Acute phase proteins in healthy and sick cats

Postoperative monitoring of ovariohysterectomy carried out with two types of surgical sutures in shelter cats and differences in selected blood parameters between shelter and pet cats

BACKGROUND

Reduction of inflammation and early detection of complications after surgical procedures are important objectives for proper veterinary practice. This study aimed to evaluate the differences between shelter and pet female cats in selected acute-phase parameters scheduled to ovariohysterectomy. Postoperative monitoring after ovariohysterectomy with the same laboratory parameters was performed in shelter cats, in which two different types of surgical sutures were used for the entire procedure. The experimental group comprised 40 female cats from animal shelters ('shelter cats,' n = 40). These cats were divided into two subgroups: group A (n = 20) operated on with absorbable sutures and group NA (n = 20) operated on with non-absorbable sutures. In addition, the same parameters were evaluated in pet female cats (n = 19). Blood was collected from shelter cats immediately before surgery (term 0), at 24 and 72 h (terms 1 and 3, respectively), and at 7 and 14 days (terms 7 and 14, respectively) after ovariohysterectomy. Blood samples from the pet cat group were collected only once.

RESULT

The mean haptoglobin concentration before ovariohysterectomy in pet cats was significantly lower than that in shelter cats. Fibrinogen concentration was significantly lower in pet cats than in cats from group A. Serum albumin, beta-1, beta-2, and gamma-globulin concentrations were significantly higher in the shelter cats than in the pet cats. Subcutaneous tissue thickening at the site of the postoperative wound was observed in five patients cats (25%) in group A, and two (10%) cats in the NA group.

CONCLUSION

These results indicate that ovariohysterectomy leads to local and general inflammatory responses. The majority of cats from animal shelters suffered from subclinical inflammation.

The Diagnostic Value of Serum Amyloid A and Other Laboratory and Clinical Variables in Cats with Increased Liver Enzyme Activity

Distinguishing inflammatory from non-inflammatory liver disease in cats may impact management. The study aim was to evaluate if certain diagnostic variables, including Serum Amyloid A (SAA), differ (1) between various clinical disease categories (Primary liver disease, Extrahepatic, Trauma and Inconclusive) and (2) between cytological findings of severe hepatic lipidosis and other cytological findings in cats with increased liver enzymes. Medical records from 5042 cats, where SAA had been measured, were reviewed, and 566 cats fulfilled inclusion criteria consisting of increased liver enzymes and available biochemical panel results. SAA was higher in cats diagnosed with trauma compared to other diseases (p = 0.008). Cytology results were available in 85 cats, and cats with severe lipidosis had lower serum SAA concentration (p < 0.0001) and were younger (p < 0.0002) compared to cats with other cytological findings. The study shows that SAA was higher in cats diagnosed with trauma compared to cats with other causes of increased liver enzymes and that SAA may be useful to distinguish cats with cytologic evidence of hepatic lipidosis from cats with other liver pathologies. Serum Amyloid A may be a valuable complement to liver cytology when investigating cats with increased liver enzymes.

Usefulness of serum amyloid A for the diagnosis of pyelonephritis in cats: A prospective evaluation

BACKGROUND

The diagnosis of pyelonephritis in cats is challenging and development of a noninvasive and accurate biomarker is needed.

HYPOTHESES

Serum amyloid A (SAA) is increased in cats with pyelonephritis, but not in cats with other urinary tract diseases.

ANIMALS

A cohort of 125 cats (149 observations).

METHODS

This was a prospective study. Group 1 included cats with a diagnosis of pyelonephritis either confirmed by bacterial culture of pelvic urine (Group 1a) or presumed (1b). Group 2 included cats for which pyelonephritis was ruled out (with certainty: Group 2a or judged unlikely: Group 2b). SAA concentration was compared between groups, and accuracy of SAA for the diagnosis of pyelonephritis was calculated using a Receiver Operating Characteristic (ROC) curve analysis.

RESULTS

Median SAA concentration was significantly higher in Group 1a (86.8 mg/L [73.3; 161.5]; n = 8) than in Group 2a (4 mg/L [1.8; 5.6], n = 19; P < .001) and in Group 2b (5.4 mg/L [3.1; 9.7], n = 113; P < .001). It was also significantly higher in Group 1b (98.8 mg/L [83.1; 147.3]; n = 9) than in Group 2b (P < .001) and Group 2a (P < .001). Optimal diagnostic cut-off for SAA concentration was 51.3 mg/L. yielding a sensitivity of 88% (95% confidence interval: [64%; 99%]) and a specificity of 94% (95% confidence interval: [88%; 97%]).

CONCLUSIONS AND CLINICAL IMPORTANCE

Measurement of SAA could be used to rule out pyelonephritis in the case of low suspicion of the disease. Increased SAA concentration is suggestive of pyelonephritis despite a lack of specificity.

