Use of heterologous immunoassays for quantification of serum proteins: The case of canine C-reactive protein

Analytical validation of an automated assay to measure calprotectin (S100A8/A9) in dog saliva and serum and changes in canine leishmaniasis, pyometra and hyperadrenocorticism

BACKGROUND

Calprotectin (S100A8/A9) is a protein related to innate immunity that is considered a biomarker of inflammation. Currently, there is a commercially available automated assay for the measurement of calprotectin concentration (Bühlmann fCal Turbo® assay), which has been previously validated for saliva and serum of swine and for saliva of horses, and in the canine species it has been validated for use with fecal samples, but it has not been previously validated in canine saliva or serum. Thus, the aim of this study was to perform an analytical validation of an automated assay for the measurement of calprotectin in the saliva and serum of dogs. In addition, changes in this protein in saliva and serum of three diseases with different pathogenic mechanisms - leishmaniasis, pyometra and hyperadrenocorticism - were evaluated. Finally, in these diseases, the correlation of salivary and serum calprotectin with the serum levels of three acute phase proteins (APPs), including C-reactive protein (CRP), haptoglobin (Hp) and ferritin, was also assessed.

RESULTS

The analytical validation results showed that the assay was precise (coefficients of variation < 15% in all cases), accurate (the dilutional parallelism for serum and salivary calprotectin showed observed-to-expected ratios with a mean of 96.9% and 97.2%, respectively), and presented a limit of detection of 0.038 mg/L. When this assay was applied to the different diseases, a significant increase in the concentration of salivary calprotectin in dogs with leishmaniasis (p = 0.0002) and in those with pyometra (p = 0.002), compared to healthy ones, was observed, whereas no significant differences were found in serum. Furthermore, a significant positive moderate correlation was obtained between salivary calprotectin and serum CRP (r = 0.5; p = 0.001) and haptoglobin (r = 0.5; p = 0.002), and between calprotectin and CRP (r = 0.67; p < 0.001) in serum.

CONCLUSIONS

Calprotectin (S100A8/A9) can be measured in dog saliva and serum samples by the automated method validated in this study, and when measured in saliva it could be used as a potential biomarker of inflammation and immune activation in the dog.

Age-Related Changes in Gut Health and Behavioral Biomarkers in a Beagle Dog Population

The gut and the gut microbiome communicate with the nervous system through the gut-brain axis via neuroimmune and neuroendocrine mechanisms. Despite existing research, studies exploring this link in aging dogs are limited. This study aims to examine multiple blood and fecal biomarkers of intestinal health, along with various behavioral indicators based on saliva, blood, observations, and activity, in different age populations (junior: <2 y.o.; adult: 2-7 y.o.; senior: >7 y.o.) of thirty-seven Beagle dogs. In our study, Bacteroides were significantly higher in senior dogs. The relative abundance of Faecalibacterium and Blautia showed age-related trends, higher in senior and junior dogs, respectively. Fecal short-chain fatty acid concentration, especially acetate, increased with age, while propionate was higher in junior dogs. For the behavioral indicators we considered, blood thyroxine concentration, playing, exploring, and total activity were higher in junior dogs. The differences observed between the biomarkers of gut health and behavior, particularly those significant for the age correlations, emphasize the importance of considering age-related factors when studying the gut microbiome and behavior. However, further research is needed to better understand the mechanisms and specific pathways involved in the relationship between the studied biomarkers and age.

Changes in Biomarkers of Inflammation and Oxidative Status in Dogs Subjected to Celiotomy or Video-Assisted Ovariohysterectomy

We evaluated the surgical stress response of dogs undergoing three ovariohysterectomy (OVH) techniques. Twenty-nine healthy females were allocated into groups: celiotomy and ligature (CelioSut), celiotomy and bipolar energy (CelioBip), and a video-assisted technique using two portals and bipolar energy (VidBip). Clinical evaluation was performed, and the following blood analyses were determined: acute phase proteins (C-reactive protein and haptoglobin), white blood cell counting (WBC), and biomarkers of oxidative status. The VidBip required more time despite a smaller incision, lower heart rate, and earlier feeding and urination. All groups had high white blood cells counts; the C-reactive protein (CRP) levels peaked at 6 and 12 h in all groups and was higher in the CelioBip and VidBip groups compared to CelioSut; haptoglobin concentrations peaked at 48 h in all groups and increased in dogs of the CelioSut group. Trolox equivalent antioxidant capacity, ferric reducing ability of plasma, cupric reducing antioxidant capacity, and advanced oxidation protein were not significantly different among the groups or time points. Total thiol concentrations were lower in CelioBip and CelioSut groups. All surgical techniques induced an inflammatory and oxidative stress response, but the video-assisted technique produced early clinical recovery. The bipolar device produces fewer disturbances than suspensory ligament rupture and ligature.

Changes in Immunoglobulins G and A in the Saliva and Serum of Horses with Equine Gastric Ulcer Syndrome (EGUS) and Their Relationship with Other Immune and Redox Status Biomarkers

Equine Gastric Ulcer Syndrome (EGUS) is a widespread disease with a very high prevalence and importance in horses. It includes two conditions: Equine squamous gastric disease (ESGD), linked to acid disturbances, and Equine Glandular Gastric Disease (EGGD), associated with inflammation and immune system issues. In saliva, increased levels of immunological markers have been observed in this disease, indicating immune system involvement. In addition, changes in biomarkers of oxidative stress have been described. In horses, IgG and IgA are proteins that appear in saliva and serum and are considered to be the major proteins in specific immunity; however, their levels in horses with EGUS have not been previously studied. This report aims to evaluate IgG and IgA concentrations in the saliva and serum of horses with EGUS, measured by automated assays, and compare them with other biomarkers of the immune and oxidative stress system. This work validated the IgG and IgA assays in saliva and showed that IgA significantly increased in the saliva of horses with EGUS. When the correlation between IgG and IgA and other biomarkers of immune system issues and oxidative stress such as ADA, S100 A8-A9 (calprotectin), S100 A12 (calgranulin), uric acid, FRAS, and AOPP was studied, IgA in saliva showed a significant moderate correlation with adenosine deaminase, indicating its possible involvement in the immune reaction occurring in EGUS.

