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Determination of serum fPLI concentrations in cats with diabetes mellitus
Journal of Feline Medicine and Surgery (2008) 10, 480e487 doi:10.1016/j.jfms.2007.04.007
Determination of serum fPLI concentrations in cats with diabetes mellitus Yaiza Forcada DVM, MRCVS1*, Alexander J German BVSc, PhD, Dip ECVIM-CA, CertSAM, MRCVS1, Peter JM Noble BSc, BVM&S, PhD, MRCVS1, Joerg M Steiner Med Vet, Dr Med Vet, PhD, Dip ECVIM-CA, 2 2 DACVIM , Jan S Suchodolski Med Vet, Dr Med Vet, PhD , Peter Graham BVMS, PhD, CertVR, 3 1 DipECVCP, MRCVS , Laura Blackwood BVMS, PhD, MVM, CertVR, Dip ECVIM-CA (Onc), MRCVS 1 Department of Veterinary Clinical Science, University of Liverpool, Leahurst, UK 2 Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, Texas A&M University, 4474 TAMU, College Station, TX, USA 3 Nationwide Laboratories, Poulton le Fylde, UK
Date accepted: 23 April 2007
Diabetes mellitus (DM) is one of the most common feline endocrinopathies. Pancreatitis is a reported cause for poor control of DM in cats; however, its prevalence in diabetic cats is unknown. Measurement of serum feline pancreatic lipase immunoreactivity (fPLI) has been proposed as a sensitive and specific test for the detection of pancreatitis in cats. The aim of this study was to assess fPLI concentrations in diabetic cats and compare these with non-diabetic cats of similar age. Samples from 29 cats with DM and 23 non-diabetic cats were analysed. Serum fPLI concentrations were significantly higher in samples from diabetic cats (P < 0.01). A weak association was found between serum fructosamine and fPLI concentrations (R2 ¼ 0.355, P ¼ 0.015), but there was no association between fPLI concentrations and the degree of diabetic control. There were no significant differences in reported clinical signs between cats with or without DM regardless of serum fPLI concentration. This is the first study to demonstrate elevated serum fPLI concentrations in cats with DM, suggesting that pancreatitis could be a significant comorbidity in these cats. Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.
D
iabetes mellitus (DM) is one of the most common endocrinopathies in cats. The prevalence of DM in cats has been reported in several studies from different countries and differs substantially amongst studies; geographical variation could, in part, account for these differences (Panciera et al 1990, Baral et al 2003, Rand et al 2004, Prahl et al 2007). The incidence of this disease appears to be increasing, most likely due to changes in the life-style of the feline population (Prahl et al 2003, McCann et al 2007, Slingerland et al 2007). The most common form of DM in cats resembles human type 2 DM, and was initially also called non-insulin dependent DM (NIDDM). In contrast to type 1 DM, where there is an absence of insulin production, type 2 DM is characterised by insufficient insulin secretion in conjunction with impaired insulin action or insulin resistance (Rand 1999). The increased demand on the b cells *Corresponding author. E-mail: [email protected]
1098-612X/08/050480+08 $34.00/0
to produce more insulin in the presence of insulin resistance is suggested to lead to b cell damage and ultimately cell death. Other causes that can induce death of pancreatic b cells include amyloid deposition, glucose toxicity, pancreatitis or dietary factors (Rand 1999). Pancreatitis seems to be an emerging disease in cats, largely due to the fact that its prevalence was previously under-estimated. In contrast to dogs and humans where the disease is rather well-defined clinically, feline pancreatitis is less well understood. Clinical signs and serum biochemical changes are often non-specific and, therefore, the diagnosis is challenging (Zoran 2006). Traditionally, diagnostic investigations included measurement of pancreatic enzymes, diagnostic imaging and pancreatic biopsy. However, more recently, non-invasive diagnosis of feline pancreatitis has been facilitated by the development of a species-specific assay for the measurement of feline pancreatic lipase immunoreactivity (fPLI) concentration in serum.
Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.
Determination of serum fPLI concentrations in cats with DM
Pancreatitis (and particularly chronic pancreatitis) has been cited as a possible cause of poor diabetic control in feline patients with DM (Goossens et al 1998, Feldman and Nelson 2004, Nelson 2005). However, there have been no previous reports assessing the prevalence of pancreatitis in a population of live diabetic cats. The aims of this study were to determine whether serum fPLI concentration was higher in cats with DM, whether serum fPLI concentrations are linked to diabetic control, and whether these cats have any specific clinical signs of pancreatitis.