Effect of pyometra on vascularity alterations, oxidative stress, histopathology and inflammatory molecules in feline

This study aimed to investigate blood flow, hemodynamical features by Doppler ultrasound, the oxidative stress biomarkers from serum samples, and histopathology from uterine tissue, in healthy queens and queens with pyometra. Twenty queens were categorized into two groups, according to signs, history, and ultrasound findings, as pyometra and control healthy queens. Doppler ultrasonography, total antioxidant capacity (TAC), malondialdehyde (MDA), albumin, bacteriological isolation, histopathology, and immunohistochemistry of tumor necrosis factor-alpha (TNF-α) and nuclear factor kappa B (NF-κB) P65 were performed. Uterine diameter and thickness increased significantly in the pyometra group compared to control. Uterine peak velocity and flow rate were significantly higher in the control group. The pyometra group showed a significant decrease in albumin, TAC, and a significant increase in MDA. Fibrosis and mononuclear inflammatory cell infiltration were seen in the pyometra samples. The mean area percentage of TNF-α expression in the uteri of the pyometra group was higher. The expression of NF-κB P65 in the uteri in the pyometra group was significantly higher. Doppler ultrasonography can provide valuable information for diagnosing pyometra in queens by elevating the uterine thickness with reducing blood flow rate. Oxidative stress, TNF-α, and NF-κB expression alterations varied between pyometra and control groups.

Acute phase proteins and total antioxidant capacity in free-roaming cats infected by pathogenic leptospires

BACKGROUND

Leptospirosis is a neglected but widespread zoonotic disease throughout the world. Most mammals are hosts of Leptospira spp., including domestic cats, species in which no consensus has been reached on the clinical presentation or diagnosis of the disease. The study of acute-phase proteins (APPs) and biomarkers of oxidative status would contribute to knowledge about the disease in cats. This report evaluated four APPs: Serum amyloid A-SAA, Haptoglobin-Hp, albumin and Paraoxonase 1-PON1 and the antioxidant response through Total Antioxidant Capacity-TAC, in 32 free-roaming cats. Cats were classified as seroreactive for anti-leptospiral antibodies (group 1, n = 8), infected with Leptospira spp (group 2, n = 5) and leptospires-free cats (group 3, n = 19).

RESULTS

SAA differences were observed between groups 1 and 2 (p-value = 0.01) and between groups 2 and 3 (p-value = 0.0001). Hp concentration differences were only detected between groups 2 and 3 (p-value = 0.001). Albumin concentrations only differed between groups 1 and 3 (p-value = 0.017) and 2 and 3 (p-value < 0.005). Cats in groups 1 (p-value < 0.005) and 2 (p-value < 0.005) had lower PON1 concentrations than group 3. No statistically significant differences between pairs of groups were detected for TAC concentrations. The principal component analysis (PCA) retained two principal components, (PC1 and PC2), explaining 60.1% of the observed variability of the inflammatory proteins and the antioxidant TAC.

CONCLUSIONS

Increases in Serum SAA, Hp, and decreases in PON1 activity may indicate an active inflammatory state in infected cats (currently or recently infected).

Serum amyloid A in cats with renal azotemia

Background and Aim

The concentration of the feline acute-phase protein serum amyloid A (SAA) increases in cats with acute inflammatory diseases. However, it is unclear whether SAA concentration increases in cats with azotemic kidney disease or whether it can aid in differentiating acute kidney injury (AKI) from chronic kidney disease (CKD). Similarly, whether SAA concentration can be used as a prognostic marker is also unclear. Therefore, this study aimed to evaluate the SAA concentrations in cats with azotemic kidney disease and determine whether SAA concentrations can be used to differentiate between AKI, CKD, and "acute on CKD" (AoC). In addition, we evaluated whether SAA concentration could serve as a prognostic parameter. Moreover, we determined the correlations between SAA concentration and temperature; creatinine, urea, and albumin concentrations; leukocyte count; and urine protein/creatinine (UP/C).

Materials and Methods

Forty-eight client-owned azotemic cats (creatinine >250 μmol/L) were included in this prospective study. Cats with pre- and post-renal azotemia were excluded from the study. The causes of azotemia were differentiated into AKI, CKD, and AoC. The SAA concentrations were analyzed through turbidimetric immunoassay at the time of admission. Data were analyzed using the Mann-Whitney U, Kruskal-Wallis, Chi-Square, Fisher's exact, and Spearman correlation tests. p ≤ 0.05 was considered statistically significant.

Results

Serum amyloid A concentration increased in 5/12 cats with AKI, 7/22 cats with CKD, and 9/14 cats with AoC (p = 0.234). The median SAA concentration in cats with AKI, CKD, and AoC whose SAA concentration was ≥5 mg/L was 174 mg/L (10-281 mg/L), 125 mg/L (6-269 mg/L), and 143 mg/L (7-316 mg/L), respectively (p = 0.697), with no significant differences observed between the groups. The median SAA concentration did not differ significantly between survivors (125 mg/L, 10-316 mg/L) and non-survivors (149 mg/L, 6-281 mg/L; p = 0.915) with SAA concentration ≥5 mg/L.

Conclusion

Serum amyloid A concentration increased in 44% of the cats with azotemia. However, it cannot be used to differentiate AKI from CKD or as a prognostic marker. Serum amyloid A concentration was correlated with neutrophil count, albumin concentration, and UP/C, and the presence of comorbidities may influence SAA concentration.

