Elien Taffin

Biological validation of feline serum cystatin C: The effect of breed, age and sex and establishment of a reference interval

Chronic kidney disease (CKD) is common in cats, but the routine renal markers, serum creatinine (sCr) and urea, are not sensitive or specific enough to detect early CKD. Serum cystatin C (sCysC) has advantages over sCr, both in humans and dogs, and sCysC concentration is significantly higher in cats with CKD than in healthy cats. The objective of this study was to determine the effect of age, sex and breed on feline sCysC and to establish a reference interval for feline sCysC. In total, 130 healthy cats aged 1-16 years were included. sCysC was determined using a validated particle-enhanced nephelometric immunoassay. sCr, urea, urine specific gravity, urinary protein:creatinine ratio (UPC) and systolic blood pressure (SBP) were also measured. No significant differences in sCysC concentration were observed among young, middle-aged and geriatric cats, female intact, female neutered cats, male intact and male neutered cats, or among purebred and domestic short-or longhaired cats. The 95% reference interval for feline sCysC was determined to be 0.58-1.95 mg/L. sCr was significantly higher in geriatric cats than young cats. Serum urea in geriatric cats was significantly higher than in middle-aged and young cats (P = 0.004 and P <0.001, respectively). SBP in geriatric cats was significantly higher than in both middle-aged and young cats (P = 0.004 and P = 0.040, respectively). Male neutered and female neutered cats had significantly higher serum urea concentrations than female intact cats (P = 0.003 and P = 0.006, respectively). Male intact cats had a significantly higher UPC than female intact and female neutered cats (P = 0.02 for each comparison). There were no significant differences among sex groups for USG. It is of concern that sCysC in the majority of cats with CKD in previous studies falls within the reference interval calculated in this study. Further studies are warranted to evaluate the diagnostic value of sCysC as a renal marker in cats.

Serum and urinary cystatin C in cats with feline immunodeficiency virus infection and cats with hyperthyroidism.

Objectives The objective of this study was to investigate serum cystatin C (sCysC) and urinary cystatin C (uCysC) in cats with hyperthyroidism and cats with feline immunodeficiency virus (FIV). Methods Thirty cats with FIV, 26 hyperthyroid cats and 28 healthy cats were included. sCysC and uCysC:creatinine (uCysC/uCr) ratio were measured with a human particle-enhanced nephelometric immunoassay, previously validated for feline CysC measurement. Routine renal variables (serum creatinine [sCr], urine specific gravity, urinary protein:creatinine ratio [UPC]) were also measured in the three groups. Results Cats with hyperthyroidism had significantly higher sCysC and higher uCysC/uCr ratio, lower sCr and a higher UPC than healthy cats. Cats with FIV infection did not show a significantly higher sCysC concentration but had a significantly higher sCr and UPC than healthy cats. uCysC could be detected in only four of them. Conclusions and relevance This study demonstrated that sCysC is increased in cats with hyperthyroidism, in contrast with sCr, but not in cats with FIV. Many hyperthyroid cats, but only four cats with FIV, had an elevated uCysC/uCr ratio. Further studies may reveal if uCysC might be a valuable marker for tubular dysfunction in cats.

Antiviral treatment of feline immunodeficiency virus-infected cats with (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine.

Feline immunodeficiency virus (FIV), the causative agent of an acquired immunodeficiency syndrome in cats (feline AIDS), is a ubiquitous health threat to the domestic and feral cat population, also triggering disease in wild animals. No registered antiviral compounds are currently available to treat FIV-infected cats. Several human antiviral drugs have been used experimentally in cats, but not without the development of serious adverse effects. Here we report on the treatment of six naturally FIV-infected cats, suffering from moderate to severe disease, with the antiretroviral compound (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine ([R]-PMPDAP), a close analogue of tenofovir, a widely prescribed anti-HIV drug in human medicine. An improvement in the average Karnofsky score (pretreatment 33.2 ± 9.4%, post-treatment 65±12.3%), some laboratory parameters (ie, serum amyloid A and gammaglobulins) and a decrease of FIV viral load in plasma were noted in most cats. The role of concurrent medication in ameliorating the Karnofsky score, as well as the possible development of haematological side effects, are discussed. Side effects, when noted, appeared mild and reversible upon cessation of treatment. Although strong conclusions cannot be drawn owing to the small number of patients and lack of a placebo-treated control group, the activity of (R)-PMPDAP, as observed here, warrants further investigation.

The effect of feeding, storage and anticoagulant on feline serum cystatin C

Serum cystatin C (sCysC) is a possible marker for early detection of chronic kidney disease (CKD) in cats. In contrast with serum creatinine (sCr), feline sCysC is not affected by age, breed or sex. However, further biological and clinical validation is required. The objectives of this study were: (1) to investigate if food intake and circadian rhythm affect feline sCysC; (2) to determine the stability of sCysC under different storage conditions, and (3) to investigate if plasma concentrations of CysC (pCysC) differed from sCysC. A crossover study with 10 healthy laboratory cats fed the same commercial dry food was performed to study the influence of feeding and diurnal variation. Storage effects and comparison of pCysC with sCysC were determined using healthy cats (n = 3 and n = 10, respectively) and cats with CKD (n= 4 and n = 17, respectively). A significant daily sCysC variation was seen. Pre- and postprandial sCysC and sCr concentrations did not change significantly. Serum CysC significantly increased during storage at room temperature. After freezing, sCysC significantly decreased after 5 and 12 months at both -20 °C and -72 °C. Plasma CysC was significantly lower than sCysC. These findings suggest that it is not mandatory to fast cats before evaluation of sCysC and sCr. Samples were stable during routinely used storage conditions. Based on these findings, freezing for more than 5 months is not recommended, although additional studies are required to evaluate the clinical relevance of decreased sCysC after prolonged storage. Plasma and serum CysC cannot be compared directly.