β-glucans from Euglena gracilis or Saccharomyces cerevisiae effects on immunity and inflammatory parameters in dogs

Considering the differences in molecular structure and function, the effects of β-1,3-glucans from Euglena gracilis and β-1,3/1,6-glucans from Saccharomyces cerevisiae on immune and inflammatory activities in dogs were compared. Four diets were compared: control without β-glucans (CON), 0.15 mg/kg BW/day of β-1,3/1,6-glucans (Β-Y15), 0.15 mg/kg BW/day of β-1,3-glucans (Β-S15), and 0.30 mg/kg BW/day of β-1,3-glucans (Β-S30). Thirty-two healthy dogs (eight per diet) were organized in a block design. All animals were fed CON for a 42-day washout period and then sorted into one of four diets for 42 days. Blood and faeces were collected at the beginning and end of the food intake period and analysed for serum and faecal cytokines, ex vivo production of hydrogen peroxide (H2O2) and nitric oxide (NO), phagocytic activity of neutrophils and monocytes, C-reactive protein (CRP), ex vivo production of IgG, and faecal concentrations of IgA and calprotectin. Data were evaluated using analysis of covariance and compared using Tukey's test (P<0.05). Dogs fed Β-Y15 showed higher serum IL-2 than dogs fed Β-S30 (P<0.05). A higher phagocytic index of monocytes was observed in dogs fed the B-S15 diet than in those fed the other diets, and a higher neutrophil phagocytic index was observed for B-S15 and B-Y15 than in dogs fed the CON diet (P<0.05). Monocytes from dogs fed B-S15 and B-S30 produced more NO and less H2O2 than those from the CON and B-Y15 groups (P<0.05). Despite in the reference value, CRP levels were higher in dogs fed B-S15 and B-S30 diets (P<0.05). β-1,3/1,6-glucan showed cell-mediated activation of the immune system, with increased serum IL-2 and neutrophil phagocytic index, whereas β-1,3-glucan acted on the immune system by increasing the ex vivo production of NO by monocytes, neutrophil phagocytic index, and serum CRP. Calprotectin and CRP levels did not support inflammation or other health issues related to β-glucan intake. In conclusion, both β-glucan sources modulated some immune and inflammatory parameters in dogs, however, different pathways have been suggested for the recognition and action of these molecules, reinforcing the necessity for further mechanistic studies, especially for E. gracilis β-1,3-glucan.

Divergences between serum C-reactive protein and ferritin concentrations in canine pyometra

The main aim of this report was to investigate and compare the response of serum C-reactive protein (CRP) and ferritin, two positive acute phase proteins (APPs) which usually show an increase in inflammatory processes, in dogs with pyometra. For this purpose, two different studies were made. In the first one , both proteins were measured together in an APPs profile in 25 dogs with pyometra, 25 dogs with pancreatitis (as an example of a positive inflammatory control group), and in 25 healthy dogs. In the second study, to advance the knowledge of the changes and evolution of serum ferritin and CRP in dogs with pyometra after treatment, the concentrations of both APPs were analyzed in 30 dogs with pyometra at diagnosis and after ovariohysterectomy and in 10 clinically healthy female dogs before and after elective spaying. In both studies, bitches with pyometra showed significant increases in serum CRP, indicating an inflammatory condition, but not in serum ferritin despite being a moderate positive APP. This divergence between the dynamics of these APPs could be a useful tool for the suspicion of cases of canine pyometra.

S-100 Proteins: Basics and Applications as Biomarkers in Animals with Special Focus on Calgranulins (S100A8, A9, and A12)

S100 proteins are a group of calcium-binding proteins which received this name because of their solubility in a 100% saturated solution of ammonium sulphate. They have a similar molecular mass of 10-12 KDa and share 25-65% similarity in their amino acid sequence. They are expressed in many tissues, and to date 25 different types of S100 proteins have been identified. This review aims to provide updated information about S100 proteins and their use as biomarkers in veterinary science, with special emphasis on the family of calgranulins that includes S100A8 (calgranulin A; myeloid-related protein 8, MRP8), S100A9 (calgranulin B; MRP14), and S100A12 (calgranulin C). The proteins SA100A8 and S100A9 can be linked, forming a heterodimer which is known as calprotectin. Calgranulins are related to the activation of inflammation and the immune system and increase in gastrointestinal diseases, inflammation and sepsis, immunomediated diseases, and obesity and endocrine disorders in different animal species. This review reflects the current knowledge about calgranulins in veterinary science, which should increase in the future to clarify their role in different diseases and potential as biomarkers and therapeutic targets, as well as the practical use of their measurement in non-invasive samples such as saliva or feces.

