Colouration by total internal reflection and interference at microscale concave interfaces.

Many physical phenomena create colour: spectrally selective light absorption by pigments and dyes1,2, material-specific optical dispersion3 and light interference4-11 in micrometre-scale and nanometre-scale periodic structures12-17. In addition, scattering, diffraction and interference mechanisms are inherent to spherical droplets18, which contribute to atmospheric phenomena such as glories, coronas and rainbows19. Here we describe a previously unrecognized mechanism for creating iridescent structural colour with large angular spectral separation. Light travelling along different trajectories of total internal reflection at a concave optical interface can interfere to generate brilliant patterns of colour. The effect is generated at interfaces with dimensions that are orders of magnitude larger than the wavelength of visible light and is readily observed in systems as simple as water drops condensed on a transparent substrate. We also exploit this phenomenon in complex systems, including multiphase droplets, three-dimensional patterned polymer surfaces and solid microparticles, to create patterns of iridescent colour that are consistent with theoretical predictions. Such controllable structural colouration is straightforward to generate at microscale interfaces, so we expect that the design principles and predictive theory outlined here will be of interest both for fundamental exploration in optics and for application in functional colloidal inks and paints, displays and sensors.

Temperature-Dependent Excitonic Light Manipulation with Atomically Thin Optical Elements.

Monolayer 2D semiconductors, such as WS2, exhibit uniquely strong light-matter interactions due to exciton resonances that enable atomically thin optical elements. Similar to geometry-dependent plasmon and Mie resonances, these intrinsic material resonances offer coherent and tunable light scattering. Thus far, the impact of the excitons' temporal dynamics on the performance of such excitonic metasurfaces remains unexplored. Here, we show how the excitonic decay rates dictate the focusing efficiency of an atomically thin lens carved directly out of exfoliated monolayer WS2. By isolating the coherent exciton radiation from the incoherent background in the focus of the lens, we obtain a direct measure of the role of exciton radiation in wavefront shaping. Furthermore, we investigate the influence of exciton-phonon scattering by characterizing the focusing efficiency as a function of temperature, demonstrating an increased optical efficiency at cryogenic temperatures. Our results provide valuable insights into the role of excitonic light scattering in 2D nanophotonic devices.

Direct Exfoliation of Nanoribbons from Bulk van der Waals Crystals.

Confinement of monolayers into quasi-1D atomically thin nanoribbons could lead to novel quantum phenomena beyond those achieved in their bulk and monolayer counterparts. However, current experimental availability of nanoribbon species beyond graphene is limited to bottom-up synthesis or lithographic patterning. In this study, a versatile and direct approach is introduced to exfoliate bulk van der Waals crystals as nanoribbons. Akin to the Scotch tape exfoliation method for producing monolayers, this technique provides convenient access to a wide range of nanoribbons derived from their corresponding bulk crystals, including MoS2, WS2, MoSe2, WSe2, MoTe2, WTe2, ReS2, and hBN. The nanoribbons are predominantly monolayer, single-crystalline, parallel-aligned, flat, and exhibit high aspect ratios. The role of confinement, strain, and edge configuration of these nanoribbons is observed in their electrical, magnetic, and optical properties. This versatile exfoliation technique provides a universal route for producing a variety of nanoribbon materials and supports the study of their fundamental properties and potential applications.

Anatomical classification of feline congenital extrahepatic portosystemic shunts based on CT angiography: A SVSTS and VIRIES multi-institutional study in 231 cats.