Materials and methods Study subjects and samples
Serum samples from cats submitted to Nationwide Laboratories (Poulton le Fylde, UK) between November 2006 and February 2007 were used in the study. Samples came from two populations of cats. The first comprised samples from diabetic cats, where serum had been submitted for fructosamine determination. Inclusion criteria were adequate residual volume for fPLI assay, and presence of DM for at least 1 month prior to sampling. A nondiabetic population was generated from surplus serum samples submitted to the same laboratory within a similar time-frame. An attempt was made to include samples with similar signalment to the diabetic cats. Cats with evidence of either hyperthyroidism or hypoalbuminaemia were excluded from the study, because of possible effects on serum fructosamine concentration. Samples that were visibly lipaemic or haemolysed were not included in the study, due to the potential effects of these on the fructosamine and fPLI results. For the fPLI assay, all samples were batched and transported to the Gastrointestinal (GI) Laboratory, Texas A&M University, in a frozen state and on dry ice. fPLI
Serum fPLI was measured by an in-house radioimmunoassay, at the GI Laboratory, Texas A&M University, using the method previously described (Steiner et al 2004). All samples were submitted frozen, coded before analysis, and then analysed in a blinded fashion in a single batch in order to avoid artefactual changes due to inter-assay variability. The previously established reference range for serum fPLI concentration was 2.0e6.8 mg/l, with concentrations
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>12 mg/l being considered indicative of pancreatic inflammation (Steiner 2006). Other assays
Serum fructosamine concentrations were measured by Nationwide Laboratories (Poulton le Fylde, UK) using a colorimetric assay (Cobas Fructosamine assay, Roche, Germany) previously validated for use in cats (Reusch et al 1993, Thoresen and Bredal 1995, Crenshaw et al 1996, Graham et al 1999). The laboratory’s reference interval for serum fructosamine was 146e 271 mmol/l. This was internally established and verified by analysing samples from a population of healthy non-diabetic cats. For the purpose of the study, fructosamine was also determined in the serum of 23 non-diabetic cats to support the validity of this reference range. In the diabetic patients, concentrations of fructosamine <500 mmol/l were considered to represent good diabetic control, whilst those with fructosamine concentrations >500 mmol/l were considered to be evidence for poor control (Feldman and Nelson 2004). When adequate residual plasma volume was available, serum albumin concentrations and either total T4 or free T4 (by equilibrium dialysis) were also assayed by Nationwide Laboratories. Total T4 was measured in 21 of 29 diabetic cats and 20 of 23 non-diabetic cats; free T4 was measured in one of 29 diabetic cats. Confirmed hyperthyroid cats were not included in the study. Serum albumin concentrations were measured in all samples. Questionnaires
Questionnaires were sent to the referring veterinary surgeons of all of cats in the study, in order to acquire information about their clinical signs. The questions were the same for both populations, with the exception of questions about the insulin regime in the diabetic population (Table 1). Given the fact that the non-diabetic population had a higher number of female cats and in order to avoid misinterpretation of results with regards to body mass, the attending veterinary surgeons were asked to provide body condition score (BCS) (Laflamme 1997) instead of body weight. If questionnaires were not returned within 8 weeks, the referring veterinary surgeons were contacted by phone and then again by post. To maximise the return rate, each veterinary surgeon who did not reply initially was contacted a total of three times.
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Table 1. Summary of the results obtained in a questionnaire submitted to the veterinary surgeons responsible for the care of 29 diabetic and 23 non-diabetic cats Diabetic population
Non-diabetic population
fPLI levels (mg/l)
12
12e20
20e50
50
12
12e20
20e50
Fructosamine > 500 mmol/l Fructosamine < 500 mmol/l Overweight (BCS > 5/9) Normal weight (BCS: 5/9) Underweight (BCS < 5/9) Weight loss
1/2 1/2 1/2 1/2 0/2 0/2
3/6 3/6 4/6 1/6 1/6 2/6
5/9 4/9 5/9 2/9 2/9 5/9
3/5 2/5 0/5 3/5 2/5 3/5
0/5 5/5 1/5 1/5 3/5 3/5
0/3 3/3 0/3 0/3 3/3 2/3
0/6 6/6 2/6 0/6 4/6 4/6
Subtotal
2
6
9
5
5
3
6
Total
22
Statistical analysis
Statistical analyses were performed with a computer software package (Minitab v14.0; Minitab Inc), and non-parametric tests were used throughout. ManneWhitney tests were used to compare differences of median serum fPLI concentrations between the cats with and without DM. The diabetic group was further subdivided into two groups; cats with good control and those with poor control of DM, as determined by measurement of serum fructosamine concentration (fructosamine concentrations <500 mmol/l were used as evidence for good control and fructosamine concentrations >500 mmol/l were used as evidence for poor control) (Feldman and Nelson 2004). Once again, ManneWhitney tests were used to compare these groups. Associations between continuous data were assessed by Spearman’s correlation, whilst c2 analysis or Fisher’s exact test (as appropriate) was used to assess differences in presence of weight loss between groups (based on questionnaire data). Differences were considered significant when P < 0.05.
Results A total of 52 serum samples were included in the study, 29 from diabetic cats and 23 from nondiabetic cats. Diabetic population
Of the 29 samples from diabetic cats, 25 were from domestic shorthair (DSH) cats , whilst the remaining samples were from domestic longhair (DLH; n ¼ 2) cats, or from cats of unknown breeds (n ¼ 2). The median age of the diabetic
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population was 12 years (range: 4e18 years). Twenty of the samples were from male cats (16 of which were neutered), seven were from female cats (six neutered) and two were of unknown gender. Non-diabetic population
Of the 23 samples, 17 were from DSH cats, whilst the remainder was from Persian cats (n ¼ 2), DLH cats (n ¼ 2), Birman (n ¼ 1) and one from a cat of an unknown breed. The median age was 13.5 years (range: 8e21 years). Eleven of the samples were from male cats (10 of which were neutered), 11 of the samples were from female cats (10 of which were neutered), and one was from a cat of unknown gender. The median age of the cats in this group was significantly higher than that of diabetic cats (ManneWhitney test, P ¼ 0.008). Fructosamine
Median serum fructosamine concentration was significantly higher in the diabetic population than in non-diabetic cats (ManneWhitney test, P ¼ 0.001; Fig 1). The median fructosamine concentration for diabetic cats was 514 mmol/l (range: 241e782 mmol/l). Sixteen of the diabetic cats had serum fructosamine concentrations indicative of poor control (fructosamine > 500 m mol/l); 12 cats had fructosamine concentrations suggestive of good control (fructosamine < 500 m mol/l) and one had fructosamine concentrations suggestive of periods of hypoglycaemia (241 mmol/l). In the non-diabetic group, the median fructosamine concentration was 238 mmol/l (range: 188e290 mmol/l). One of these cats had a fructosamine concentration of 290 mmol/l,
Determination of serum fPLI concentrations in cats with DM
Fig 1. Box and whiskers plot diagram showing serum fructosamine concentration in the 23 non-diabetic cats and the 29 diabetic cats. The box represents 50% of the population, with the horizontal bar within the box being the median. The whiskers represent the range of fructosamine concentrations for each population and the dots in the figure are outlying values. The median fructosamine concentration was significantly higher in diabetics than in control cats (P ¼ 0.001).