Acute Phase Proteins in Dogs with Natural Infection by Trypanosoma cruzi

Acute phase proteins have been used as tools for the diagnosis, monitoring, and prognosis of several diseases in domestic animals. However, the dynamics of these proteins in infection by Trypanosoma cruzi, the causative agent of Chagas disease in dogs, is still unknown. The aim of this study was to determine concentrations of acute phase proteins (C-reactive protein, haptoglobin, ferritin and paraoxonase-1) in dogs in a coastal town of Ecuador, with natural Trypanosoma cruzi infection with or without seroreactivity of Ehrlichia canis, Ehrlichia ewingii, Anaplasma phagocytophilum, Anaplasma platys, Borrelia burgdorferi and Dirofilaria immitis. For the detection of Trypanosoma cruzi serum antibodies, two different antigen-based enzyme-linked immunosorbent assay tests were implemented. For the detection of seroreactivity of Ehrlichia canis, Ehrlichia ewingii, Anaplasma phagocytophilum, Anaplasma platys, Borrelia burgdorferi and Dirofilaria immitis, an IDEXX SNAP^® 4Dx^® test was used. To determine the concentration of C-reactive protein and ferritin, an immunoturbidimetric assay was used; haptoglobin concentration was measured using a commercial colorimetric method validated in dogs; a spectrophotometric method was used to determine the serum concentration of paraoxonase-1. Results showed a reduction in the serum levels of paraoxonase-1 in Trypanosoma cruzi-seroreactive dogs, either with or without seroreactivity to other vector-borne diseases. A serum ferritin increment was observed in Trypanosoma cruzi-seroreactive dogs with seroreactivity to any other vector-borne diseases. Our findings suggest that paraoxonase-1 levels are reduced in Trypanosoma cruzi-seroreactive dogs without evident clinical signs of Chagas disease, despite their seroreactivity to the other vector-borne diseases studied. These findings could indicate an oxidative stress response in Trypanosoma cruzi-seroreactive dogs with no evident signs of inflammation.

Changes in Calprotectin (S100A8-A9) and Aldolase in the Saliva of Horses with Equine Gastric Ulcer Syndrome

Equine gastric ulcer syndrome (EGUS) is a highly prevalent disease that affects horses worldwide. Within EGUS, two different forms have been described: equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD). The associated clinical signs cause detrimental activity performance, reducing the quality of life of animals. Saliva can contain biomarkers for EGUS that could be potentially used as a complementary tool for diagnosis. The objective of this work was to evaluate the measurements of calprotectin (CALP) and aldolase in the saliva of horses as potential biomarkers of EGUS. For this purpose, automated assays for the quantification of these two proteins were analytically validated and applied for detecting EGUS in a total of 131 horses divided into 5 groups: healthy horses, ESGD, EGGD, combined ESGD and EGGD, and horses with other intestinal pathologies. The assays showed good precision and accuracy in analytical validation, and they were able to discriminate between horses with EGUS and healthy horses, especially in the case of CALP, although they did not show significant differences between horses with EGUS and horses with other diseases. In conclusion, salivary CALP and aldolase can be determined in the saliva of horses and further studies are warranted to elucidate the potential of these analytes as biomarkers in EGUS.

Measurement of Calprotectin (S100A8/A9) in the Saliva of Pigs: Validation Data of A Commercially Available Automated Assay and Changes in Sepsis, Inflammation, and Stress

Calprotectin (CALP, S100A8/A9), also named myeloid-related protein 8/14, is a dimer complex of S100A8 and S100A9 that belongs to the S-100 protein family. It is involved in inflammation and has a wide range of proinflammatory functions, such as cytokine production and regulation of leukocyte adhesion, migration, and phagocytosis. In humans, CALP traditionally can be measured in faeces, serum, and saliva as a biomarker of inflammation and sepsis. The objective of this study was to validate an automated assay for CALP measurements in the saliva of pigs, having the advantage of the use of a non-invasive sample that is easy to collect. The assay was precise and accurate. CALP in saliva measured by this assay showed significant changes depending on the hour of the day. It also showed significant increases in the saliva of pigs after the administration of lipopolysaccharide (LPS), and showed a rise, although with increases of lower magnitude, after a stressful stimulus. Further studies should be made to gain knowledge about the possible practical applications of the measurements of CALP in the saliva of pigs as a biomarker to evaluate the animals’ health and welfare.

Hepatosplenic lymphoma and visceral mast cell tumor in the liver of a dog with synchronous and multiple primary tumors

An 11-year-old spayed female American Cocker Spaniel was presented with a 4-week history of anorexia and a 1-week history of abdominal distension. Clinicopathologic and imaging abnormalities included intra-abdominal hemorrhage, granular lymphocytes (GLs) in abdominal fluid smears, a splenic mass, and hepatomegaly with diffuse multiple hypoechogenic nodules. Based on the cytologic, histologic, and immunohistochemical evaluation of the spleen and liver, the diagnosis was hepatosplenic T-cell lymphoma (HSTCL) of GLs. Postoperatively, the dog was maintained in good condition with chemotherapy (ACNU [nimustine], L-asparaginase, and prednisolone). However, on day 85, ultrasound-guided fine-needle aspiration of the liver revealed a proliferation in neoplastic mast cells not associated with the GLs. The dog was diagnosed with a visceral mast cell tumor (MCT) originating from the liver. The chemotherapy was switched to vinblastine and toceranib. The dog remained in good condition until day 141 but died due to the progression of MCT on day 158. Liver cytology on day 155 showed no GLs, although HSTCL is thought to be resistant to chemotherapy. After the definitive diagnosis of HSTCL, we monitored this patient's response to chemotherapy with blood tests, including complete blood counts, ultrasound imaging, and cytologic aspirates of liver. Although canine HSTCL has a poor prognosis, the possibility of a new neoplasm, including visceral MCT, should be considered. Periodic liver cytology might be worthwhile in dogs receiving chemotherapy for HSTCL.

Evaluation of the Randox and Fuji Dri-Chem vcCRP-P assays of canine C-reactive protein

In veterinary medicine, measurement of canine C-reactive protein (cCRP) is used widely to detect inflammatory diseases. We evaluated the precision of Randox and Fuji assays for cCRP, as well as accuracy, correlation, and agreement compared to a reference ELISA. Blood samples from 71 client-owned dogs (20 healthy, 51 diseased) were analyzed with the 3 assays. Inter-assay CVs were ~3.5% with both the Randox and Fuji assays. The mean biases were −1.90% for the Randox and −5.93% for the Fuji test; the targeted biases were ~8.5% for both assays. The CV, bias, and observed total error were acceptable for the 2 assays compared to ASVCP recommendations based on biological variation studies. The Spearman correlation coefficient for cCRP concentration compared with the reference ELISA was 0.83 for the Randox test and 0.92 for the Fuji test. Both assays measured cCRP precisely at intermediate and increased concentrations. Correlation with the reference ELISA was good, and both assays could be used to evaluate cCRP concentrations in veterinary practice. However, the assays did not reach analytical agreement; hence the results obtained by these assays are not interchangeable, and serial monitoring of cCRP requires the use of the same assay.