The prevalence of anatomical-based subtypes of feline congenital extrahepatic portosystemic shunts (EHPSS) has not been completely elucidated. The goal of this study was to use CT angiography to create an anatomical-based nomenclature system for feline congenital EHPSS. Additionally, subjective portal perfusion scores were generated to determine if intrinsic portal vein development was associated with different shunt conformations or patient age at the time of CT. The SVSTS and VIRIES list services were used to recruit cases. Data collected included patient DOB, gender, breed, weight, CT date, and reported diagnosis. Shunts were classified based upon (1) the shunt portal vessel(s) of origin, (2) the shunt systemic vessel(s) of insertion, and (3) any substantial portal vessels contributing to the shunt. Additionally, hepatic portal perfusion was subjectively scored between 1 (poor/none) and 5 (good/normal) based on the caliber of the intrahepatic PVs. A total of 264 CT scans were submitted from 29 institutions. Due to exclusion criteria, 33 (13%) were removed, leaving 231 CT scans to be included. Twenty-five different EHPSS anatomies were identified with five classifications accounting for 78% of all shunts (LGP [53%], LGC-post [11%], LCG [7%], LGC-pre [4%], and PC [4%]). Shunt origin involved the left gastric vein in 75% of the described classifications. Significant differences were identified among the five most common shunt types with respect to age at the time of CT scan (P = .002), breed (P < .001), and subjective portal perfusion score (P < .001). This refined anatomical classification system for feline EHPSS may enable improved understanding, treatment comparisons, and outcome prediction for cats with these anomalies.

Frequency Variation and Dose Modification of Benznidazole Administration for the Treatment of Trypanosoma cruzi Infection in Mice, Dogs, and Nonhuman Primates.

Trypanosoma cruzi naturally infects a broad range of mammalian species and frequently results in the pathology that has been most extensively characterized in human Chagas disease. Currently employed treatment regimens fail to achieve parasitological cure of T. cruzi infection in the majority of cases. In this study, we have extended our previous investigations of more effective, higher dose, intermittent administration protocols using the FDA-approved drug benznidazole (BNZ), in experimentally infected mice and in naturally infected dogs and nonhuman primates (NHP). Collectively, these studies demonstrate that twice-weekly administration of BNZ for more than 4 months at doses that are ~2.5-fold that of previously used daily dosing protocols, provided the best chance to obtain parasitological cure. Dosing less frequently or for shorter time periods was less dependable in all species. Prior treatment using an ineffective dosing regimen in NHPs did not prevent the attainment of parasitological cure with an intensified BNZ dosing protocol. Furthermore, parasites isolated after a failed BNZ treatment showed nearly identical susceptibility to BNZ as those obtained prior to treatment, confirming the low risk of induction of drug resistance with BNZ and the ability to adjust the treatment protocol when an initial regimen fails. These results provide guidance for the use of BNZ as an effective treatment for T. cruzi infection and encourage its wider use, minimally in high value dogs and at-risk NHP, but also potentially in humans, until better options are available.

Defining ruxolitinib failure and transition to next-line therapy for patients with myelofibrosis: a modified Delphi panel consensus study.

Aim: To define ruxolitinib failure and develop parameters to guide transition to next-line therapy for patients with myelofibrosis. Methods: A modified Delphi panel with 14 hematologists-oncologists. Survey concepts included defining primary refractory status, loss of response, disease progression, intolerance and transition to next-line therapy. Results: Ruxolitinib failure may be defined as no improvement in symptoms or spleen size, progressive disease or ruxolitinib intolerance, following a maximally tolerated dose for ≥3 months. Loss of spleen response 1 month after initial response may prompt discontinuation. Lack of evidence to inform transition to next-line therapy was noted; tapering ruxolitinib should be considered according to ruxolitinib dose and patient characteristics. Conclusion: Expert consensus was provided on defining ruxolitinib failure and transition to next-line therapy as summarized in this position paper, which may support considerations in the development of future clinical practice guidelines.

People with myelofibrosis who receive treatment with ruxolitinib may need to stop treatment because it is not working or they cannot tolerate the side effects. There is little good scientific information available about how and when to stop ruxolitinib treatment, and how to move to another treatment after stopping ruxolitinib. A group of clinical experts in hematology and oncology followed a scientific process, called the Delphi method, to discuss this topic and to reach agreement on the most important aspects of this challenge. The experts agreed that ruxolitinib failure may be defined as having no improvement in symptoms or spleen size, progressive disease or ruxolitinib intolerance, after the patient was receiving the highest dose they could tolerate for ≥3 months. The results of this expert discussion may support patients and their healthcare providers making decisions in real life, and development of future clinical practice guidelines.

