A review of proficiency exercises offered by the Veterinary Laboratory Investigation and Response Network (Vet-LIRN) and Moffett Proficiency Testing Laboratory from 2012 to 2018

A novel proficiency test to assess the animal diagnostic investigation process in identifying an unknown toxicant

Participation in Proficiency Tests (PTs) is an important component of quality assurance in testing laboratories. In a typical chemistry PT, blind-coded samples are sent to participants for analysis of specific chemical agents, and results are compared to a pre-determined key (e.g., expected concentrations) to assess proficiency. In the animal diagnostic PT presented here, organizers evaluated not only the analytical component of the diagnostic investigation but also the entire investigative process as a multi-step, holistic multidisciplinary approach. Fourteen veterinary diagnostic laboratories (VDLs) participated in an exercise to identify the root cause of a simulated case of lead (Pb) toxicosis. VDLs received a case description outlining neurological signs in cattle, a digitized brain histology slide, and liver and brain tissue samples for optional chemistry analysis. Thirteen of 14 VDLs successfully diagnosed lead toxicosis by completing the following stages: (a) correctly identifying histological abnormalities, (b) providing three adequate differential diagnoses, (c) selecting adequate chemistry analyses to rule in or rule out possible causes, (d) accurately detecting lead concentration in the liver, and (e) interpreting the diagnostic significance of their results correctly. Importantly, participants first had to determine which chemistry analyses were appropriate and then to accurately quantify the target analytes. This approach provided greater confidence in the diagnostic capability of the laboratory by reducing the bias associated with being given a known chemical contaminant for which to test, typical of most chemistry PTs, and may therefore be of interest to PT providers and accreditation committees.

Proficiency test of SARS-CoV-2 Omicron variant detection in diagnostics samples by veterinary diagnostic laboratories

Veterinary diagnostic laboratories (VDLs) play a critical role in screening both human and animal samples for SARS-CoV-2. To evaluate the SARS-CoV-2 detection methods used by VDLs, a proficiency test was performed by the US Food and Drug Administration’s Veterinary Laboratory and Investigation and Response Network in collaboration with two other organizations. Thirty-two sets of 12 blind-coded samples were prepared by fortifying Molecular Transport Medium (MTM) or feline feces with SARS-CoV-2 Omicron variant or non-SARS-CoV-2 equine coronavirus RNA at various concentrations and shipped to 32 participants for blinded (unbiased) analysis. Results were analyzed according to the principles of International Organization for Standardization 16140-2:2016 using two approaches such as establishing the rate of detection (ROD) and the success rate by applying the analysis of binary outcome by logit approach. ROD provided the overall assessment of laboratories performance, whereas the novel logit approach provided an insight to more specific analysis based on the complexity of each sample. The ROD was 83% and 98% for MTM samples at 200 and 20000 genome copies per 100 µL, respectively. Fecal samples were classified as challenging exploratory, and results were not included in the assessment of performance but discussion purposes only. Fecal samples exhibited matrix interference impacting the performance. The ROD was 44% and 89% for fecal samples at 2000 and 20000 genome copies per 100 µL, respectively. The non-COVID coronavirus RNA, which was used to address the specificity, did not interfere with methods used. Establishing the success rate by evaluating the qualitative results (detected/not detected) applying a logit approach revealed that, out of thirty-two participants, twenty-eight had satisfactory results, one participant had unsatisfactory results, and three participants had questionable results for MTM samples. For fecal samples, three participants out of thirty-two did not meet the expectations at higher concentrations. Lower concentrations of fecal samples were excluded from this analysis. Again, the fecal samples were considered as challenge samples and the results were provided to assist participants in their continuous efforts to improve their performance and not to evaluate their performance.

Validation and interlaboratory comparison of anticoagulant rodenticide analysis in animal livers using ultra-performance liquid chromatography-mass spectrometry

Anticoagulant rodenticides (ARs) are used to control rodent populations. Poisoning of non-target species can occur by accidental consumption of commercial formulations used for rodent control. A robust method for determining ARs in animal tissues is important for animal postmortem diagnostic and forensic purposes. We evaluated an ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) method to quantify 8 ARs (brodifacoum, bromadiolone, chlorophacinone, coumachlor, dicoumarol, difethialone, diphacinone, warfarin) in a wide range of animal (bovine, canine, chicken, equine, porcine) liver samples, including incurred samples. We further evaluated UPLC-MS in 2 interlaboratory comparison (ILC) studies; one an ILC exercise (ICE), the other a proficiency test (PT). The limits of detection of UPLC-MS were 0.3-3.1 ng/g, and the limits of quantification were 0.8-9.4 ng/g. The recoveries obtained using UPLC-MS were 90-115%, and relative SDs were 1.2-13% for each of the 8 ARs for the 50, 500, and 2,000 ng/g spiked liver samples. The overall accuracy from the laboratories participating in the 2 ILC studies (4 and 11 laboratories for ICE and PT studies, respectively) were 86-118%, with relative repeatability SDs of 3.7-11%, relative reproducibility SDs of 7.8-31.2%, and Horwitz ratio values of 0.5-1.5. Via the ILC studies, we verified the accuracy of UPLC-MS for AR analysis in liver matrices and demonstrated that ILC can be utilized to evaluate performance characteristics of analytical methods.