Cat alpha-1-acid glycoprotein enzyme-linked immunosorbent assay: performance characteristics and reference intervals

OBJECTIVES

The aim of this study was to evaluate performance of a feline-specific ELISA for the measurement of alpha-1-acid glycoprotein (AGP) and to establish a reference interval (RI).

METHODS

Surplus serum samples with low (~200 µg/ml), medium (~450 µg/ml) and high (~745 and 930 µg/ml) AGP concentrations were used to assess the intra- and inter-assay coefficients of variation (CVs). The quality goal for bioanalytical method validation was a CV of <20%. Linearity was assessed by serial dilution of a sample with a high AGP concentration. Spike recovery was evaluated by mixing samples with low, medium and high AGP concentrations at different ratios. To establish the RI, residual serum samples from 51 healthy adult cats that were presented for health examinations or blood donation between August 2020 and June 2021 were included.

RESULTS

The intra-assay CV was 8.5%, 4.3% and 4.0%, and the inter-assay CV was 18.8%, 15.5% and 11.5% for serum samples with low, medium and high AGP concentrations, respectively. Excellent linearity (R2 = 0.98) was demonstrated for AGP concentrations ranging between 251.6 and 954.4 µg/ml. Average recovery was 95.0-99.7%. The right-sided RI for AGP was 328 µg/ml (90% confidence interval 300-354). Age had a statistically significant impact (increasing values with older age, P = 0.0026), but sex did not (P = 0.44), on AGP concentrations.

CONCLUSIONS AND RELEVANCE

The ELISA was accurate and showed acceptable precision with the modification of dilution used in this study. AGP concentrations in this population appeared to increase with increasing age.

Acute phase proteins in cats: Diagnostic and prognostic role, future directions, and analytical challenges

While clinical studies on acute phase proteins (APPs) have significantly increased in the last decade, and most commercial labs are now offering major APPs in their biochemical profiles, APP testing has not been widely adopted by veterinary clinical pathologists and veterinarians. Measurement of APP concentration is a useful marker for detecting the presence or absence of inflammation in cats with various diseases. APPs can also be reliably measured in different biological fluids (eg, effusions and urine) to improve their diagnostic utility. Measurement of APPs can be extremely beneficial in cats with feline infectious peritonitis (FIP) to discriminate between FIP and non-FIP cats with similar clinical presentations. Additional benefits come from multiple and sequential measurements of APPs, particularly in the assessment of therapeutic efficacy. APPs are more sensitive than WBC counts for early detection of inflammation and to demonstrate an early remission or recurrence of the diseases. Given the potential utility of APPs, more studies are warranted, with a particular focus on the applications of APPs to guide the length of antimicrobial therapies, as suggested by the antimicrobial stewardship policy. New inflammatory markers have been discovered in human medicine, with a higher specificity for distinguishing between septic versus nonseptic inflammatory diseases. It is desirable that these new markers be investigated in veterinary medicine, to further test the power of APPs in diagnostic setting.

Comparative evaluation of acute phase proteins by C-reactive protein (CRP) and serum amyloid A (SAA) in nonhuman primates and feline carnivores

The feasibility of a commercially available assay for C-reactive protein (CRP, CRP for humans: hCRP, and CRP for dogs: vCRP) and a trial reagent of serum amyloid A (SAA, vSAA for animals) were applied to the measurement of acute phase proteins in zoo animals, particularly in nonhuman primates and feline carnivores was evaluate. Results showed that hCRP and vSAA methods were applicable to measure CRP and SAA in Haplorhini. There was a highly significant correlation between both parameters with remarkably high correlation coefficient. A higher proportion of Bonnet macaques in Haplorhini, and the linear regression with good correlation between hCRP and vSAA levels were observed. Reference values in healthy Bonnet macaques were hCRP (46.86 ± 30.97 nmol/L) and vSAA (9.06 ± 1.95 μg/mL). Although Ring-tailed lemur, which belonging to Strepsirrhini, showed low vSAA concentrations (reference values: 1.08 ± 0.47 μg/mL), vSAA in patients was apparently elevated. The vCRP and vSAA methods were applicable to measurements of CRP and SAA in feline carnivores for highly significant correlation between both parameters. Theses two methods were also been deteded in lions, tigers and cheetahs. vSAA assays can be applied to measure SAA levels in other carnivores and herbivores. In conclusion, vSAA systems have potential utility as diagnostic tools for health screening and prediction in zoo animals.

Impact of radioiodine treatment on acute phase proteins in hyperthyroid cats

OBJECTIVES

The aim of this study was to investigate the impact of radioiodine treatment (RIT) on the acute phase proteins (APPs) serum amyloid A (SAA), alpha-1-acid glycoprotein (AGP) and haptoglobin (Hp) in hyperthyroid cats.

METHODS

Between June 2013 and November 2014, 33 hyperthyroid cats without clinical or laboratory signs of inflammatory or neoplastic disease and a body weight >2.5 kg were enrolled. Immediately before, and 12, 36, 72 h and 6 days after RIT, serum samples were obtained for determination of APP concentrations.