The Use of a Modified Script Concordance Test in Clinical Rounds to Foster and Assess Clinical Reasoning Skills.

The development of clinical reasoning skills is a high priority during clinical service, but an unpredictable case load and limited time for formal instruction makes it challenging for faculty to foster and assess students' individual clinical reasoning skills. We developed an assessment for learning activity that helps students build their clinical reasoning skills based on a modified version of the script concordance test (SCT). To modify the standard SCT, we simplified it by limiting students to a 3-point Likert scale instead of a 5-point scale and added a free-text box for students to provide justification for their answer. Students completed the modified SCT during clinical rounds to prompt a group discussion with the instructor. Student feedback was positive, and the instructor gained valuable insight into the students' thought process. A modified SCT can be adopted as part of a multimodal approach to teaching on the clinic floor. The purpose of this article is to describe our modifications to the standard SCT and findings from implementation in a clinical rounds setting as a method of formative assessment for learning and developing clinical reasoning skills.

Correlations between age, body size, sex, and conformation and ultrasound-measured femoral vessel diameter in the dog, with implications for transvascular procedural planning.

Transvascular interventional radiology procedures have advanced in veterinary medicine, but basic knowledge about expected vascular size and vascular imaging requires further exploration. A prospective analytical study of 230 client-owned dogs was carried out to investigate correlations between ultrasound-measured femoral artery (FA) and femoral vein (FV) diameter and various morphometric and demographic dog variables, compare ultrasound-measured femoral vessel diameter to diameter predicted by body weight, compare right- and left-sided femoral vessel diameter, and assess measurement repeatability. Internal diameter of the FA and FV was measured with ultrasound bilaterally. Allometrically scaled body weight had the strongest correlation with FA and FV diameter (correlation coefficients: 0.92 and 0.80, respectively), although thigh circumference (FA: 0.89; FV:0.78) and withers height (FA: 0.84; FV: 0.76) were also strongly correlated. Within the entire population, males had a smaller FA (P = .005), but not FV (P = .278), than females and age was negatively associated with FA (P = .031) and FV (P < .001) diameter. Compared to ultrasound-derived measurements, body weight-predicted diameter overestimated by at least one French gauge in 32.6% and 35.2% of dogs for the FA and FV, respectively. Comparison of left and right FA and FV diameter revealed minimal mean differences, though limits of agreement could encompass multiple French gauge sizes: (Mean difference [limits of agreement]: FA = 0.00 mm [0.85-0.84 mm]; FV = 0.04 mm [1.92-1.99 mm]). Intra- and interoperator repeatability coefficients of variation were <9%. Femoral vessel diameter in dogs is influenced by multiple factors, with potential for clinically relevant differences between right- and left-sided vessels. Ultrasound measurement of femoral vessels could improve transvascular preprocedural planning.

The Creation of a Collaborative, Case-Based Learning Experience in a Large-Enrollment Classroom.

Numerous educational studies have shown that passive learning methods are frequently associated with disappointing learning outcomes, yet many faculty instructors continue to rely on passive didactic lectures. This article describes the creation of an active learning teaching approach-referred to as the collaborative, case-based classroom-that combines three pedagogical strategies: peer-assisted learning, case-based learning, and just-in-time teaching. Data from student surveys of a third-year cardiology elective showed a preference for this teaching approach compared with a case-based lecture. Six major themes emerged from survey analysis: engagement/interactivity, instructional benefit, clinical reasoning, clinical relevance, peer-assisted learning, and timely feedback. Although detailed here in the context of a cardiology elective, the collaborative, case-based classroom is a teaching approach that could be modified to fit a variety of other teaching environments.

Selected cardiac abnormalities in Trypanosoma cruzi serologically positive, discordant, and negative working dogs along the Texas-Mexico border.