Measurement of procalcitonin in saliva of pigs: a pilot study

Background

Procalcitonin (PCT) is a widely used biomarker of sepsis in human medicine and can have potential applications in the veterinary field. This study aimed to explore whether PCT could be measured in the saliva of pigs and whether its concentration changes in sepsis. Therefore, a specific assay was developed and analytically validated, and changes in PCT concentration were evaluated in two conditions: a) in an experimental model of sepsis produced by the administration of lipopolysaccharide (LPS) to pigs (n = 5), that was compared with a model of non-septic inflammation induced by turpentine oil (n = 4), and b) in healthy piglets (n = 11) compared to piglets with meningitis (n = 20), a disease that usually involves sepsis and whose treatment often requires large amounts of antibiotics in farms.

Results

The assay showed coefficients of variation within the recommended limits and adequate linearity after serial sample dilutions. The method's detection limit was set at 68 μg/L, and the lower limit of quantification was 414 μg/L. In the LPS experiment, higher concentrations of PCT were found after 24 h in the animals injected with LPS (mean = 5790 μg/L) compared to those treated with turpentine oil (mean = 2127 μg/L, P = 0.045). Also, animals with meningitis had higher concentrations of PCT (mean = 21515 μg/L) than healthy pigs (mean = 6096 μg/L, P value < 0.0001).

Conclusions

According to these results, this assay could be potentially used as a tool for the non-invasive detection of sepsis in pigs, which is currently a topic of high importance due to antibiotic use restriction.

Measurement and clinical applications of C-reactive protein in gastrointestinal diseases of dogs

C-reactive protein (CRP) is a positive acute-phase protein, serum concentrations of which increase nonspecifically in response to inflammatory processes of the dog. As such, it can aid in the identification of inflammatory disease and, maybe more importantly, the objective monitoring of disease progression. In dogs, CRP is frequently used to evaluate dogs with gastrointestinal diseases, such as chronic inflammatory enteropathies (also termed idiopathic inflammatory bowel disease), acute pancreatitis, canine parvovirus infection, hepatic disease, acute abdomen, and protein-losing enteropathy. The diversity of the assays available to measure CRP in dogs is nearly as numerous as the diseases in which serum concentrations of this protein are increased. Assay methodologies include laser nephelometric immunoassays, enzyme-linked immunosorbent assays, immunoturbidimetric assays, and time-resolved immunofluorometric assays. While many of these assays are acceptable for clinical use in the dog, the same assay and analyzer should be used to measure a patient's CRP concentration longitudinally. By looking at the uses of CRP in human gastroenterology, including reducing the duration of antibiotic therapy, the veterinary profession can gain insight into novel ways in which serum CRP concentration measurements might be applied in veterinary medicine in the future.

Preoperative serum C-reactive protein concentration can be used to detect gallbladder rupture in dogs with gallbladder mucocele

OBJECTIVE

To determine whether serum C-reactive protein (CRP) concentration could be used to detect gallbladder rupture (GBR) prior to surgery in dogs undergoing cholecystectomy for treatment of gallbladder mucocele (GBM).

ANIMALS

45 dogs that underwent cholecystectomy because of GBM at a companion animal referral hospital from 2017 to 2020.

PROCEDURES

Electronic medical records were reviewed, and dogs were included if serum CRP concentration had been measured within 24 hours prior to cholecystectomy. Dogs were grouped as to whether the gallbladder was found to be ruptured or intact during surgery. Accuracy of using preoperative CRP concentration to predict GBR was compared with accuracy of abdominal ultrasonography and other preoperative blood tests.

RESULTS

GBR was present in 15 dogs at the time of surgery. Median preoperative CRP concentration was significantly higher in dogs with GBR (15.1 mg/dL; interquartile range, 7.4 to 16.8 mg/dL) than in dogs with an intact gallbladder (2.65 mg/dL; interquartile range, 0.97 to 13.4 mg/dL). Sensitivity, specificity, and accuracy of using preoperative CRP concentration to predict GBR were 100%, 67%, and 78%, respectively.

CLINICAL RELEVANCE

Measurement of preoperative CRP concentration provided excellent sensitivity and moderate specificity for detection of GBR in dogs undergoing cholecystectomy because of GBM. Accuracy of using preoperative CRP concentration for detection of GBR was not superior to the accuracy of preoperative abdominal ultrasonography. However, when CRP concentration was combined with results of ultrasonography, the sensitivity, specificity, and accuracy for detection of GBR were 100%, 93%, and 96%, respectively.

Insulin in the saliva of pigs: Validation of an automated assay and changes at different physiological conditions

This study aimed to evaluate whether insulin could be measured in the saliva of pigs and if its concentration changes in some physiological conditions. For this purpose, a validation of an automated heterologous immunoassay for measuring insulin in the saliva of pigs was performed. In addition, the possible changes of salivary insulin concentration in sows after food intake and during gestation and lactation were studied. The evaluated immunoassay was able to detect insulin in the saliva of pigs in a precise and accurate way when species-specific calibrators were used. There was no correlation in insulin concentrations between serum and saliva. Insulin concentrations showed a significant increase in the saliva of sows after feeding. Sows at farrowing and lactation presented higher salivary insulin levels as compared with those in gestation. In conclusion, the results showed that insulin could be measured in the saliva of pigs, and changes in its concentration can be detected due to food intake and different physiological conditions.