which was marginally above the reference interval from the laboratory (146e271 mmol/l); however, none had fructosamine concentrations that were elevated to a level suggestive of DM or insulin resistance. Fructosamine concentrations were negatively correlated with age (Spearman’s correlation [Rs ¼ 0.404, P ¼ 0.001]). fPLI
The median serum fPLI concentration was higher in diabetic patients (median: 22.5 mg/l, range: 8.1e283.5 mg/l) than in the non-diabetic population (median: 13.8 mg/l, range: 4.6e33.4 mg/l; ManneWhitney test, P < 0.01; Fig 2). No association was found between age and fPLI (Spearman’s correlation [Rs ¼ 0.110, P ¼ 0.468]). No difference in fPLI was found between the four different genders (male, male neutered, female and female neutered) ((KruskaleWallis test,
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Fig 2. Box and whiskers plot diagram showing serum fPLI concentration in the 23 non-diabetic cats and the 29 diabetic cats. The box represents the 50% of the population with the horizontal bar within the box being the median. The whiskers represent the range of fPLI concentration and the dots are outlining values. The median serum fPLI concentration was higher in diabetic patients (median: 22.5 mg/l, range: 8.1e283.5 mg/l) than in the control population (median: 13.8 mg/l, range: 4.6e33.4 mg/l; ManneWhitney test, P < 0.01).
P ¼ 0.786), or when comparing male vs female (regardless of neutering status) Manne Whitney test, P ¼ 0.235). A weak association was noted between serum fructosamine and fPLI concentrations (R2 ¼ 0.355, P ¼ 0.015; Fig 3). However, there was no significant difference in the median serum fPLI concentration between cats considered to have good diabetic control compared to those that had poor diabetic control, as defined by a fructosamine concentration <500 mmol/l or >500 mmol/l, respectively. Based on fPLI concentrations, 24 of 29 (83%) diabetic cats and 15 of 23 (66%) non-diabetic cats had fPLI concentrations which would be suggestive of the presence of pancreatic inflammation (Steiner 2006). Within the diabetic group, five cats had markedly increased fPLI concentrations (>50 mg/l), 11 cats had moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), eight
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Fig 3. Correlation between serum fructosamine and fPLI concentrations in 29 diabetic cats. A weak association was noted between serum fructosamine and fPLI concentrations (Rs ¼ 0.355, P ¼ 0.015). However, there was no significant difference of the median serum fPLI concentration between cats considered to have good diabetic control vs those that had poor diabetic control.
cats had mildly elevated concentrations (fPLI: 12e20 mg/l), and five cats had fPLI concentrations not indicative of pancreatic inflammation (fPLI < 12 mg/l). Within the non-diabetic group, no cats had markedly elevated fPLI concentrations, eight cats had moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), seven cats had mildly elevated concentrations (fPLI: 12e20 mg/l) and eight cats had fPLI concentrations not indicative of pancreatic inflammation (fPLI < 12 mg/l). Questionnaires (Table 1)
A total of 22 questionnaires were received from veterinarians of the group of 29 diabetic cats. None of these cats had vomiting, diarrhoea or abdominal pain. Questionnaires were received from all five diabetic cats with markedly elevated fPLI concentrations (>50 mg/l); four of these five were considered by the attending clinician to have poor control of their DM. Three of these cats had fructosamine concentrations suggestive of poor control of the diabetes (fructosamine concentration > 500 mmol/l); the remaining two cats had fructosamine concentrations suggestive of good control. Three of these five cats had evidence of weight loss.
Nine questionnaires were returned from the group of 11 diabetic cats with moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), five of these cats were considered to have good diabetic control by the attending clinician, whereas four of them were considered to have poor control. Five of these nine cats had weight loss. Six of these cats had fructosamine concentrations suggestive of poor control of their DM (fructosamine > 500 mmol/l). One had fructosamine levels suggestive of periods of hypoglycaemia (fructosamine < 300 mmol/l). The two remaining cats had fructosamine levels suggestive of good diabetic control. Five of these nine cats were overweight. Seven questionnaires were received from the veterinary surgeons of the nine diabetic cats with mildly elevated fPLI concentrations (fPLI: 12e20 mg/l). Four of these cats had fructosamine concentrations that suggested poor diabetic control (500 mmol/l). The three remaining cats had fructosamine levels indicative of good control and the veterinary surgeons of two of these three cats considered the control to be good. Five of these seven cats were overweight. Only one questionnaire was received regarding the five cats with normal fPLI concentrations. On this cat, the diabetic control was good according to the clinical assessment but poor according to fructosamine concentration. Fourteen questionnaires were received regarding the non-diabetic cats. Six questionnaires were received from the veterinary surgeons of the eight non-diabetic cats with moderately elevated fPLI concentrations (fPLI: 20e50 mg/l). Four cats were reported to be losing weight, and their BCS indicated that they were underweight. However, two of these cats were also reported to have concurrent chronic kidney disease. Three questionnaires were received regarding the seven non-diabetic cats with mildly elevated fPLI concentrations (fPLI: 12e20 mg/l). Two cats were reported to have weight loss and were underweight according to BCS. Five questionnaires were returned from veterinary surgeons regarding the eight non-diabetic cats with normal fPLI concentrations. One cat was underweight (BCS: 2/9), had diarrhoea and was on treatment with a depot-steroid preparation for suspected inflammatory bowel disease. A second cat was also underweight (BCS: 3/9) and was reported to have renal and hepatic disease, as well as mammary gland carcinoma. One further cat also had weight loss but
Determination of serum fPLI concentrations in cats with DM
no underlying disorder had been identified by the referring veterinary surgeon. Median BCS was significantly higher in cats with DM than in the non-diabetic cats (Manne Whitney test, P ¼ 0.003). This effect was due both to there being more overweight cats in the diabetic group and more underweight cats in the non-diabetic population (c2 analysis, P < 0.001). There were no other significant differences in the clinical signs between diabetic and non-diabetic cats. Furthermore, no significant differences were noted, for any of the assessed parameters, between cats with abnormal PLI results and those where PLI was normal.