BACKGROUND: Chagas disease is increasingly recognized in the southern U.S., where triatomine vectors transmit Trypanosoma cruzi among wildlife and domestic dogs with occasional vector spillover to humans. As in humans, clinical outcome in dogs is variable, ranging from acute death to asymptomatic infections or chronic heart disease. In order to characterize cardiac manifestations of T. cruzi infections, we tracked a cohort of naturally-infected dogs and a matched cohort of uninfected dogs. We hypothesized that selected measures of cardiac disease (abnormal rate, abnormal rhythm, and elevated cardiac troponin I (cTnI; a biomarker of cardiac injury)) would occur more commonly in infected than uninfected dogs matched by age, breed, sex and location. In addition to the clearly positive and negative dogs, we specifically tracked dogs with discordant test results across three independent serological assays to gather clinical data that might elucidate the infection status of these animals and inform the utility of the different testing approaches. RESULTS: We placed an ambulatory ECG monitor (Holter) on 48 government working dogs and analyzed 39 successful recordings that met length and quality criteria from 17 T. cruzi-infected, 18 uninfected dogs and 4 dogs with discordant results. Overall, 76.5% of positive, 100.0% of discordant, and 11.1% of negative dogs showed > 1 ECG abnormality (p < 0.0001), and positive and discordant dogs had a higher mean number of different types of ECG abnormalities than negative dogs (p < 0.001-0.014). The most common cardiac abnormalities included supraventricular and ventricular arrhythmias and atrioventricular block. Positive dogs had higher serum concentrations of cTnI than both negative dogs (p = 0.044) and discordant dogs (p = 0.06). Based on dog handler reports, nearly all (4/5; 80%) dogs with reported performance decline or fatigue were T. cruzi-infected dogs. CONCLUSIONS: Further understanding cardiac manifestations in dogs naturally infected with T. cruzi is critical for prognostication, establishing a baseline for drug and vaccine studies, and better understanding of zoonotic risk.

Electrocardiographic abnormalities are frequently detected in healthy adult Borzoi with a normal echocardiogram.

OBJECTIVE: Borzoi reportedly experience sudden death. The objective of this study was to report ECG intervals, amplitudes, and frequency of ECG abnormalities in clinically healthy Borzoi. METHODS: 98 clinically healthy Borzoi were prospectively recruited and underwent echocardiogram, ECG, and cardiac troponin I testing between October 2020 and December 2022. Standard ECG measurements were obtained. Early repolarization notches and slurs were recorded. RESULTS: Of 82 Borzoi with a structurally normal echocardiogram, ventricular arrhythmias were documented in 8 (10%) dogs, all of which had normal cardiac troponin I concentrations. Median P wave duration was 55 milliseconds (range, 45 to 70 milliseconds). Median PR interval was 125 milliseconds (range, 80 to 175 milliseconds). Thirty-one (38%) Borzoi had first-degree atrioventricular block (PR interval > 130 milliseconds). Median QRS duration was 65 milliseconds (range, 48 to 90 milliseconds). Median QT interval was 235 milliseconds (range, 185 to 275 milliseconds). Twenty-nine (35%) and 15 (18%) of 82 Borzoi had QT intervals > 240 or > 250 milliseconds, respectively. Sixty-seven of 82 (82%) Borzoi had early repolarization notches or slurs. Seventeen of 82 (21%) Borzoi had an abnormality of the ST segment, most commonly convexity/doming. Convexity of the ST segment was intermittent (n = 9) or persistent (4). CONCLUSIONS: Ventricular arrhythmias, early repolarization, prolonged QT intervals, and ST segment abnormalities are not infrequent in clinically healthy Borzoi. P, PR, and QRS durations are commonly prolonged compared to general canine reference intervals. CLINICAL RELEVANCE: Future study into heritable channelopathies in Borzoi is warranted given the frequency of ventricular arrhythmias, repolarization abnormalities, and sudden death in the breed. Breed-specific ECG reference intervals are needed.

Echocardiographic values and prevalence of cardiac abnormalities in clinically healthy adult Borzoi dogs.