From Bench Top to Clinics: How New Tests Can Be Helpful in Diagnosis and Management of Dogs with Chronic Enteropathies

In this article, we review different tests that have been researched in dogs with chronic enteropathy. The usefulness of these tests either to assess etiology, to differentiate between treatment response, or to monitor treatment response is discussed. The tests are divided in those that are commercially available and those that hold promises for further development.

Changes in Acute Phase Proteins in Bitches after Laparoscopic, Midline, and Flank Ovariectomy Using the Same Method for Hemostasis

Simple Summary

Ovariectomy is a common surgical procedure in veterinary medicine, with many techniques involved. The aim of this study is to objectively evaluate the acute phase response by measuring the changes in a panel of acute phase proteins after applying three different ovariectomy techniques. C-reactive protein values showed increases of lower magnitude after laparoscopic ovariectomy compared with other techniques, indicating that this surgical technique induces a reduced inflammatory response and tissue damage. The use of this procedure is in agreement with the current tendency to use minimally invasive procedures for ovariectomy.

Abstract

Acute phase proteins (APP) are biomarkers of systemic inflammation, which allow monitoring the evolution of diseases, the response to treatments, and post-operative complications. Ovariectomy (OVE) is frequently performed in veterinary medicine and can be a useful model to evaluate surgical trauma and inflammation in the bitch. The objective was to investigate and compare the acute phase response (APR) after applying three different OVE techniques by measuring serum levels of C-reactive protein (CRP), haptoglobin (Hp), albumin (Alb), and paraoxonase-1 (PON-1). Forty-five intact bitches were included in the study, being randomly distributed into three groups: laparoscopic OVE (L), midline OVE (M), and flank OVE (F). Serum CRP, Hp, Alb, and PON-1 were measured before surgery, 1, 24, 72, and 168 h post-intervention. CRP levels increased significantly 24 h post-surgery in the M and F groups, but no significant variation was observed in the L group at any time of the study period. Hp was significantly higher in group L than in group F 72 h post-surgery. Alb and PON-1 showed no statistical difference among groups or among sampling periods. CRP response suggests that the use of laparoscopic procedures produce lower inflammation compared to open conventional approaches when performing OVE in the bitch.

Characterization of total adenosine deaminase activity (ADA) and its isoenzymes in saliva and serum in health and inflammatory conditions in four different species: an analytical and clinical validation pilot study

Background

Measurement of adenosine deaminase (ADA) can provide information about cell-mediated immunity. This report’s objective was to study the enzymatic activity of total ADA (tADA) and its isoenzymes ADA1 and ADA2 in canine, equine, porcine, and bovine serum and saliva and their changes in different inflammatory situations in each species. Besides, an automated method for ADA2 measurement was developed and validated.

Results

tADA was present in serum and saliva of healthy animals of the four species. Erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) concentration of 0.47 mM was needed for ADA1 inhibition in canine and porcine samples (serum and saliva) and bovine saliva, whereas for equine saliva 0.94 mM was needed. ADA2 activity was not detected in bovine serum and was very low or absent in equine serum and bovine saliva. An automated procedure to measure ADA2 consisting of adding EHNA to a commercial reagent for tADA measurement provided repetitive (coefficients of variation < 8.8% in serum and < 10% in saliva) and accurate (linearity of serial sample dilutions with R² > 0.90) results, being equivalent to a manual incubation of the sample with EHNA at a similar concentration. Salivary tADA, as well as ADA1 and ADA2, were higher in dogs with leishmaniosis, horses with acute abdominal disease and pigs with lameness than in healthy animals. tADA and isoenzymes in saliva showed a positive significant correlation with serum ferritin in dogs (r = 0.602, P < 0.01; r = 0.555, P < 0.05; and r = 0.632, P < 0.01; respectively for tADA, ADA1 and ADA2) and serum C-reactive protein in pigs (r = 0.700, P < 0.01, for both tADA and ADA1; r = 0.770, P < 0.001, for ADA2), whereas salivary ADA2 significantly correlated with serum amyloid A in horses (r = 0.649, P < 0.01). In cows, salivary tADA and ADA1 significantly increased after calving, correlating with total white blood cell count (r = 0.487, P < 0.05, for both tADA and ADA1).

Conclusions

The activity of total ADA and its different isoenzymes, can be measured in serum and saliva of dogs, horses, pigs and cows by a simple and fast procedure described in this report. When measured in saliva, these analytes correlated with other biomarkers of inflammation and it could potentially be used as a biomarkers of inflammation and immune activation in the species of this study.

Evaluation of an automated immunoturbidimetric assay for detecting canine C-reactive protein

C-reactive protein (CRP) is a major acute-phase protein, and it is produced by the liver in response to a pro-inflammatory stimulus. Given that human and canine CRP have a similar molecular structure, the assays used for human CRP detection have been used to measure CRP concentrations in dogs. We evaluated the use of a human CRP assay (Biotecnica CRP assay) and validated its application in dogs. We analyzed 91 canine serum samples with a fully automated analyzer. Our validation was based on the evaluation of imprecision, limits of linearity, limits of quantification, and an evaluation of interferences. The new assay was also compared with the Randox CRP assay, a validated assay for the measurement of CRP. Intra- and inter-assay repeatability were <8% and <11%, respectively. The tested assay proportionally measured canine CRP in an analytical range up to 60 mg/L; however, hemoglobin, triglycerides, and bilirubin interfered with the determination. Good agreement, with the presence of proportional systematic bias, was observed between Biotecnica and Randox assays. The Biotecnica CRP assay provides reliable measurement of CRP in canine serum, provided that samples are free of interferents.