Discussion The study has examined fPLI concentrations in diabetic and non-diabetic cats. Median serum fPLI concentration was significantly higher in the diabetic population, which suggest that pancreatic inflammation may be more prevalent in diabetic cats than in non-diabetic cats. Pancreatitis has previously been mentioned as a cause for DM and poor diabetic control in cats (Goossens et al 1998, Rand et al 2004, Feldman and Nelson 2004, Nelson 2005). It is of note that the three highest fPLI concentrations came from diabetic cats, and the degree of elevation in these cases would be suggestive of severe pancreatitis (Forman et al 2004). A major study limitation was the fact that the finding of increased fPLI implies, but does not confirm, the presence of pancreatic inflammation. Although this is the most likely explanation, there may be other explanations. In this respect, it may be that the diabetic state affects the metabolism of fPLI, or that inter-current pancreatic or nonpancreatic conditions (such as hepatic or renal disease) could affect the metabolism and clearance of fPLI and, therefore, the results of the study. Further, it is possible that other types of pancreatic pathology (eg, pancreatic neoplasia, necrosis or trauma) might also cause increases in fPLI concentration. Therefore, further work would be required to determine the exact reason for elevated fPLI concentrations in the diabetic cats in this study. A second study limitation was the fact that it made use of retrospective data acquired from cats where a sample had been submitted to a commercial laboratory. Thus, the clinical management amongst cats was likely to be variable and clinical information was lacking for some of the study subjects. It also meant
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that neither pancreatic histopathology nor abdominal ultrasonography were available to support the diagnosis of pancreatitis in these cats. The availability of these tests for the study subjects could have helped to provide further support in connecting fPLI elevations with pancreatitis in these cats. Nonetheless, fPLI is reported to be a moderately sensitive (67% in cats with pancreatic pathology) and highly specific (91% in cats without pancreatic pathology) test for pancreatitis (Forman et al 2004); therefore, although it is not possible to conclude that the diabetic cats on this study with high fPLI concentrations were suffering from pancreatitis, this is still the most likely reason. A further limitation of the current study was the fact that the non-diabetic population was significantly older than the diabetic population, and included a greater number of female cats. However, given that there was no significant effect of age on fPLI concentrations, this problem has unlikely affected the findings and conclusions of the study. Further, there was no significant effect of gender on fPLI concentrations, suggesting that differences in the number of female and male cats would not have accounted for the results obtained. The fact that fructosamine concentrations were negatively correlated with age was most likely due to the fact that the non-diabetic population was significantly older than the diabetic group. Moreover, although body weight was likely to have been different between the two groups (because male cats are usually heavier than female cats), this would not have accounted for the differences in body condition, a recognised 9-point system was used for this purpose (Laflamme 1997). A final concern was the fact that hyperthyroidism could not be excluded in a minority of the patients. This could have affected fructosamine or fPLI values. However, there is currently no evidence to suggest that hyperthyroidism affects fPLI values, contrary to what happens with fructosamine (Graham et al 1999). As samples of both groups were handled under the same conditions and analysed as a single batch, dehydration during storage in a frozen state is unlikely to have accounted for differences in fPLI concentrations between these groups. Despite the limitations of the study, the association between elevated fPLI concentrations and the presence of DM is of interest. To explore a possible link with pancreatitis, a questionnaire survey was performed. The responses suggested that all five cats with severely elevated fPLI
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concentrations (>50 mg/l) had been diagnosed with DM for less than 1 year; three of them had weight loss and, according to the clinical signs, the referring veterinary surgeons considered that their diabetic control was poor. Although one of the other two cats was not considered to be underweight by the veterinary surgeon, its body weight was 3.4 kg, which may in fact be low for a neutered male DSH cat. Although severe pancreatitis could have been a cause for weight loss in these three cases, the number of cases is too small to allow statistical assessment. In fact, the weight loss could also have been attributed to poor diabetic control or to the presence of a concurrent disease other than pancreatitis. Nonetheless, it is of note that weight loss was not a feature of the cats with poor diabetic control, but without evidence of pancreatitis, as based on serum fPLI concentration. As expected, median serum fructosamine concentration was significantly higher in diabetic cats than in non-diabetic cats. However, there was not always a clear association between the clinical judgement of diabetic control as specified by the referring veterinarian and serum fructosamine concentrations. Serum fructosamine concentrations consistent with good diabetic control may also be seen in patients that have had periods of both hyperand hypoglycaemia over the preceding weeks due to poor control of DM; this scenario could also occur in the presence of another concurrent disease other than DM that causes similar clinical signs but does not affect fructosamine concentration. Amongst the 14 questionnaires received regarding the cats with moderate and severe elevations of fPLI (fPLI > 20 mg/l) there were four cats for which the fructosamine concentrations were suggestive of good control, but the clinical impression of the attending clinician was that the diabetes was poorly controlled. This might indicate that pancreatitis could be a clinically significant complicating factor in a proportion of diabetic cats, even in those cases in which the fructosamine concentration indicates good control of the diabetes. However, other causes for poor correlation of the clinical signs as perceived by the veterinary surgeons and the fructosamine levels cannot be excluded. As cats with DM are generally middle-aged to old, concurrent diseases other than pancreatitis could also be contributing to the overall clinical picture and could be causing elevations of fPLI.
Currently, pancreatic histopathology is considered to be the gold standard for the diagnosis of pancreatitis in cats. For obvious reasons, this was not available in the cases studied; however, it is important to be aware of the limitations of histopathology, mainly due to the patchy distribution of pancreatic inflammation. A previous study, in which pancreatic histopathology was performed on post-mortem examination of non-diabetic cats, revealed the presence of pancreatitis in 67% of the population examined; this population consisted of cats of both sexes and different breeds with age ranging from 3 months to 21 years and which had died or been euthanased for numerous different problems, including trauma, neoplasia, gastrointestinal tract problems and cardiovascular problems. Forty-five percent of these cats were reported to be clinically normal before they died (De Cock et al 2007). The prevalence of pancreatitis in the study by De Cock et al (2007) was similar to the prevalence of fPLI elevation found in our non-diabetic population. However, the prevalence of fPLI elevation found in diabetic cats in this study was 82%, which is markedly higher than in the population of cats described by De Cock et al (2007). The prevalence of pancreatitis in diabetic cats has, to the knowledge of the authors, only been reported in one previous study in which pancreatic histopathology was performed postmortem in several diabetic Burmese and nonBurmese cats (Lederer et al 2004). In that study, histological evidence of pancreatitis was found in 47% of diabetic non-Burmese cats and in 11% of diabetic Burmese cats. The use of canine PLI (cPLI) was also reported in 40 newly diagnosed diabetic dogs and, on the basis of these results, the prevalence of pancreatitis in diabetic dogs was considered to be 16% (Davidson et al 2003). Furthermore, other studies report that chronic pancreatitis is the cause for DM in dogs in up to 28% of cases (Rand et al 2004). In summary, the findings of this study suggest that fPLI concentrations are higher in diabetic cats when compared to a population of nondiabetic cats. These elevations could represent pancreatitis, although other reasons for the increased fPLI concentrations are possible. Further studies are warranted to assess the influence of pancreatitis in control, progression and management of DM and to clarify the influence of diabetes and other diseases on the metabolism and clearance of fPLI.