OBJECTIVE: To develop breed-specific echocardiographic values for normal Borzoi and to report the prevalence of structural cardiac abnormalities. ANIMALS: 146 clinically healthy, adult Borzoi dogs. METHODS: Cardiac auscultation and standard echocardiograms were performed. Longitudinal follow-up was described in a subset of dogs (n = 25). RESULTS: Most Borzoi were structurally normal (119/146, 81.5%), with breed-specific echocardiographic values generated independently for each sex, as females weighed significantly less than males (30.4 ± 3.8 kg vs 38.3 ± 4.1 kg, respectively; P < .001), and a significant impact of sex was found on most measurements. Physiologic heart murmurs were identified in 64/119 (53.8%) normal dogs. Thirty-six (30.2%) structurally normal dogs had trace or mild mitral regurgitation, and 43 (36.1%) had trace or mild tricuspid regurgitation. Structural cardiac disease was identified in 21 dogs (14.4%), including 9 dogs (6.2%) with dilated cardiomyopathy (DCM), 9 dogs (6.2%) with stage B1 myxomatous mitral valve disease (MMVD), and 3 (2.1%) dogs with congenital abnormalities. Seven dogs (4.8%) had equivocal abnormalities. During follow-up, new dogs were diagnosed with occult DCM (n = 3), equivocal DCM (1), and stage B1 MMVD (2). Two dogs originally diagnosed with DCM (1 occult and 1 equivocal) normalized after diet change. CLINICAL RELEVANCE: Borzoi dogs commonly have physiologic heart murmurs and mild atrioventricular valve regurgitation. Both DCM and MMVD were identified at similar frequencies in healthy Borzoi, although dogs with MMVD all had normal heart sizes. Echocardiographic screening for DCM in Borzoi should be considered, with breed-specific echocardiographic values now available for improved diagnostic confidence.

Clinical characteristics, treatment patterns, and outcomes among African American and White patients with multiple myeloma in the United States.

Multiple myeloma (MM) is more common among Black/African American (AA) patients than White patients, but survival rate improvements are less pronounced for AA patients. This study evaluated treatment patterns and survival among 1810 AA and 5904 White adults in the United States with ≥1 MM treatment and ≥3 months of follow-up. Median time from diagnosis to systemic treatment was longer (37 [0-3053] vs. 35 [0-3664] days) and median time to stem cell transplant (SCT) was longer for AA than White patients (255 [1-2352] vs. 225 [1-3094] days), and AA patients were less likely to receive SCT (odds ratio [OR]: 0.66; 95% confidence interval [CI]: 0.58-0.76). Despite disparities in treatment between AA and White patients, AA patients demonstrated lower risk of death (OR: 0.89; 95% CI: 0.81-0.96). These data highlight the value of equal access to care for the improvement of health outcomes in underserved populations.

Positive clinical outcome using a modified dosing regimen of benznidazole in dogs at high risk for infection or acutely infected with Trypanosoma cruzi.

Trypanosoma cruzi infection in dogs can cause heart failure and sudden death with few treatment options available. A litter of 4 dogs living in a T cruzi endemic area were randomized to prophylaxis and nonprophylaxis groups as part of a study evaluating a modified benznidazole dosing regimen administered twice weekly to prevent T cruzi infection during a vector transmission season. The 2 dogs that received prophylaxis remained healthy without T cruzi infection or cardiac disease for >2 years. One dog that did not receive prophylaxis died unexpectedly with acute T cruzi-induced pancarditis, and the second dog tested positive for T cruzi and developed complex arrhythmias with markedly increased cardiac troponin I and improved with a higher benznidazole treatment dose. Although the small sample size precludes definitive conclusions, we describe the potential clinical benefit of prophylactic and early treatment with modified benznidazole dosing regimens for dogs with T cruzi infection.

Electrocardiographic abnormalities are associated with seropositive Trypanosoma cruzi infection status using a simplified cardiac diagnostic evaluation in dogs.