Adiponectin as a sepsis biomarker in dogs: Diagnostic and prognostic value

BACKGROUND

Adiponectin (ADPN) is an adipocytokine with insulin-sensitizing, vascular-protective, and anti-inflammatory properties for which concentration changes occur in response to inflammation. Little is known about the regulation of ADPN and the impact of this adipocytokine in septic dogs.

OBJECTIVE

We aimed to assess the diagnostic and prognostic value of ADPN vs other traditional acute-phase proteins (APPs), such as albumin (ALB), haptoglobin (HPT), fibrinogen (FBG), ferritin (FRT), and C-reactive protein (CRP) in dogs with naturally acquired sepsis.

METHODS

This prospective observational study included 20 dogs with sepsis, 27 with low-grade systemic inflammation (LGSI), and 18 clinically healthy dogs as controls. For method analyses, plasma samples were obtained from all dogs on admission and then every 24-48 hours until discharge or death in the septic group.

RESULTS

Septic dogs had lower ADPN (2.4 ± 0.46 vs 4.5 ± 0.41mg/L, P < .001) dand ALB (17 ± 1 vs 22 ± 0.8g/L, P = .002), and tended to have higher CRP (87 ± 4.8 vs 73 ± 4.1mg/L, P < .079) concentrations than dogs with LGSI on admission. Only ADPN and ALB were able to successfully discriminate animals with LGSI from those presenting with sepsis with areas under the curve (AUCs) for the receiver operating characteristic (ROC) curves of 0.811 and 0.789, respectively. In the septic group, ADPN concentration did not differ between survivors and non-survivors, either on admission or at discharge or death.

CONCLUSIONS

Although plasma ADPN can be used as a reliable negative APP in dogs with sepsis, further studies are warranted to confirm the usefulness of this biomarker in terms of disease progression and recovery.

The number of replicates, and pooling versus individual measurements for analytical imprecision calculations: Does it matter?

BACKGROUND

Recommendations from the American Society of Veterinary Clinical Pathology (ASVCP) are to calculate the between-run coefficient of variation (CV) based on measuring one replicate per day on quality control materials (QCMs) or pooled patient samples over a minimum of 20 days. However, this recommendation is not always followed by researchers.

OBJECTIVES

We aimed to determine if a reduction in the number of replicates using QCM or individual or pooled samples would provide CV results similar to those obtained based on ASVCP recommendations.

METHODS

CVs were calculated for three measurands, namely urea, creatinine, and C-reactive protein based on the analytic results of the following groups: (a) QCM measured once daily for 20 days (considered as the reference for comparison), b) QCM measured once daily for 5 days, (c) five different canine serum samples measured once daily for 5 days, and (d) a pooled canine serum measured once daily for 5 days. CVs were calculated for two different measurand concentrations.

RESULTS

Compared with the reference method, significantly different CVs were obtained with all methods except for when the QCM was measured once daily for 5 days. The use of the five different individual samples also provided significantly different CVs compared with the use of a pooled sample.

CONCLUSIONS

The results indicate that different protocols for determining between-run imprecision calculations can give different results compared with the reference procedure and that this should be taken into consideration when evaluating the total error associated with a test.

Biomarkers of health and welfare: A One Health perspective from the laboratory side

A biomarker is any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical, or biological. The One World, One Health concept established that human and animal health and the environmental state are highly interconnected, sharing common aspects that can be applied globally in these three components. In this paper, we review how the concept of One Health can be applied to biomarkers of health and welfare, with a special focus on five points that can be applied to any biomarker when it is expected to be used to evaluate the human, animal or environmental health. Three of these points are: (1) the different biomarkers that can be used, (2) the different sample types where the biomarkers can be analysed, and (3) the main methods that can be used for their measurement. In addition, we will evaluate two key points needed for adequate use of a biomarker in any situation: (4) a proper analytical validation in the sample that it is going to be used, and (5) a correct selection of the biomarker. It is expected that this knowledge will help to have a broader idea about the use of biomarkers of health and welfare and also will contribute to a better and more accurate use of these biomarkers having in mind their One Health perspective.

Analytical validation of an enzyme-linked immunosorbent assay for the quantification of S100A12 in the serum and feces of cats

BACKGROUND

Measuring S100A12 concentrations in serum and feces is a sensitive and specific marker of inflammation, such as seen with chronic gastrointestinal inflammation in people and dogs. Biomarkers of inflammation in cats are currently lacking.

OBJECTIVES

We aimed to analytically cross-validate the canine S100A12-ELISA for the measurement of S100A12 in feline specimens.

METHODS

The ELISA was analytically validated by assessing dilutional linearity, spiking/recovery, intra- and inter-assay variability. Reference intervals for serum and fecal feline S100A12 concentrations were calculated using samples from healthy cats, and the short-term biological variation of fecal S100A12 was assessed.

RESULTS

Observed-to-expected ratios (O/E) for serial dilutions of serum and fecal extracts ranged from 91%-159% (mean, 120%) and 100%-128% (mean, 114%), and for the spiking/recovery method ranged from 106%-263% (mean, 154%) and 52%-171% (mean, 112%). Intra- and inter-assay CV% for serum were ≤5.6% and ≤14.0%, and for fecal extracts were ≤3.8% and ≤19.1%, repsectively. RIs for feline serum and fecal S100A12 concentrations were <43 µg/L and < 20 ng/g, respectively. A mild short-term biologic variation, but large individuality were detected when measuring fecal S100A12 concentrations in healthy cats.

CONCLUSIONS

The canine S100A12-ELISA is accurate, reproducible, and sufficiently linear and precise for the measurement of S100A12 in feline serum and fecal samples. The use of this assay is a reasonable option for the measurement of S100A12 concentrations in feline specimens and provides a basis for the further evaluation of  S100A12 in cats with gastrointestinal disease. Using a population-based RI for fecal feline S100A12 appears to be of limited value.