Determination of serum fPLI concentrations in cats with DM
Acknowledgements YF is currently undertaking a residency sponsored by the Feline Advisory Bureau. Alexander James German’s senior lectureship is funded by Royal Canin. We would also like to thank the staff at Nationwide Laboratories for their help with the samples and the referring veterinary surgeons who completed the questionnaires.
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Determination of serum fPLI concentrations in cats with diabetes mellitus Yaiza Forcada DVM, MRCVS1*, Alexander J German BVSc, PhD, Dip ECVIM-CA, CertSAM, MRCVS1, Peter JM Noble BSc, BVM&S, PhD, MRCVS1, Joerg M Steiner Med Vet, Dr Med Vet, PhD, Dip ECVIM-CA, 2 2 DACVIM , Jan S Suchodolski Med Vet, Dr Med Vet, PhD , Peter Graham BVMS, PhD, CertVR, 3 1 DipECVCP, MRCVS , Laura Blackwood BVMS, PhD, MVM, CertVR, Dip ECVIM-CA (Onc), MRCVS 1 Department of Veterinary Clinical Science, University of Liverpool, Leahurst, UK 2 Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, Texas A&M University, 4474 TAMU, College Station, TX, USA 3 Nationwide Laboratories, Poulton le Fylde, UK
Date accepted: 23 April 2007
Diabetes mellitus (DM) is one of the most common feline endocrinopathies. Pancreatitis is a reported cause for poor control of DM in cats; however, its prevalence in diabetic cats is unknown. Measurement of serum feline pancreatic lipase immunoreactivity (fPLI) has been proposed as a sensitive and specific test for the detection of pancreatitis in cats. The aim of this study was to assess fPLI concentrations in diabetic cats and compare these with non-diabetic cats of similar age. Samples from 29 cats with DM and 23 non-diabetic cats were analysed. Serum fPLI concentrations were significantly higher in samples from diabetic cats (P < 0.01). A weak association was found between serum fructosamine and fPLI concentrations (R2 ¼ 0.355, P ¼ 0.015), but there was no association between fPLI concentrations and the degree of diabetic control. There were no significant differences in reported clinical signs between cats with or without DM regardless of serum fPLI concentration. This is the first study to demonstrate elevated serum fPLI concentrations in cats with DM, suggesting that pancreatitis could be a significant comorbidity in these cats. Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.
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iabetes mellitus (DM) is one of the most common endocrinopathies in cats. The prevalence of DM in cats has been reported in several studies from different countries and differs substantially amongst studies; geographical variation could, in part, account for these differences (Panciera et al 1990, Baral et al 2003, Rand et al 2004, Prahl et al 2007). The incidence of this disease appears to be increasing, most likely due to changes in the life-style of the feline population (Prahl et al 2003, McCann et al 2007, Slingerland et al 2007). The most common form of DM in cats resembles human type 2 DM, and was initially also called non-insulin dependent DM (NIDDM). In contrast to type 1 DM, where there is an absence of insulin production, type 2 DM is characterised by insufficient insulin secretion in conjunction with impaired insulin action or insulin resistance (Rand 1999). The increased demand on the b cells *Corresponding author. E-mail: [email protected]
1098-612X/08/050480+08 $34.00/0
to produce more insulin in the presence of insulin resistance is suggested to lead to b cell damage and ultimately cell death. Other causes that can induce death of pancreatic b cells include amyloid deposition, glucose toxicity, pancreatitis or dietary factors (Rand 1999). Pancreatitis seems to be an emerging disease in cats, largely due to the fact that its prevalence was previously under-estimated. In contrast to dogs and humans where the disease is rather well-defined clinically, feline pancreatitis is less well understood. Clinical signs and serum biochemical changes are often non-specific and, therefore, the diagnosis is challenging (Zoran 2006). Traditionally, diagnostic investigations included measurement of pancreatic enzymes, diagnostic imaging and pancreatic biopsy. However, more recently, non-invasive diagnosis of feline pancreatitis has been facilitated by the development of a species-specific assay for the measurement of feline pancreatic lipase immunoreactivity (fPLI) concentration in serum.
Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.
Determination of serum fPLI concentrations in cats with DM
Pancreatitis (and particularly chronic pancreatitis) has been cited as a possible cause of poor diabetic control in feline patients with DM (Goossens et al 1998, Feldman and Nelson 2004, Nelson 2005). However, there have been no previous reports assessing the prevalence of pancreatitis in a population of live diabetic cats. The aims of this study were to determine whether serum fPLI concentration was higher in cats with DM, whether serum fPLI concentrations are linked to diabetic control, and whether these cats have any specific clinical signs of pancreatitis.