OBJECTIVE: To describe associations between cardiac abnormalities and Trypanosoma cruzi serostatus by use of a simplified diagnostic evaluation in dogs at risk for T cruzi infection. METHODS: A prospective, cross-sectional study was performed using a simplified diagnostic evaluation including high-sensitivity cardiac troponin I, 30-second ECG, and echocardiogram with 7 variables in 46 client-owned dogs from high-risk environments. Dogs were categorized as serologically positive (SP), negative (SN), or discordant (SD) by use of 2 antibody tests. Functional evaluation of cardiac health scores and blood PCR were obtained. RESULTS: Dogs were SP (n = 19), SN (17), and SD (10), with 9 PCR positive (7 SP, 1 SN, 1 SD). Troponin was above reference range in 6 of 46 (4 SP, 1 SN, 1 SD), and functional evaluation of cardiac health scores were 0 in all dogs. Conduction system abnormalities (prolonged interval durations, second-degree atrioventricular block, splintered QRS complex) and ventricular arrhythmias were documented in 8 (7 SP, 0 SN, 1 SD). Twenty-six (12 SP, 8 SN, 6 SD) had echocardiographic abnormalities, most often myxomatous mitral valve disease (MMVD) and left ventricular enlargement. Seropositive dogs were significantly older and had a higher likelihood of MMVD. Conduction system abnormalities were associated with positive serostatus. CONCLUSIONS: Echocardiographic abnormalities were complicated by MMVD and did not distinguish between serostatus. An ECG with assessment and detailed measurement of complexes and cardiac troponin I are simple tests to perform with abnormalities detected in seroreactive dogs. CLINICAL RELEVANCE: Electrocardiographic abnormalities in high-risk or seroreactive dogs should prompt further evaluation and monitoring of T cruzi infection.

Hidden phonon highways promote photoinduced interlayer energy transfer in twisted transition metal dichalcogenide heterostructures.

Vertically stacked van der Waals (vdW) heterostructures exhibit unique electronic, optical, and thermal properties that can be manipulated by twist-angle engineering. However, the weak phononic coupling at a bilayer interface imposes a fundamental thermal bottleneck for future two-dimensional devices. Using ultrafast electron diffraction, we directly investigated photoinduced nonequilibrium phonon dynamics in MoS2/WS2 at 4° twist angle and WSe2/MoSe2 heterobilayers with twist angles of 7°, 16°, and 25°. We identified an interlayer heat transfer channel with a characteristic timescale of ~20 picoseconds, about one order of magnitude faster than molecular dynamics simulations assuming initial intralayer thermalization. Atomistic calculations involving phonon-phonon scattering suggest that this process originates from the nonthermal phonon population following the initial interlayer charge transfer and scattering. Our findings present an avenue for thermal management in vdW heterostructures by tailoring nonequilibrium phonon populations.

An intrapericardial technique for PDA ligation: surgical description and clinical outcome in 35 dogs.

A number of surgical techniques have been reported for dissection and ligation of patent ductus arteriosi (PDAs) in dogs. The objectives of this study were to provide a detailed description of an intrapericardial technique for PDA dissection and ligation and to report the clinical outcome of that technique in dogs. Medical records of 35 dogs were retrospectively reviewed for signalment, clinical signs, echocardiographic findings, surgical time, intra- and postoperative complications, and completeness of ductal closure. Median surgery time was 60 min (range, 35-125 min). Neither intraoperative nor postoperative complications occurred. Within 48 hr of surgery, the continuous left basilar heart murmur was absent in all dogs, and complete echocardiographic closure was confirmed in 29 of 32 dogs. Residual flow was identified echocardiographically in three dogs within 48 hr of surgery. Residual flow was decreased in one dog at 1 mo, which resolved within 33 mo. One dog had mild residual flow postoperatively but did not return for follow-up. The intrapericardial technique was successful for PDA dissection and ligation and had a lower rate (6%) of echocardiographic residual flow compared with previously reported techniques.

Palatal erosion and oronasal fistulation following covered nasopharyngeal stent placement in two dogs.

Treatment options for dogs with nasopharyngeal stenosis include fluoroscopic placement of metallic stents. Reported complications include entrapment of hair and food, obstruction and persistent nasal discharge. Two toy breed dogs were examined for persistent nasal discharge and halitosis at 4 and 20 months after placement of permanent metallic stents for acquired nasopharyngeal stenosis. Full thickness defects were found in the palate of both dogs, with extensive communication between the mouth and the nasal passages. Portions of the metal stent were observed within the lesion in both patients. Additional treatment was declined by the owner of one dog; the stent was removed through the fistula in the other dog. Palatal erosion with secondary oronasal fistulation is a potential complication of nasopharyngeal stent placement in dogs.