The diagnostic and prognostic value of paraoxonase-1 and butyrylcholinesterase activities compared with acute-phase proteins in septic dogs and stratified by the acute patient physiologic and laboratory evaluation score

BACKGROUND

Sepsis is a complex syndrome that involves an increased oxidative stress status and dysregulation of cholinergic neurotransmission. Paraoxonase-1 (PON-1) and butyrylcholinesterase (BChE) activities have been identified as significant biomarkers to monitor such disorders in human septic patients.

OBJECTIVE

We aimed to determine the diagnostic and prognostic value of PON-1 and BChE vs other traditional acute-phase proteins such as albumin (ALB) and C-reactive protein (CRP) in septic dogs.

METHODS

This prospective observational study included 20 dogs with a diagnosis of sepsis, 27 with low-grade systemic inflammation (LGSI), and 10 healthy dogs that served as controls. Plasma samples were obtained from all dogs for analysis on admission, and then every 24-48 hours until discharge or death in the septic group.

RESULTS

Dogs with sepsis had lower PON-1 activity compared with dogs in the LGSI group (1.1 ± 0.10 vs 1.6 ± 0.08 U/mL, P = .002), but no differences in BChE activity were detected between the groups. PON-1, ALB, and CRP could successfully discriminate healthy animals from those with sepsis looking at the area under the curve (AUC) of the receiver operator characteristics curves (ROCs), which were 0.828, 0.903 and 1.000, respectively. Finally, although no differences were found among the groups for PON-1 or BChE activity, the nonsurvivor septic dogs had higher CRP (P = .002), lower ALB (P = .025) levels, and tended to have lower PON-1 (P = .082) activities than the survivors at patient death or discharge.

CONCLUSION

Septic dogs showed lower plasma PON-1 and higher BChE activities, but only PON-1 activity correlated with disease severity. Further studies are warranted to describe the usefulness of these new biomarkers of sepsis progression and recovery in dogs.

Calibration of Novel Protein Biomarkers for Veterinary Clinical Pathology: A Call for International Action

Research into the identification and use of protein biomarkers for use in veterinary clinical pathology has produced numerous potential analytes that could become common tests in the future. One problem that has to be overcome in the general acceptance of a novel biomarker is that differing standards for calibration may be developed by individual laboratories or the diagnostic companies that will provide kits for widespread use. This has been apparent in the development of acute phase protein biomarkers such as canine C-reactive protein. In order to overcome this problem an international initiative is required to ensure that assays developed in separate laboratories would have a consistent calibration protocol so that results produced are equivalent. International reference preparations for serum protein analysis for each relevant species should be established for use as primary standard in the calibration of biomarkers for veterinary diagnosis.

Acute phase proteins, saliva and education in laboratory science: an update and some reflections

This manuscript provides updated knowledge and some ideas and reflections about three areas which are currently of interest in the field of the animal laboratory science. These areas are the study of acute phase proteins (APPs) as biomarkers of inflammation, the use of saliva as a non-invasive sample for analyte measurements, and the development of education in the field of laboratory medicine. In the APPs, a seven-point plan for their interpretation in all veterinary species containing updated knowledge and future perspectives is described. Regarding the saliva, general concepts, examples of practical applications and the limitations and points to improve for the use of this fluid are explained. Finally, the recent evolution, current situation and possible ideas for future development of education in this field are commented. In addition to review the knowledge in these three specific areas, this report can help to provide a wide vision of the potential and future perspectives in veterinary laboratory science.

Relationship between serum anti-Leishmania antibody levels and acute phase proteins in dogs with canine leishmaniosis

This study examined the relationship between two serologic assays which quantify anti-Leishmania antibodies (a commercial enzyme-linked immunosorbent assay (ELISA) and a time-resolved immunofluorometric assay (TR-IFMA)) and selected acute phase proteins (APPs) and analytes related to protein concentration. Data were obtained from 205 canine serum samples from different veterinary clinics located in an area in which canine leishmaniosis (CanL) is endemic. The samples were submitted to the Interdisciplinary Laboratory of Clinical Analysis (Interlab-UMU), University of Murcia, Spain, for analysis. The biochemical analytes evaluated were serum ferritin, C-reactive protein (CRP), haptoglobin, paraoxonase-1 (PON-1) and albumin as APPs and total proteins and globulins as indicative analytes of protein concentration. Samples were submitted for the initial diagnosis of CanL, or to monitor the response to treatment in patients with CanL. The evaluation of the biochemical analytes did not show differences between Leishmania-seronegative and Leishmania-seropositive dogs. However, dogs with high antibody titers showed more pronounced clinicopathological abnormalities. Both serological assays had correlations of different significance with the biochemical analytes, showing higher significant correlations with total proteins and globulins than with the rest of the analytes. When the samples submitted for diagnosis and treatment monitoring were analyzed separately, serological assays showed lower correlation in samples for treatment monitoring (r = 0.531, p <  0.0001) than in samples for diagnosis (r = 0.769, p <  0.0001). In addition, higher correlations were found between TR-IFMA and analytes such as serum ferritin and CRP in the treatment monitoring group than with the ELISA. These results may help to clarify the relationship between anti-Leishmania antibody levels and selected biochemical analytes related to inflammation and protein concentration in CanL.