Evaluation of a modified Karnofsky score to assess physical and psychological wellbeing of cats in a hospital setting

Objectives The Karnofsky score (KS) modified for cats, a scoring system to rate health and quality of life (QOL) in cats, is used in clinical trials, but its reliability and validity are yet to be determined. The present study aims to evaluate the scientific robustness of the KS when adapted for use in a hospital setting. Methods A list of variables to consider during the physical examination, which informs the clinician’s score (CS) part of the KS, was added and clinicians were allowed to choose a score anywhere between 0 and 50. The Karnofsky QOL questionnaire was adapted for use in a hospital setting. F-tests with Bonferroni correction and Spearman rank correlation coefficients were used to evaluate reliability and validity of the KS to assess the health and wellbeing of cats in a hospital setting. The records of 54 feline immunodeficiency virus-positive cats, which were recruited for a clinical trial and hospitalised for 6 weeks, were reviewed. Four veterinarians scored the CS, and one veterinarian and a veterinary nurse assessed the QOL score. Results Mean absolute difference between observers was significantly larger for the CS than for the QOL score (P <0.001) and two veterinarians scored significantly higher than the remaining two veterinarians (P <0.001). Inter-observer correlation ranged from 0.45–0.75 for the CS. For the QOL score, the absolute difference between observers was small, no significant difference was found between observers and a high degree of inter-observer correlation was noted (r = 0.91). Conclusions and relevance The results indicate low inter-observer reliability for the CS, requiring additional modifications to this part of the KS. The QOL score seems more reliable, and the questionnaire may serve as a reliable tool in the assessment of QOL in cats in a hospital setting. Consequently, further adaptation of the KS is mandatory when simultaneous assessment of both the cat’s clinical health and perceived wellbeing is required.

Systolic blood pressure, routine kidney variables and renal ultrasonographic findings in cats naturally infected with feline immunodeficiency virus

Objectives Hypertension is a common cause of proteinuria in HIV-infected people. In cats, feline immunodeficiency virus (FIV) infection appears to be associated with proteinuria. Therefore, the results from systolic blood pressure (SBP) measurements in naturally infected FIV-positive cats were reviewed to assess whether hypertension contributes to the observed proteinuria in these cats. Ultrasonographic findings in FIV-positive cats were reviewed to complete renal assessment and to extend the scant knowledge on renal ultrasonography in cats. Methods Data from client-owned, naturally infected FIV-positive cats were retrospectively reviewed. To obtain a control group, records were reviewed from age-matched, privately owned, FIV-negative cats. Results Data from 91 FIV-infected and 113 control cats were compared. FIV-infected cats showed a significantly lower SBP (P <0.0001) and significantly fewer FIV-infected cats were hypertensive (⩾160 mmHg) compared with control cats (P = 0.025). The prevalence of renal azotaemia did not significantly differ between groups, although FIV-infected cats had significantly lower urine specific gravity (USG) (P = 0.0273) and a higher incidence of USG below 1.035 (P = 0.043). Urinary protein:creatinine ratio (UPC) was significantly higher in FIV-infected cats (P = 0.0005) and proteinuria (UPC >0.4) occurred more frequently in FIV-infected cats (P <0.001). Renal ultrasonography showed abnormalities in 60/91 FIV-infected cats, with hyperechogenic cortices in 39/91 and enlarged kidneys in 31/91. Conclusions and relevance Hypertension can be excluded as a common cause of renal damage leading to proteinuria in FIV-infected cats. Proteinuria and poorly concentrated urine are common in naturally infected FIV-positive cats, in contrast to azotaemia. Clinicians should cautiously interpret ultrasonographic abnormalities as these occur in over half of FIV-infected cats.

Phylogenetic analysis of feline immunodeficiency virus strains from naturally infected cats in Belgium and The Netherlands.

Feline immunodeficiency virus (FIV) is a major pathogen in feline populations worldwide, with seroprevalences up to 26%. Virus strains circulating in domestic cats are subdivided into different phylogenetic clades (A-E), based on the genetic diversity of the V3-V4 region of the env gene. In this report, a phylogenetic analysis of the V3-V4 env region, and a variable region in the gag gene was made for 36 FIV strains isolated in Belgium and The Netherlands. All newly generated gag sequences clustered together with previously known clade A FIV viruses, confirming the dominance of clade A viruses in Northern Europe. The same was true for the obtained env sequences, with only one sample of an unknown env subtype. Overall, the genetic diversity of FIV strains sequenced in this report was low. This indicates a relatively recent introduction of FIV in Belgium and The Netherlands. However, the sample with an unknown env subtype indicates that new introductions of FIV from unknown origin do occur and this will likely increase genetic variability in time.