Analytical validation, sample stability, and clinical evaluation of a new high-sensitivity cardiac troponin I immunoassay for use in dogs, with comparison to a previous ultrasensitive assay.

Cardiac troponin I (cTnI) is considered the gold standard biomarker for myocardial injury and shows a high degree of homology between humans and dogs. The ADVIA Centaur XP High-Sensitivity Troponin I (AC-cTnI-HS) assay has been validated for use in humans but not dogs. The study objectives were to analytically validate the AC-cTnI-HS assay in dogs, to assess correlation between the AC-cTnI-HS and a previous ADVIA Centaur TnI-Ultra (AC-cTnI-U) assay, to assess cTnI sample storage stability, and to clinically evaluate the AC-cTnI-HS assay in healthy dogs and dogs with cardiac disease. Canine serum samples were used for analytical validation. Intra- and inter-assay variability, dilutional parallelism, and spiking recovery were assessed. Samples from 196 client-owned dogs were evaluated (healthy dogs (n = 39) or dogs with congenital heart disease (n = 54), myxomatous mitral valve disease (n = 68), dilated cardiomyopathy (n = 15), or myocarditis (n = 20)). Inter- and intra-assay coefficient of variation (%CV) was between 2.8-41.4% and 3.8-30.2%, respectively, with pools with concentrations >20 pg/mL all having %CVs <10%. The observed to expected ratios for dilutional parallelism and spiking recovery experiments ranged between 92.3 and 266.7.0% and 84.3 and 108%, respectively. A strong correlation between the AC-cTnI-HS and AC-cTnI-U assays was observed (Spearman's ρ = 0.927), though a proportional bias existed, with AC-cTnI-HS assay concentrations being proportionally lower than AC-cTnI-U assay concentrations. Serum samples stored at -80°C had stable cTnI measurements for up to 2.7 years and after a single freeze-thaw cycle. Healthy dogs and dogs with congenital heart disease had significantly lower cTnI concentrations than dogs in the other three groups. The AC-cTnI-HS assay precisely, reproducibly, and accurately measures cTnI concentrations in dog serum with cTnI concentrations >20 pg/mL.

Validation of a multiplex microsphere immunoassay for detection of antibodies to Trypanosoma cruzi in dogs.

The vector-borne protozoan parasite Trypanosoma cruzi causes Chagas disease in humans, dogs, and many other mammalian hosts. Canine Chagas disease is increasingly diagnosed in dogs of the southern United States where triatomine insect vectors occur, and there are limited veterinary testing options; only the indirect fluorescent antibody (IFA) test is offered at a single accredited diagnostic laboratory. We evaluated a multiplex microsphere immunoassay (MIA) for the detection of antibodies against T. cruzi in dogs and compared it with existing serologic methods to establish cutoff values and relative sensitivity and specificity. We tested 135 canine sera that had been characterized using the IFA and off-label use of 2 commercial rapid assays with our multiplex MIA against 12 antigens: 9 T. cruzi antigens, a negative control recombinant protein (green fluorescent protein, GFP), a Leishmania antigen, and a canine parvovirus antigen (used as an antibody control given near-ubiquitous parvoviral vaccination). The median fluorescence intensity (MFI) ratio between each T. cruzi antigen and GFP was calculated for every sample. Samples with an antigen:GFP MFI ratio > 4 SDs above the mean of 25 known-negative sera were considered positive to that antigen. Samples testing positive to ≥ 2 antigens were considered positive for T. cruzi antibodies. Compared to the IFA, our multiplex MIA had a relative sensitivity of 100% and specificity of 97.0%. Given its precision, high-throughput format, potential for automation, and lack of subjective interpretation, our multiplex MIA should be considered a valid and improved assay for T. cruzi antibodies in dogs.