Materials and methods Study subjects and samples
Serum samples from cats submitted to Nationwide Laboratories (Poulton le Fylde, UK) between November 2006 and February 2007 were used in the study. Samples came from two populations of cats. The first comprised samples from diabetic cats, where serum had been submitted for fructosamine determination. Inclusion criteria were adequate residual volume for fPLI assay, and presence of DM for at least 1 month prior to sampling. A nondiabetic population was generated from surplus serum samples submitted to the same laboratory within a similar time-frame. An attempt was made to include samples with similar signalment to the diabetic cats. Cats with evidence of either hyperthyroidism or hypoalbuminaemia were excluded from the study, because of possible effects on serum fructosamine concentration. Samples that were visibly lipaemic or haemolysed were not included in the study, due to the potential effects of these on the fructosamine and fPLI results. For the fPLI assay, all samples were batched and transported to the Gastrointestinal (GI) Laboratory, Texas A&M University, in a frozen state and on dry ice. fPLI
Serum fPLI was measured by an in-house radioimmunoassay, at the GI Laboratory, Texas A&M University, using the method previously described (Steiner et al 2004). All samples were submitted frozen, coded before analysis, and then analysed in a blinded fashion in a single batch in order to avoid artefactual changes due to inter-assay variability. The previously established reference range for serum fPLI concentration was 2.0e6.8 mg/l, with concentrations
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>12 mg/l being considered indicative of pancreatic inflammation (Steiner 2006). Other assays
Serum fructosamine concentrations were measured by Nationwide Laboratories (Poulton le Fylde, UK) using a colorimetric assay (Cobas Fructosamine assay, Roche, Germany) previously validated for use in cats (Reusch et al 1993, Thoresen and Bredal 1995, Crenshaw et al 1996, Graham et al 1999). The laboratory’s reference interval for serum fructosamine was 146e 271 mmol/l. This was internally established and verified by analysing samples from a population of healthy non-diabetic cats. For the purpose of the study, fructosamine was also determined in the serum of 23 non-diabetic cats to support the validity of this reference range. In the diabetic patients, concentrations of fructosamine <500 mmol/l were considered to represent good diabetic control, whilst those with fructosamine concentrations >500 mmol/l were considered to be evidence for poor control (Feldman and Nelson 2004). When adequate residual plasma volume was available, serum albumin concentrations and either total T4 or free T4 (by equilibrium dialysis) were also assayed by Nationwide Laboratories. Total T4 was measured in 21 of 29 diabetic cats and 20 of 23 non-diabetic cats; free T4 was measured in one of 29 diabetic cats. Confirmed hyperthyroid cats were not included in the study. Serum albumin concentrations were measured in all samples. Questionnaires
Questionnaires were sent to the referring veterinary surgeons of all of cats in the study, in order to acquire information about their clinical signs. The questions were the same for both populations, with the exception of questions about the insulin regime in the diabetic population (Table 1). Given the fact that the non-diabetic population had a higher number of female cats and in order to avoid misinterpretation of results with regards to body mass, the attending veterinary surgeons were asked to provide body condition score (BCS) (Laflamme 1997) instead of body weight. If questionnaires were not returned within 8 weeks, the referring veterinary surgeons were contacted by phone and then again by post. To maximise the return rate, each veterinary surgeon who did not reply initially was contacted a total of three times.
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Table 1. Summary of the results obtained in a questionnaire submitted to the veterinary surgeons responsible for the care of 29 diabetic and 23 non-diabetic cats Diabetic population
Non-diabetic population
fPLI levels (mg/l)
12
12e20
20e50
50
12
12e20
20e50
Fructosamine > 500 mmol/l Fructosamine < 500 mmol/l Overweight (BCS > 5/9) Normal weight (BCS: 5/9) Underweight (BCS < 5/9) Weight loss
1/2 1/2 1/2 1/2 0/2 0/2
3/6 3/6 4/6 1/6 1/6 2/6
5/9 4/9 5/9 2/9 2/9 5/9
3/5 2/5 0/5 3/5 2/5 3/5
0/5 5/5 1/5 1/5 3/5 3/5
0/3 3/3 0/3 0/3 3/3 2/3
0/6 6/6 2/6 0/6 4/6 4/6
Subtotal
2
6
9
5
5
3
6
Total
22
Statistical analysis
Statistical analyses were performed with a computer software package (Minitab v14.0; Minitab Inc), and non-parametric tests were used throughout. ManneWhitney tests were used to compare differences of median serum fPLI concentrations between the cats with and without DM. The diabetic group was further subdivided into two groups; cats with good control and those with poor control of DM, as determined by measurement of serum fructosamine concentration (fructosamine concentrations <500 mmol/l were used as evidence for good control and fructosamine concentrations >500 mmol/l were used as evidence for poor control) (Feldman and Nelson 2004). Once again, ManneWhitney tests were used to compare these groups. Associations between continuous data were assessed by Spearman’s correlation, whilst c2 analysis or Fisher’s exact test (as appropriate) was used to assess differences in presence of weight loss between groups (based on questionnaire data). Differences were considered significant when P < 0.05.
Results A total of 52 serum samples were included in the study, 29 from diabetic cats and 23 from nondiabetic cats. Diabetic population
Of the 29 samples from diabetic cats, 25 were from domestic shorthair (DSH) cats , whilst the remaining samples were from domestic longhair (DLH; n ¼ 2) cats, or from cats of unknown breeds (n ¼ 2). The median age of the diabetic
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population was 12 years (range: 4e18 years). Twenty of the samples were from male cats (16 of which were neutered), seven were from female cats (six neutered) and two were of unknown gender. Non-diabetic population
Of the 23 samples, 17 were from DSH cats, whilst the remainder was from Persian cats (n ¼ 2), DLH cats (n ¼ 2), Birman (n ¼ 1) and one from a cat of an unknown breed. The median age was 13.5 years (range: 8e21 years). Eleven of the samples were from male cats (10 of which were neutered), 11 of the samples were from female cats (10 of which were neutered), and one was from a cat of unknown gender. The median age of the cats in this group was significantly higher than that of diabetic cats (ManneWhitney test, P ¼ 0.008). Fructosamine
Median serum fructosamine concentration was significantly higher in the diabetic population than in non-diabetic cats (ManneWhitney test, P ¼ 0.001; Fig 1). The median fructosamine concentration for diabetic cats was 514 mmol/l (range: 241e782 mmol/l). Sixteen of the diabetic cats had serum fructosamine concentrations indicative of poor control (fructosamine > 500 m mol/l); 12 cats had fructosamine concentrations suggestive of good control (fructosamine < 500 m mol/l) and one had fructosamine concentrations suggestive of periods of hypoglycaemia (241 mmol/l). In the non-diabetic group, the median fructosamine concentration was 238 mmol/l (range: 188e290 mmol/l). One of these cats had a fructosamine concentration of 290 mmol/l,
Determination of serum fPLI concentrations in cats with DM
Fig 1. Box and whiskers plot diagram showing serum fructosamine concentration in the 23 non-diabetic cats and the 29 diabetic cats. The box represents 50% of the population, with the horizontal bar within the box being the median. The whiskers represent the range of fructosamine concentrations for each population and the dots in the figure are outlying values. The median fructosamine concentration was significantly higher in diabetics than in control cats (P ¼ 0.001).