RESULTS

Both SAA and AGP concentrations changed significantly after RIT. The concentration of AGP increased gradually after treatment with a maximum concentration at the end of the study period (median baseline 398 μg/ml; median 6 days post-RIT 562 μg/ml [P = 0.001]). A relevant >two-fold increase in AGP was seen in 8/33 (24%) cats. SAA concentration increased significantly within 12 h (baseline 9.2 μg/ml; 12 h post-RIT 22.5 μg/ml [P = 0.012]). In 7/33 (21%) cats, a clinically relevant >10-fold increase in SAA was observed. Hp concentration showed no significant change (P = 0.12).

CONCLUSIONS AND RELEVANCE

RIT induced a mild, mainly not clinically relevant acute phase reaction (APR). AGP and SAA were useful APPs to determine RIT-induced APR.

Accuracy of acute-phase proteins in identifying lethargic and anorectic cats with increased serum feline pancreatic lipase immunoreactivity

The mainstay of laboratory diagnostics of feline pancreatitis (FP) is measuring serum feline pancreatic lipase immunoreactivity (fPLI). Thus far, several studies have investigated the relationship between acute-phase proteins (APPs) and the presence and severity of FP. Although changes in serum amyloid A (SAA) concentration have been linked with FP, its diagnostic accuracy remains unknown. We aimed to determine the accuracy of selected APPs in identifying cats with a high risk of FP based on increased fPLI. Serum fPLI was measured in cats (n = 52) that were presented to veterinary clinics with signs of lethargy and anorexia. The cats were divided into two groups (fPLI ≤3.5 μg/L; n = 27 and fPLI >3.5 μg/L, n = 25), corresponding to low and high risks of FP. Serum albumin, globulin, haptoglobin (Hp), and SAA concentrations, as well as the albumin-to-globulin ratio (A/G) and SAA-to-albumin (SAA/A) ratios, were determined and compared between groups. The accuracy of these measurements was examined using a multivariable logistic regression model and receiver operator characteristic (ROC) curve analysis. SAA concentrations and SAA/A ratios were significantly (P = .026 and P = .022) higher in cats with increased fPLI, with the area under ROC curve (AUROC) of 68.1% (CI 95%: 53.4%, 82.9%) and 68.6% (CI 95%: 54.0%, 83.2%), respectively. The logistic regression model combining SAA and A/G had AUROC of 75.2% (CI 95%: 62.0%, 88.4%) for identifying cats with increased fPLI. SAA as a sole analyte or combined with A/G had low to moderate accuracy in identifying anorexic, lethargic cats with increased fPLI. Serum albumin, globulin, and Hp concentrations had no discriminatory potential in these cats.

Evaluation and comparison of serum procalcitonin and heparin-binding protein levels as biomarkers of bacterial infection in cats

OBJECTIVES

As bacterial infection can lead to sepsis and high mortality, early and easy diagnosis of sepsis can improve survival. In cats, the diagnosis of systemic bacterial infection is quite challenging, and, usually, non-specific markers for inflammation are employed. In humans, procalcitonin, heparin-binding protein and absolute neutrophil count are biomarkers that are studied in bacterial infections and sepsis owing to their high sensitivity and specificity.

METHODS

A total of 56 cats were categorised into 16 healthy cats and 40 bacterially infected cats, diagnosed by various examinations. In all cats, serum procalcitonin and heparin-binding protein levels were measured using ELISA and an absolute neutrophil count was performed.

RESULTS

The median values of procalcitonin levels and absolute neutrophil count were significantly higher in the infection group than in the normal group, but heparin-binding protein levels were not. A procalcitonin level >366 pg/ml was a better biomarker of bacterial infection than heparin-binding protein and absolute neutrophil count (sensitivity: 67.5%; specificity: 93.8%). Procalcitonin was not correlated with heparin-binding protein (r = 0.213, P = 0.115) and absolute neutrophil count (r = 0.393, P = 0.003).

CONCLUSIONS AND RELEVANCE

High procalcitonin levels in cats were associated with bacterial infection. Hence, procalcitonin could be a valuable marker for diagnosing bacterial infections in cats.

Serum haptoglobin concentrations in feline inflammatory bowel disease and small-cell alimentary lymphoma: a potential biomarker for feline chronic enteropathies

OBJECTIVES

The aim of this study was to evaluate serum haptoglobin as a biomarker to differentiate between small-cell alimentary lymphoma and inflammatory bowel disease in cats.

METHODS

Client-owned domestic cats with and without chronic gastrointestinal signs were enrolled in the study. Serum was collected from each patient and serum haptoglobin levels were measured using ELISA. In cats with gastrointestinal signs, histopathologic evaluation of endoscopic biopsies harvested from the intestinal tract was used to separate them into inflammatory bowel disease and small-cell lymphoma cohorts. Serum haptoglobin levels were statistically analyzed and compared among the three groups: healthy cats; cats with inflammatory bowel disease; and cats with small-cell alimentary lymphoma.

