AST and LDH differed from the manufacturer's specifications. Eleven analytes were suitable for statistical QC using the 1_3s rule, 3 using the 2_s rule; ALP was not suitable. In the field, observed error was < TE_a for all 15 analytes and the sigma metric was > 3.0 for 12 analytes.

CONCLUSIONS

The VetTest is suitable for use in the White rhinoceros. Statistical QC is possible for most analytes and useful for evaluation of field performance.

The effects of haemolysis on serum chemistry measurements in poultry

The effects of haemolysis on serum chemistry values in broiler and layer chickens, and in turkeys were determined using two types of serum chemistry analysers, a wet reagent analyser and a dry slide reagent analyser. The interfering effects of haemolysis were evaluated using eight levels of haemoglobin in serum analysed by the wet reagent instrument and six levels of haemoglobin in serum analysed by the dry slide reagent instrument. Nine serum chemistry analytical tests were performed on each analyser, including determination of glucose, total protein, albumin, creatine kinase, gamma-glutamyl transferase, aspartate aminotransferase, calcium, phosphorus and uric acid. The interfering effects of haemolysis varied depending on type of analyser, type of bird and the specific test. With the wet reagent chemistry analyser, the gamma-glutamyl transferase, phosphorus and uric acid analytes were most sensitive to haemoglobin interference, and the albumin, total protein and creatine kinase analytes were most resistant. With the dry slide reagent analyser, the gamma-glutamyl transferase, phosphorus, and albumin analytes were most sensitive to haemoglobin interference, and the glucose and aspartate aminotransferase analytes were most resistant. The effects of haemoglobin interference were not consistent from one type of chemistry analyser to another. The dry slide reagent analyser did not appear to resist the effects of haemoglobin interference better than the wet reagent analyser in this study. Our results suggest the need to construct interferographs for each chemistry analyser, species, and type of bird.

Long-term motility and fertility conservation of chilled canine semen using egg yolk added Tris–glucose extender: In vitro and in vivo studies

The effects of medium exchange on motility parameters of chilled canine semen preserved in egg yolk Tris-glucose (EYTG) extender were analyzed over a 27-d period. Semen extender was exchanged at three time points (Days 11, 21 and 27) after collection, when motility parameters were demonstrated to significantly decrease from parameters observed at semen preparation (Day 0) or at day of previous extender exchange. In the absence of medium exchanges, motile spermatozoa were observed up to Day 16 (mean +/- S.D. 1.5 +/- 0.3% of motile spermatozoa). A stimulation of the different semen motility parameters was observed after extender exchange. Semen extender exchange at Day 11 allowed conservation of motility until Day 21, compared to 16 d in the absence of extender exchange. At Day 21, when spermatozoa appeared immobile or dead, a second extender exchange was performed, allowing the extension of motility conservation up to Day 27. The third extender exchange, performed at Day 27, was no longer associated with motility stimulation. Glucose content in the medium decreased slowly over time; a concomitant decrease in pH was also observed. No changes in osmolarity were observed over time. To verify the fertility of long-term conserved chilled semen, two groups of 10 bitches were inseminated either once (Group 1) or twice at 48-h intervals (Group 2) intra-vaginally with semen conserved chilled for a mean of 9 +/- 1.8 d. Out of the 10 bitches inseminated once, 5 became pregnant, versus 7 in the group of animals inseminated twice. The present study reports the possibility to extend the conservation of chilled canine semen up to 3 wk with conservation of good fertility for at least 10 d. The role of energetic substrate and pH alteration is postulated and the classically accepted relation of semen motility/viability is raised.