which was marginally above the reference interval from the laboratory (146e271 mmol/l); however, none had fructosamine concentrations that were elevated to a level suggestive of DM or insulin resistance. Fructosamine concentrations were negatively correlated with age (Spearman’s correlation [Rs ¼ 0.404, P ¼ 0.001]). fPLI
The median serum fPLI concentration was higher in diabetic patients (median: 22.5 mg/l, range: 8.1e283.5 mg/l) than in the non-diabetic population (median: 13.8 mg/l, range: 4.6e33.4 mg/l; ManneWhitney test, P < 0.01; Fig 2). No association was found between age and fPLI (Spearman’s correlation [Rs ¼ 0.110, P ¼ 0.468]). No difference in fPLI was found between the four different genders (male, male neutered, female and female neutered) ((KruskaleWallis test,
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Fig 2. Box and whiskers plot diagram showing serum fPLI concentration in the 23 non-diabetic cats and the 29 diabetic cats. The box represents the 50% of the population with the horizontal bar within the box being the median. The whiskers represent the range of fPLI concentration and the dots are outlining values. The median serum fPLI concentration was higher in diabetic patients (median: 22.5 mg/l, range: 8.1e283.5 mg/l) than in the control population (median: 13.8 mg/l, range: 4.6e33.4 mg/l; ManneWhitney test, P < 0.01).
P ¼ 0.786), or when comparing male vs female (regardless of neutering status) Manne Whitney test, P ¼ 0.235). A weak association was noted between serum fructosamine and fPLI concentrations (R2 ¼ 0.355, P ¼ 0.015; Fig 3). However, there was no significant difference in the median serum fPLI concentration between cats considered to have good diabetic control compared to those that had poor diabetic control, as defined by a fructosamine concentration <500 mmol/l or >500 mmol/l, respectively. Based on fPLI concentrations, 24 of 29 (83%) diabetic cats and 15 of 23 (66%) non-diabetic cats had fPLI concentrations which would be suggestive of the presence of pancreatic inflammation (Steiner 2006). Within the diabetic group, five cats had markedly increased fPLI concentrations (>50 mg/l), 11 cats had moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), eight
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Fig 3. Correlation between serum fructosamine and fPLI concentrations in 29 diabetic cats. A weak association was noted between serum fructosamine and fPLI concentrations (Rs ¼ 0.355, P ¼ 0.015). However, there was no significant difference of the median serum fPLI concentration between cats considered to have good diabetic control vs those that had poor diabetic control.
cats had mildly elevated concentrations (fPLI: 12e20 mg/l), and five cats had fPLI concentrations not indicative of pancreatic inflammation (fPLI < 12 mg/l). Within the non-diabetic group, no cats had markedly elevated fPLI concentrations, eight cats had moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), seven cats had mildly elevated concentrations (fPLI: 12e20 mg/l) and eight cats had fPLI concentrations not indicative of pancreatic inflammation (fPLI < 12 mg/l). Questionnaires (Table 1)
A total of 22 questionnaires were received from veterinarians of the group of 29 diabetic cats. None of these cats had vomiting, diarrhoea or abdominal pain. Questionnaires were received from all five diabetic cats with markedly elevated fPLI concentrations (>50 mg/l); four of these five were considered by the attending clinician to have poor control of their DM. Three of these cats had fructosamine concentrations suggestive of poor control of the diabetes (fructosamine concentration > 500 mmol/l); the remaining two cats had fructosamine concentrations suggestive of good control. Three of these five cats had evidence of weight loss.
Nine questionnaires were returned from the group of 11 diabetic cats with moderately elevated fPLI concentrations (fPLI: 20e50 mg/l), five of these cats were considered to have good diabetic control by the attending clinician, whereas four of them were considered to have poor control. Five of these nine cats had weight loss. Six of these cats had fructosamine concentrations suggestive of poor control of their DM (fructosamine > 500 mmol/l). One had fructosamine levels suggestive of periods of hypoglycaemia (fructosamine < 300 mmol/l). The two remaining cats had fructosamine levels suggestive of good diabetic control. Five of these nine cats were overweight. Seven questionnaires were received from the veterinary surgeons of the nine diabetic cats with mildly elevated fPLI concentrations (fPLI: 12e20 mg/l). Four of these cats had fructosamine concentrations that suggested poor diabetic control (500 mmol/l). The three remaining cats had fructosamine levels indicative of good control and the veterinary surgeons of two of these three cats considered the control to be good. Five of these seven cats were overweight. Only one questionnaire was received regarding the five cats with normal fPLI concentrations. On this cat, the diabetic control was good according to the clinical assessment but poor according to fructosamine concentration. Fourteen questionnaires were received regarding the non-diabetic cats. Six questionnaires were received from the veterinary surgeons of the eight non-diabetic cats with moderately elevated fPLI concentrations (fPLI: 20e50 mg/l). Four cats were reported to be losing weight, and their BCS indicated that they were underweight. However, two of these cats were also reported to have concurrent chronic kidney disease. Three questionnaires were received regarding the seven non-diabetic cats with mildly elevated fPLI concentrations (fPLI: 12e20 mg/l). Two cats were reported to have weight loss and were underweight according to BCS. Five questionnaires were returned from veterinary surgeons regarding the eight non-diabetic cats with normal fPLI concentrations. One cat was underweight (BCS: 2/9), had diarrhoea and was on treatment with a depot-steroid preparation for suspected inflammatory bowel disease. A second cat was also underweight (BCS: 3/9) and was reported to have renal and hepatic disease, as well as mammary gland carcinoma. One further cat also had weight loss but
Determination of serum fPLI concentrations in cats with DM
no underlying disorder had been identified by the referring veterinary surgeon. Median BCS was significantly higher in cats with DM than in the non-diabetic cats (Manne Whitney test, P ¼ 0.003). This effect was due both to there being more overweight cats in the diabetic group and more underweight cats in the non-diabetic population (c2 analysis, P < 0.001). There were no other significant differences in the clinical signs between diabetic and non-diabetic cats. Furthermore, no significant differences were noted, for any of the assessed parameters, between cats with abnormal PLI results and those where PLI was normal.