RESULTS

Sixty-two cats were enrolled in the study, including 20 clinically normal cats, 14 cats with small-cell alimentary lymphoma and 28 cats with inflammatory bowel disease. The mean ± SD serum haptoglobin was 73.2 ± 39.1 mg/dl in normal cats, 115.3 ± 72.8 mg/dl in cats with inflammatory bowel disease and 133.1 ± 86.1 mg/dl in cats with small-cell alimentary lymphoma. Cats with inflammatory bowel disease and lymphoma had significantly higher serum haptoglobin than controls, with P values of 0.0382 and 0.0138, respectively. There was no statistical difference between the inflammatory bowel disease and lymphoma cohorts (P = 0.4235). For every one unit increase in serum haptoglobin, the odds of gastrointestinal inflammatory disease (inflammatory bowel disease or small-cell alimentary lymphoma) increased by 1.41% (P = 0.0165).

CONCLUSIONS AND RELEVANCE

Serum haptoglobin is a useful biomarker for distinguishing between normal cats and those with gastrointestinal inflammatory disease, but it could not significantly differentiate between inflammatory bowel disease and lymphoma. Additional studies may be beneficial in determining the prognostic significance of serum haptoglobin as it may relate to the severity of gastrointestinal inflammation.

A pilot study to evaluate the serum Alpha-1 acid glycoprotein response in cats suffering from feline chronic gingivostomatitis

BACKGROUND

Feline chronic gingivostomatitis (FCGS) is a multifactorial immune-mediated disease that can lead to chronic pain, anorexia, and weight loss and has substantial health and welfare effects. Currently, the recommended treatment includes dental extractions to decrease the inflammatory stimulation associated with dental plaque. However, complete remission is observed in less than half of the cases, and the majority need comprehensive medical management. This study aimed to evaluate the serum levels of the acute phase protein alpha-1 acid glycoprotein (AGP) in cats with FCGS and to examine whether dental extractions contribute to a significant decrease in the systemic inflammatory response at two postoperative time points.

RESULTS

AGP serum concentrations in the cats with FCGS were significantly higher at all time points than that in the control groups and were significantly correlated with the global caudal stomatitis score at day 0 but not at day 30 or 60. A significant improvement of some clinical scores, such as perceived comfort and global caudal stomatitis, was observed 60 days after the dental extraction. However, the levels of AGP did not significantly change over time.

CONCLUSIONS

Cats with FCGS were more likely to have a systemic inflammatory response compared with age- and dental disease-matched controls. Dental extractions, in most cases, did not contribute to a significant decrease of AGP both at 30 and 60 days. Therefore, this study reinforces the need to pursue comprehensive medical management after dental extractions to attenuate the systemic inflammatory response as a result of this disease.

Cardiovascular-renal axis disorder and acute-phase proteins in cats with congestive heart failure caused by primary cardiomyopathy

BACKGROUND

Currently, the pathogenesis of congestive heart failure (CHF) in cats is not fully understood.

OBJECTIVE

To identify novel biomarkers for CHF in cats caused by primary cardiomyopathy, particularly related to cardiovascular-renal axis disorder and systemic inflammatory response.

ANIMALS

Twenty-five cats in CHF caused by primary cardiomyopathy, 12 cats with preclinical cardiomyopathy, and 20 healthy controls.

METHODS

Case control and observational case series. The following serum biomarkers were compared among the 3 cat groups: a cardiorenal profile that included N-terminal pro-brain natriuretic peptide (NT-proBNP), symmetric dimethylarginine (SDMA), and creatinine and an inflammatory profile that included 7 acute-phase proteins (APPs). Survival analyses and longitudinal studies were performed in CHF cats.

RESULTS

All cardiorenal biomarkers were positively correlated and higher in CHF cats, and high NT-proBNP and SDMA were associated with poor clinical outcome. Cats with CHF had significantly higher leucine-rich alpha-2-glycoprotein 1, serum amyloid A, and ceruloplasmin, and these APPs were positively correlated with NT-proBNP and left atrial size. In a multivariable survival analysis, alpha-1-acid glycoprotein concentration (P = .01), body weight (P = .02) and left atrial-to-aortic root ratio (P = .01) were independent prognostic factors for CHF in these cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

In cats, CHF is an inflammatory disorder and outcome in CHF may be determined by the extent of inflammation and possibly the amount of residual renal function. These novel biomarkers have potential use for the clinical management, prognosis, and future research into CHF and cardiomyopathy in cats.

A Clinical Investigation on Serum Amyloid A Concentration in Client-Owned Healthy and Diseased Cats in a Primary Care Animal Hospital

Although measurement of serum amyloid A (SAA) concentration in client-owned cats has already been shown to be clinically useful, limited data are available on common diseases at primary care hospitals. In this study, we measured the SAA concentration in cats with various diseases and investigated their clinical significance using a primary care hospital as a population. We measured the SAA concentrations in healthy cats (n = 98) and those with various clinical signs (n = 444). The SAA concentrations in healthy cats did not differ significantly by age, breed, sex, and presence/absence of neutering/spaying. The SAA concentrations were significantly higher in the diseased cat group than in the healthy cat group (p < 0.001). We observed significant increases in SAA concentrations in cats with confirmed diagnosis of inflammatory disease such as upper respiratory tract infections (p < 0.001), pneumonia (p < 0.001), pyometra (p = 0.001), and feline infectious peritonitis (p < 0.001), compared with those observed in healthy cats. Conversely, no increase was observed in cardiomyopathy, hyperthyroidism, and diabetes mellitus without systemic inflammation. In univariate analysis, survival at 30 days (p = 0.03) differed significantly between the low and high SAA concentration groups, but not at 180 days. In multivariate analysis, survival at 30 days did not significantly affect SAA concentration. Measurement of SAA concentration is a useful biomarker for detecting the presence or absence of inflammation in diseased cats. However, it may not be useful as a biomarker for determining the prognosis of the disease.