Effects of hemolysis on serum chemistry analytes in ratites

Since hemolysis has been a common problem in submitted ratite serum samples, a study was performed to determine interference by hemolysates. Nine chemistry analytes including glucose, total protein, albumin, creatine kinase (CK), gamma-glutamyl transferase (GGT), aspartate aminotransferase (AS7), calcium (Ca), phosphorus, and uric acid were evaluated on a wet reagent analyzer (Ciba Corning Express 550) and on a dry slide reagent analyzer (VetTest 8008). In emus, increasing hemoglobin concentrations increased total protein, albumin, and CK for both analyzers. With increasing hemoglobin concentrations, the Ciba Corning 550 analyte values were increased for AST, Ca, and uric acid and decreased for glucose and phosphorus, the opposite effect was seen in values from the VetTest 8008. GGT levels were variable or sometimes undetectable. Changes in ostrich analytes with hemolysis were similar to emus using the same analyzer. The effects of serum hemolysis often differed in magnitude and direction between the two chemistry analyzers. Interferographs were constructed to aid in rapid assessment of the effects of hemolysis on submitted serum samples.

Application of the Vettest 8008 system for the biochemical analysis of vervet monkey plasma

A clinical biochemistry analyser designed specifically for veterinary use was used to analyse plasma samples from 24 vervet monkeys (Cercopithecus aethiops). Two millilitres of heparinised blood was collected from each of the 24 monkeys on four occasions at intervals of one week. Plasma was separated and analysed for the concentrations of triglycerides, cholesterol, total proteins, albumin, globulins, creatinine and blood urea nitrogen (BUN) and the activities of alkaline phosphatase (AP), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatine kinase (CK). The tests were easy to perform, used small volumes of plasma, and yielded consistent results for most of the analytes. The activities of CK and AP, but not AST, appeared to be influenced by haemolysis, and there were significant individual variations in the activity of LDH.

Application of probability techniques to the objective interpretation of veterinary clinical biochemistry data

Methods for the interpretation of veterinary clinical biochemistry have not developed as rapidly as biochemical technology. However, the results of clinical biochemistry tests are only of value when they are interpreted appropriately. A retrospective study was undertaken to investigate the equine biochemistry data which had been stored in a veterinary hospital database. By applying percentile analysis and Bayesian probability methods to the clinical biochemistry and corresponding diagnosis data, a novel method for the interpretation of clinical biochemistry data has been developed. The method allows clinicians to determine whether a biochemistry value is abnormal, its degree of abnormality, and the most likely associated diagnoses. The method could be used to investigate a practice-based population and may have significant implications for the interpretation of clinical biochemistry data in veterinary medicine in the future.

Objective interpretation of bovine clinical biochemistry data: application of Bayes law to a database model

With the advent of animal-side biochemistry analysers in veterinary practice, the requirement for ready access to reliable means for interpretation of the results is of increasing importance. At the University of Glasgow Veterinary School (GUVS), a large computerised hospital database containing extensive clinical, laboratory, and pathological information has been maintained. A retrospective study was undertaken to investigate plasma biochemistry results and corresponding post mortem diagnosis data from 754 unwell cattle which had presented to GUVS over the study period. Initial analysis of the clinical biochemistry data from this unwell population revealed that the parameters did not follow a normal distribution. This finding suggested that the accepted reference range method for the interpretation of clinical biochemistry data may provide limited information about the unwell animal. By applying a combination of percentile analysis and conditional probability techniques to the hospital data, the development of a means of clinical biochemistry interpretation was developed whereby a clinician could determine whether a value was abnormal, the degree of abnormality, and the most likely associated diseases. For example, a urea value of 30 mmol/l lay within the top 5% of results, and one of the most common diseases associated with this urea value was pyelonephritis. Furthermore, a Bayesian approach allowed the quantification of the relationship between any plasma biochemistry value and disease through the generation of a ratio termed the 'biochemical factor'. Using the same example, given a urea value of 30 mmol/l, pyelonephritis was eight times more likely than before any biochemistry information was known. The results from the study were used to form the basis of a software system which may ultimately be used by the clinical to aid in the recognition, treatment and prevention of disease in the veterinary domain.

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.