Evaluation of an automated serum bile acids assay and the effect of bilirubin, hemoglobin, and lipid on the apparent bile acids yield

Verification of bile acid determination method and establishing reference intervals for biochemical and haematological parameters in third-trimester pregnant women

OBJECTIVES

The aims of this study were to verify the bile acids (BA) method and to establish reference intervals (RIs) for bile acids (BA) and biochemical and haematological parameters in Croatian pregnant women.

METHODS

BA spectrophotometric method verification was performed on Siemens Atellica Solution CH 930 automated analyser using Sentinel reagent. Stability, precision, trueness, linearity, and RIs, as well as lipemia interference were tested according to CLSI guidelines. BA, biochemical, and haematological parameters were measured in serum (BA, biochemical) and whole blood (haematological) samples of fasting healthy third-trimester pregnant women from Croatia (n=121). The establishment of the RIs was done a priori according to the CLSI EP28-A3C:2010 guideline. Selected reference individuals' data were analysed using parametric, non-parametric, and robust methods.

RESULTS

Stability study showed that BA are stable in serum samples for 2 days at 20 °C, 14 days at 4-8 °C, and 22 days at -20 °C. The precision study and adult RIs verification met the criteria. Linearity was verified for the concentration range of 3.5-172.1 μmol/L whereas the lipemia interference test showed a positive bias (%) in BA concentration. The determined reference limits generally exhibited better precision for haematological parameters, being lower than the upper recommended value 0.2, unlike biochemical parameters. Haematological parameters showed notable differences between pregnant and non-pregnant women, while many biochemical parameters' RIs remained similar. Only ALT and GGT showed lower non-comparable RI upper limits in the population pregnant women.

CONCLUSIONS

Spectrophotometric BA method showed satisfactory performance and all examined parameters were within the set criteria. Moreover, RIs for key biochemical and haematological parameters, including BAs, have been established for the first time in the population of Croatian pregnant women.

Partial analytical validation of the VetScan cPL rapid test

BACKGROUND

Serum canine pancreatic lipase immunoreactivity (cPLI) concentrations have become the standard laboratory test used to diagnose canine pancreatitis. Recently, a new point-of-care assay for cPLI, the VetScan cPL rapid test (VetScan cPL), has become available, but analytical validation data have not yet been published.

OBJECTIVE

This study aimed to perform a partial analytical validation of the VetScan cPL.

METHODS

Leftover serum samples from a diagnostic laboratory were used. Adherence to the manufacturer's guidelines, linearity, repeatability, and reproducibility were evaluated. Results of the VetScan cPL were correlated with the Spec cPL results.

RESULTS

Observed-to-expected ratios for dilutional parallelism ranged from 77.4% to 162.9% (mean 119.3%). Intra-assay and inter-assay variabilities ranged from 16.9% to 36.7% (mean 25.1%) and from 14.1% to 51.2% (mean 31.8%), respectively. Adherence to the manufacturer's specification regarding results within ± 60 µg/L of the Spec cPL result was only achieved for 39% of the measurements. The VetScan cPL and Spec cPL correlation showed a Spearman's r of .758 for 29 data pairs.

CONCLUSIONS

Under the conditions of this study, the VetScan cPL did not adhere to the manufacturer's specifications for most measurements. Also, the VetScan cPL showed suboptimal linearity and was not precise. In conclusion, the VetScan cPL failed basic analytical validation.

Evaluation of a semiquantitative SNAP test for measurement of bile acids in dogs

Background. Serum bile acids (SBA) are used as a routine screening tool of liver function in dogs. Serum samples are usually shipped to a referral laboratory for quantitative analysis with an enzymatic chemistry analyzer. The canine SNAP Bile Acids Test (SNAP-BAT) provides an immediate, semi-quantitative measurement of bile acid concentrations in-house. With the SNAP-BAT, bile acids concentrations of 5–30 µmol/L are quantified, and results outside of that range are classified as <5 or >30 µmol/L. Agreement of the SNAP-BAT with the enzymatic method has not been extensively investigated.

Objectives. The purposes of this prospective clinical study were to assess the precision of the SNAP-BAT and determine agreement of SNAP-BAT with results from an in-house chemistry analyzer.

Methods. After verifying intra-assay precision of the SNAP-BAT, a prospective analysis was performed using blood samples collected from 56 dogs suspected to have liver disease. Each sample was analyzed with an enzymatic, in-house chemistry analyzer and the SNAP-BAT. Agreement between the two methods was statistically assessed using the κ index of agreement.

Results. Intra-assay variability was minimal. The κ index for agreement between the SNAP-BAT and routine chemistry analyzer was between 0.752 and 0.819, indicating substantial to near perfect agreement.

Conclusions. The SNAP-BAT is a highly accurate, semi-quantitative test that yields immediate results, and has very little intra-assay variability, particularly for results >30 µmol/L.

Interlaboratory agreement and handling variability for consistency of results in paired serum bile acid assays

Paired serum bile acid (SBA) samples from 30 dogs with presumptive hepatobiliary disease and 30 apparently healthy dogs were submitted to three diagnostic laboratories to validate agreement between these facilities. Sensitivities and specificities ranged from 50% to 70% and from 74% to 85%, respectively, for all laboratories. The κ index confirmed almost perfect agreement between laboratories. Variation in sample handling and processing by different laboratories should not be considered a primary factor when aberrant SBA values are encountered. Documenting agreement between laboratories is essential as inconsistencies could direct unnecessary medical or surgical intervention when patients are evaluated at different hospitals during the course of their disease.

Post-prandial serum bile acid concentrations and ammonia tolerance in Maltese dogs with and without hepatic vascular anomalies

Post-prandial serum bile acid concentrations were measured in 200 Maltese dogs in an attempt to identify those with subclinical portosystemic shunts. Five of these were later shown to have hepatic pathology or abnormal liver function. In the other 195 Maltese, bile acid concentrations ranged from 1 to 362 mumol.L-1 (mean +/- SD, 70 +/- 50 mumol.L-1; median, 65.0 mumol.L-1). Of these, 79% were above the reference range (0 to 31 mumol.L-1) established from 23 mixed-breed control dogs. It was therefore not possible to determine the prevalence of subclinical portosystemic shunts on the basis of bile acid determinations. Further investigation of liver function was performed to investigate why bile acid concentrations were increased in these dogs. Rectal ammonia tolerance tests were normal in 102 of 106 Maltese tested and liver samples (11 dogs) and plasma biochemistry profiles (9 dogs) demonstrated no significant hepatic disease or dysfunction. Of 2 Maltese with hyperammonaemia after administration of ammonium chloride, one had a large congenital portosystemic shunt that was confirmed at surgery. In the other there were no macroscopic portosystemic communications, but a liver biopsy showed histological changes consistent with microscopic portovascular dysplasia. Total serum bile acid concentrations were consistently lower when assessed by high-performance liquid chromatography than by an enzymatic spectrophotometric method. This discrepancy was substantially larger in Maltese than in control dogs, suggesting the presence of an additional reacting substance in the serum of Maltese dogs.