Diagnostic Criteria for Obesity Disease in Cats

Accumulated visceral and subcutaneous fat masses were measured with computed tomography (CT) in cats with various body condition scores (BCS) from 5/9 to 9/9. BCS does not always reflect visceral fat accumulation which induces pro-inflammatory reactions. Obese cats with accumulated visceral fat showed low plasma adiponectin and high serum amyloid A (SAA) concentrations, an inflammatory marker. Based on the above results, new diagnostic criteria for obesity disease were established as follows. For overweight cats with high BCS of >7/9, showing two or more of the following three symptoms, low adiponectin concentrations, hyperlipidemia, and high SAA concentrations, categorizes them as having obesity disease. Cats with BCS 6/9-9/9, without inflammatory reactions, were classified as simple obesity, which is similar to metabolically healthy obesity (MHO) defined in human medicine. Simple obesity group showed significantly higher adiponectin concentrations than those in control group. The obesity disease group showed significantly higher plasma triglyceride (TG) and SAA concentrations and lower concentrations of adiponectin than the control group. Moreover, plasma glucose and malondialdehyde (MDA) concentrations in the obesity disease group were higher than those in healthy control group, although the differences were not statistically significant. Establishing criteria for obesity disease based on visceral fat accumulation and inflammation markers levels contributes to early and correct diagnosis of obesity in cats.

The Immune Functions of α1 Acid Glycoprotein

α1-acid glycoprotein (orosomucoid, AGP) is an Acute Phase Protein produced by liver and peripheral tissues in response to systemic reaction to inflammation. AGP functions have been studied mostly in human, cattle and fish, although the protein has been also found in many mammalian species and birds. AGP fulfils at least two set of functions, which are apparently different from each other but in fact intimately linked. On one hand, AGP is an immunomodulatory protein. On the other hand, AGP is one of the most important binding proteins in plasma and, beside modulating pharmacokinetics and pharmacodynamics of many drugs, it is also able to bind and transport several endogen ligands related to inflammation. The focus of this review is the immunomodulatory activity of AGP. This protein regulates every single event related to inflammation, including binding of pathogens and modulating white blood cells activity throughout the entire leukocyte attacking sequence. The regulation of AGP activity is complex: the inflammation induces not only an increase in AGP serum concentration, but also a qualitative change in its carbohydrate moiety, generating a multitude of glycoforms, each of them with different, and sometimes opposite and contradictory, activities. We also present the most recent findings about the relationship between AGP and adipose tissue: AGP interacts with leptin receptor and, given its immunomodulatory function, it may be included among the potential players in the field of immunometabolism.

Acute phase proteins and biomarkers of oxidative status in feline spontaneous malignant mammary tumours

Acute phase proteins (APP) and biomarkers of oxidative status change in human and canine mammary tumours, however, they have not been studied in feline mammary tumours. The aims of this study were to investigate the APP and antioxidant responses in feline malignant mammary tumours, to evaluate their relation with tumour features, and to assess their prognostic value. Serum amyloid A (SAA), haptoglobin (Hp), albumin, butyrylcholinesterase (BChE), insulin-like growth factor1 (IGF1), paraoxonase1 (PON1), total serum thiols (Thiol), glutathione peroxidase (GPox) and total antioxidant capacity determined by different assays, including trolox equivalent antioxidant capacity assessed by two different methodologies (TEAC1/2), ferric reducing ability of plasma (FRAP), and cupric reducing antioxidant capacity (CUPRAC), were determined in serum of 50 queens with spontaneous mammary carcinomas and of 12 healthy female cats. At diagnosis, diseased queens presented significantly higher SAA and Hp, and lower albumin, BChE, GPox, TEAC1, TEAC2 and CUPRAC than controls. Different tumour features influenced concentrations of APP and antioxidants. Increases in serum Hp, and decreases in albumin, Thiol and FRAP were significantly associated with neoplastic vascular emboli, metastasis in regional lymph nodes and/or in distant organs. Distant metastasis development during the course of the disease was associated with increases in SAA and TEAC1. At diagnosis, decreased albumin was associated with a longer survival, and BChE <1.15 μmoL/mL.minute was associated with a shorter survival time on multivariate analysis. Feline malignant mammary tumours are associated with an APP response and oxidative stress, and different tumour features influence the inflammatory response and the oxidative damage. Furthermore, some of these analytes proved to have prognostic value.