Evaluation of a novel quantitative canine species-specific point-of-care assay for C-reactive protein

BACKGROUND

Species-specific point-of-care tests (POCT) permit a rapid analysis of canine C-reactive protein (CRP), enabling veterinarians to include CRP in clinical decisions. Aim of the study was to evaluate a novel POCT for canine CRP (Point Strip™ Canine CRP Assay) run on a small in-house-analyzer (Point Reader™ V) using lithium heparin plasma and to compare assay performance to an already established canine CRP assay (Gentian Canine CRP Immunoassay) run on two different bench top analyzers serving as reference methods (ABX Pentra 400, AU 5800). Linearity was assessed by stepwise dilution of plasma samples with high CRP concentrations. Limit of quantification (LoQ) was determined by repeated measurements of samples with low CRP concentrations. Coefficient of variation (CV) at low (10-50 mg/l), moderate (50-100 mg/l), and high (100-200 mg/l) CRP concentrations was investigated as well as possible interferences. Method comparison study was performed using 45 samples of healthy and diseased dogs. Quality criteria were fulfilled if the total observed error (TE_obs = 2CV% + bias%) was below the minimal total allowable error of 44.4% (TE _min). Additionally, a reference range (n = 60 healthy dogs) was established.

RESULTS

Linearity was present at CRP concentrations of 10-132 mg/l (≙ 361 mg/l CRP with reference method) with a LoQ set at 10 mg/l. At moderate to high CRP concentrations, intra- and inter-assay CVs were ≤ 8% and ≤ 11% respectively, while CVs ≤ 22% and ≤ 28% were present at low concentrations. No interferences were observed at concentrations of 4 g/l hemoglobin, 800 mg/l bilirubin and 8 g/l triglycerides. Method comparison study demonstrated an excellent correlation with both reference methods (r = 0.98 for ABX Pentra 400; 0.99 for AU 5800), though revealing a proportional bias of 19.7% (ABX Pentra 400) and 10.7% (AU 5800) respectively. TE_obs was 26.7-31.9% and 16.7-21.9% and thus < TE_min. Healthy dogs presented with CRP values ≤11.9 mg/l.

CONCLUSIONS

The POCT precisely detects canine CRP at clinically relevant moderate and high CRP concentrations. The assay correlates well with both reference methods. Due to the bias, however, follow-up examinations should be performed with the same assay and analyzer.

Acute phase proteins and markers of oxidative stress to assess the severity of the pulmonary hypertension in heartworm-infected dogs

Background

Canine heartworm infection is characterized by pulmonary endarteritis and pulmonary hypertension (PH). The aim of the present study was to evaluate the relationship between PH with the concentrations of different positive (C-reactive protein [CRP] and haptoglobin [Hp]) and negative (albumin and paraoxonase-1 [PON-1]) acute phase proteins (APP), as well as the oxidative stress, by measuring glutathione peroxidase (GPx) and total antioxidant capacity (TAC) in 27 heartworm-infected dogs on Day 0 (diagnosis) and Day 120 (1 month after the last adulticide injection). Presence/absence of PH was determined by the Right Pulmonary Artery Distensibility (RPAD) Index.

Results

On Day 0, 62.9% of the dogs showed PH. Concentrations of CRP and Hp were higher in dogs with PH, especially in dogs with moderate-severe PH (P < 0.005 and P < 0.05, respectively). Albumin and PON-1 concentrations were higher in dogs without PH (P < 0.05 for albumin). On Day 120, 59.2% of the dogs presented with PH; CRP decreased while Hp increased (P < 0.005 and P < 0.05, respectively). Also, albumin and PON-1 rose, especially in absence of PH. There were not significant changes in the serum values of GPx and TAC.

Conclusions

CRP and Hp have a potential prognostic role in dogs with dirofilariasis because increases in positive APP correlated with presence and severity of PH. CRP decreased, but Hp persisted at an elevated level in dogs with PH 1 month after the end of the adulticide treatment. CRP and Hp could work as early biomarkers of PH and be useful to stage the disease and to monitor the evolution of the patient and indirectly evaluate the persistence of arterial damage after the parasites have been eliminated. Albumin and PON-1 also showed potential value as markers of PH, although further research is necessary to determine its utility.

Evaluation of a species-specific C-reactive protein assay for the dog on the ABX Pentra 400 clinical chemistry analyzer

Background

A canine-specific immunoturbidimetric CRP assay, Gentian Canine CRP Immunoassay) with species-specific controls and calibrators was introduced and recently evaluated on the clinical chemistry analyzer Abbott Architect c4000 as well as on the Olympus AU600.

Aims of our study were 1) to independently evaluate the canine-specific CRP assay on the ABX Pentra 400 clinical chemistry analyzer in comparison to the previously validated human-based immunoturbidimetric assay (Randox Canine CRP assay) and 2) to assess the impact of different sample types (serum versus heparinized plasma) on the results.

Imprecision, accuracy, interference and the prozone effect were determined using samples from healthy and diseased dogs (n = 278). The Randox Canine CRP assay calibrated with canine specific control calibration material served as a reference method. Additionally, the impact of the sample type (serum and lithium heparin) was evaluated based on samples of healthy and diseased dogs (n = 49) in a second part of the study.

Results

Linearity was present for CRP concentrations ranging from 4 to 281 mg/l. For clinically relevant CRP concentrations of 7–281 mg/l, recovery ranged between 90 and 105% and intra- and inter-assay CVs ranged between 0.68% - 12.12% and 0.88% - 7.84%, respectively. CV was thus lower than 12.16%, i.e. the desired CV% based on biological variation. Interference was not present up to a concentration of 5 g/l hemoglobin, 800 mg/l bilirubin and 10 g/l triglycerides. No prozone effect occurred up to 676 mg/l CRP. Method comparison study revealed a Spearman’s rank correlation coefficient of r_s = 0.98 and a mean constant bias of 5.2%. The sample type had a significant (P = 0.008) but clinically not relevant impact on the results (median CRP of 30.9 mg/l in lithium heparin plasma versus 31.4 mg/l in serum).

Conclusions

The species-specific Gentian Canine CRP Immunoassay reliably detects canine CRP on the ABX Pentra 400 clinical chemistry analyzer whereby both serum and heparin plasma can be used. The quality criteria reached on the Abbott Architect c4000 and Olympus AU600 could be met.