Acute phase proteins and antioxidant responses in queens with pyometra

Acute phase proteins (APP) and biomarkers of oxidative status have proved to be clinically useful biomarkers of pyometra in different species. Despite pyometra is considered one of the most important feline reproductive diseases, information about the APP response and the oxidative status in queens with pyometra is lacking. This study aimed to evaluate the APP and the antioxidant responses at diagnosis and in the post-operative period in feline pyometra. Serum concentrations of serum amyloid A (SAA), haptoglobin (Hp), albumin, total serum thiols (Thiol) and total antioxidant capacity determined by different assays, including trolox equivalent antioxidant capacity (TEAC) assessed by two different methodologies (TEAC1 and TEAC2), ferric reducing ability of plasma (FRAP), and cupric reducing antioxidant capacity (CUPRAC), were determined in 23 queens with pyometra at diagnosis and in 13 healthy control queens submitted to elective ovariohysterectomy. The APP and antioxidants were also evaluated in 11 queens of the pyometra group at days two and 10 after surgery. At diagnosis, queens with pyometra had serum concentrations of SAA, Hp, and FRAP significantly higher (P < 0.001, P < 0.001 and P < 0.05, respectively), and of albumin, Thiol, CUPRAC and TEAC2 significantly lower (P < 0.001, P < 0.001, P < 0.001 and P < 0.01, respectively) than controls. Moreover, concentrations of APP and antioxidants were significantly different (with a tendency to return to physiologic levels) at day 10 after surgery than before surgery. Significant associations were found between APP and antioxidants. According to these results, an APP response and the development of oxidative stress were detected in queens with pyometra. In addition, APP and antioxidants tended to return to physiologic values after surgery in the queens that recovered from the disease. Therefore, our results suggest that APP and selected antioxidants, such as Thiol and CUPRAC, could be potentially useful biomarkers in diagnosis and assessment of the post-operative period in feline pyometra.

Acute phase proteins response in cats naturally infected by hemotropic mycoplasmas

Information about the acute phase proteins (APP) response in cats naturally infected with hemoplasmas and in cats co-infected with different species of hemoplasmas is lacking. This study evaluated serum amyloid A (SAA), haptoglobin (Hp) and albumin in 48 cats naturally infected with hemoplasmas, including 25 with Candidatus Mycoplasma haemominutum and 23 co-infected with different hemoplasmas agents; and in 10 healthy control cats. Infected cats had significantly higher Hp and lower albumin than controls. Symptomatic cats had significantly higher SAA and Hp, and lower albumin than asymptomatic animals, and also than controls. Asymptomatic cats had significantly higher Hp than controls. Concentrations of APP were not significantly different between single infected and co-infected cats. According with these results, hemoplasmosis should be considered when alterations in APP are detected in diseased cats with compatible clinical signs. Furthermore, a subclinical infection should be considered in apparently healthy cats from endemic areas with increased Hp.

Serum amyloid A in the diagnosis of feline sepsis

Systemic inflammatory response syndrome (SIRS) and sepsis can be challenging to diagnose in cats. Retrospectively, we investigated the diagnostic and prognostic potential of serum amyloid A (SAA), a major feline acute-phase protein (APP), in a population of critically ill cats with SIRS related to trauma or sepsis. A total of 56 SIRS cats (trauma n = 27; sepsis n = 29) were included and compared with healthy controls ( n = 18). SAA concentration was significantly increased in SIRS cats compared to controls, confirming its potential for the detection of systemic inflammation in this species. Significantly higher values of SAA were detected in cats belonging to the sepsis group; however, according to the results of the receiver operating characteristic curve analysis, the value of using SAA (>81 mg/L) to discriminate septic cats was only moderate (AUC = 0.76). Additionally, cats with sepsis had significantly higher serum bilirubin concentrations and toxic neutrophil changes compared to the trauma group. Overall, 38 of 56 cats were survivors; 18 of 56 were non-survivors, with 83% of the non-survivors (15 of 18) belonging to the sepsis group. Serum bilirubin concentration, but not SAA, was able to predict outcome. Prospective studies are needed to assess the potential of SAA in the diagnosis of feline sepsis and outcome prediction.

Acute-Phase Proteins and Iron Status in Cats with Chronic Kidney Disease

Background

The role of inflammation in the development and progression of chronic kidney disease (CKD) in cats is not well characterized. Hepcidin is a recently discovered acute‐phase protein (APP) that plays an important role in iron metabolism and contributes to the development of anemia in humans with CKD.

Objectives

To compare serum APP concentrations, iron status, and erythropoietin (EPO) concentrations in healthy cats and cats with naturally occurring CKD.

Animals

A total of 18 healthy control cats and 38 cats with CKD.

Methods

Prospective study. After complete physical examination and routine blood analysis, the following tests were performed: serum amyloid A (SAA), haptoglobin (HAP), EPO, serum iron and ferritin concentration as well as total iron‐binding capacity (TIBC). Serum hepcidin‐25 concentration was measured by ELISA kit designed for use in humans.

Results

Mean SAA and hepcidin concentrations were significantly higher and mean total iron and TIBC were significantly lower in the CKD group (P < .05). There was a significant positive correlation between serum creatinine concentration (CRT) and 2 of the APPs (SAA and hepcidin; P < .05). Increases in SAA and hepcidin were associated with decreases in TIBC and hematocrit in the CKD group. Fourteen (37%) of the cats with CKD were anemic, and these cats had significantly lower TIBC (P < .05), suggesting a functional iron deficiency. There was no association between survival time and APP, iron status, or EPO concentrations.

Conclusions

Our data suggest that CKD in cats is associated with systemic inflammation and altered iron metabolism. With further validation in cats, hepcidin assays may help better characterize these relationships.

Serum α-1 acid glycoprotein and serum amyloid A concentrations in cats receiving antineoplastic treatment for lymphoma

OBJECTIVE To characterize serum α-1 acid glycoprotein (AGP) and serum amyloid A (SAA) concentrations at diagnosis and during treatment in cats with lymphoma. ANIMALS 16 cats with various anatomic forms of lymphoma and 25 healthy cats. PROCEDURES Blood samples were collected from healthy cats once and from cats with lymphoma at diagnosis and 2-week intervals until the 12th week of antineoplastic treatment. Serum harvested from blood samples was assessed for AGP and SAA concentrations. Differences in serum AGP and SAA values were investigated between healthy cats and cats with lymphoma (at diagnosis) and, for cats with lymphoma, between diagnosis and various points during treatment. RESULTS Serum AGP and SAA concentrations were higher in cats with lymphoma at diagnosis (median, 832.60 and 1.03 μg/mL, respectively), compared with those in healthy cats (median, 269.85 and 0.10 μg/mL). Treatment resulted in a gradual decrease in serum AGP concentration after 4 weeks and in SAA concentration after 8 weeks of treatment, and these concentrations returned to values comparable with those of healthy cats by 12 weeks of treatment, by which point all cats had achieved complete remission of the disease. CONCLUSIONS AND CLINICAL RELEVANCE Serum AGP and SAA concentrations in cats with lymphoma were higher at diagnosis than after antineoplastic treatment. Decreases to values established for healthy cats corresponded with achievement of complete disease remission. Serum AGP and SAA may be useful protein markers for monitoring of antineoplastic treatment in cats with lymphoma.

Validation of an enzyme-linked immunosorbent assay for measurement of feline haptoglobin

Haptoglobin is a positive moderate acute phase protein (APP) in cats. Measurement of haptoglobin can be used in the diagnosis, prognosis, and monitoring of systemic inflammatory disease, especially by creating profiles with major APPs. The aim of our study was to validate a sandwich enzyme-linked immunosorbent assay (ELISA) for measurement of feline haptoglobin. The validation included an assessment of precision, accuracy, detection limit, method comparison with a spectrophotometric assay, and evaluation of the overlap performance. The concentration of haptoglobin was measured in serum from 27 healthy and 23 sick cats. The coefficients of variation were 2.5–4.7% for intra-assay variability and 7.1–11.6% for interassay variability. The ratio of observed to expected dilutional parallelism of 4 serum samples was 108.1–118.4%. The ratio of observed to expected spike recovery of 4 serum samples was 90.8–94.0%. The lower detection limit was 0.19 g/L. Method comparison revealed a positive correlation ( rs = 0.949, P < 0.0001) and a proportional bias between the methods of −38.9%. Agreement between the methods was not clinically acceptable. Overlap performance of the ELISA was deemed satisfactory. The sandwich ELISA measures feline haptoglobin with an analytical and overlap performance acceptable for clinical purposes. Given the observed bias, the ELISA cannot be used interchangeably with the spectrophotometric assay.

Serum Amyloid A Protein Concentration in Blood is Influenced by Genetic Differences in the Cheetah (Acinonyx jubatus)

Systemic amyloid A (AA) amyloidosis is a major cause of morbidity and mortality among captive cheetahs. The self-aggregating AA protein responsible for this disease is a byproduct of serum amyloid A (SAA) protein degradation. Transcriptional induction of the SAA1 gene is dependent on both C/EBPβ and NF-κB cis-acting elements within the promoter region. In cheetahs, 2 alleles exist for a single guanine nucleotide deletion in the putative NF-κB binding site. In this study, a novel genotyping assay was developed to screen for the alleles. The results show that the SAA1A (-97delG) allele is associated with decreased SAA protein concentrations in the serum of captive cheetahs (n = 58), suggesting genetic differences at this locus may be affecting AA amyloidosis prevalence. However, there was no significant difference in the frequency of the SAA1A (-97delG) allele between individuals confirmed AA amyloidosis positive versus AA amyloidosis negative at the time of necropsy (n = 48). Thus, even though there is evidence that having more copies of the SAA1A (-97delG) allele results in a potentially protective decrease in serum concentrations of SAA protein in captive cheetahs, genotype is not associated with this disease within the North American population. These results suggest that other factors are playing a more significant role in the pathogenesis of AA amyloidosis among captive cheetahs.

Association between feline immunodeficiency virus (FIV) plasma viral RNA load, concentration of acute phase proteins and disease severity

Veterinarians have few tools to predict the rate of disease progression in FIV-infected cats. In contrast, in HIV infection, plasma viral RNA load and acute phase protein concentrations are commonly used as predictors of disease progression. This study evaluated these predictors in cats naturally infected with FIV. In older cats (>5 years), log10 FIV RNA load was higher in the terminal stages of disease compared to the asymptomatic stage. There was a significant association between log10 FIV RNA load and both log10 serum amyloid A concentration and age in unwell FIV-infected cats. This study suggests that viral RNA load and serum amyloid A warrant further investigation as predictors of disease status and prognosis in FIV-infected cats.