Discussion The study has examined fPLI concentrations in diabetic and non-diabetic cats. Median serum fPLI concentration was significantly higher in the diabetic population, which suggest that pancreatic inflammation may be more prevalent in diabetic cats than in non-diabetic cats. Pancreatitis has previously been mentioned as a cause for DM and poor diabetic control in cats (Goossens et al 1998, Rand et al 2004, Feldman and Nelson 2004, Nelson 2005). It is of note that the three highest fPLI concentrations came from diabetic cats, and the degree of elevation in these cases would be suggestive of severe pancreatitis (Forman et al 2004). A major study limitation was the fact that the finding of increased fPLI implies, but does not confirm, the presence of pancreatic inflammation. Although this is the most likely explanation, there may be other explanations. In this respect, it may be that the diabetic state affects the metabolism of fPLI, or that inter-current pancreatic or nonpancreatic conditions (such as hepatic or renal disease) could affect the metabolism and clearance of fPLI and, therefore, the results of the study. Further, it is possible that other types of pancreatic pathology (eg, pancreatic neoplasia, necrosis or trauma) might also cause increases in fPLI concentration. Therefore, further work would be required to determine the exact reason for elevated fPLI concentrations in the diabetic cats in this study. A second study limitation was the fact that it made use of retrospective data acquired from cats where a sample had been submitted to a commercial laboratory. Thus, the clinical management amongst cats was likely to be variable and clinical information was lacking for some of the study subjects. It also meant
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that neither pancreatic histopathology nor abdominal ultrasonography were available to support the diagnosis of pancreatitis in these cats. The availability of these tests for the study subjects could have helped to provide further support in connecting fPLI elevations with pancreatitis in these cats. Nonetheless, fPLI is reported to be a moderately sensitive (67% in cats with pancreatic pathology) and highly specific (91% in cats without pancreatic pathology) test for pancreatitis (Forman et al 2004); therefore, although it is not possible to conclude that the diabetic cats on this study with high fPLI concentrations were suffering from pancreatitis, this is still the most likely reason. A further limitation of the current study was the fact that the non-diabetic population was significantly older than the diabetic population, and included a greater number of female cats. However, given that there was no significant effect of age on fPLI concentrations, this problem has unlikely affected the findings and conclusions of the study. Further, there was no significant effect of gender on fPLI concentrations, suggesting that differences in the number of female and male cats would not have accounted for the results obtained. The fact that fructosamine concentrations were negatively correlated with age was most likely due to the fact that the non-diabetic population was significantly older than the diabetic group. Moreover, although body weight was likely to have been different between the two groups (because male cats are usually heavier than female cats), this would not have accounted for the differences in body condition, a recognised 9-point system was used for this purpose (Laflamme 1997). A final concern was the fact that hyperthyroidism could not be excluded in a minority of the patients. This could have affected fructosamine or fPLI values. However, there is currently no evidence to suggest that hyperthyroidism affects fPLI values, contrary to what happens with fructosamine (Graham et al 1999). As samples of both groups were handled under the same conditions and analysed as a single batch, dehydration during storage in a frozen state is unlikely to have accounted for differences in fPLI concentrations between these groups. Despite the limitations of the study, the association between elevated fPLI concentrations and the presence of DM is of interest. To explore a possible link with pancreatitis, a questionnaire survey was performed. The responses suggested that all five cats with severely elevated fPLI
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concentrations (>50 mg/l) had been diagnosed with DM for less than 1 year; three of them had weight loss and, according to the clinical signs, the referring veterinary surgeons considered that their diabetic control was poor. Although one of the other two cats was not considered to be underweight by the veterinary surgeon, its body weight was 3.4 kg, which may in fact be low for a neutered male DSH cat. Although severe pancreatitis could have been a cause for weight loss in these three cases, the number of cases is too small to allow statistical assessment. In fact, the weight loss could also have been attributed to poor diabetic control or to the presence of a concurrent disease other than pancreatitis. Nonetheless, it is of note that weight loss was not a feature of the cats with poor diabetic control, but without evidence of pancreatitis, as based on serum fPLI concentration. As expected, median serum fructosamine concentration was significantly higher in diabetic cats than in non-diabetic cats. However, there was not always a clear association between the clinical judgement of diabetic control as specified by the referring veterinarian and serum fructosamine concentrations. Serum fructosamine concentrations consistent with good diabetic control may also be seen in patients that have had periods of both hyperand hypoglycaemia over the preceding weeks due to poor control of DM; this scenario could also occur in the presence of another concurrent disease other than DM that causes similar clinical signs but does not affect fructosamine concentration. Amongst the 14 questionnaires received regarding the cats with moderate and severe elevations of fPLI (fPLI > 20 mg/l) there were four cats for which the fructosamine concentrations were suggestive of good control, but the clinical impression of the attending clinician was that the diabetes was poorly controlled. This might indicate that pancreatitis could be a clinically significant complicating factor in a proportion of diabetic cats, even in those cases in which the fructosamine concentration indicates good control of the diabetes. However, other causes for poor correlation of the clinical signs as perceived by the veterinary surgeons and the fructosamine levels cannot be excluded. As cats with DM are generally middle-aged to old, concurrent diseases other than pancreatitis could also be contributing to the overall clinical picture and could be causing elevations of fPLI.
Currently, pancreatic histopathology is considered to be the gold standard for the diagnosis of pancreatitis in cats. For obvious reasons, this was not available in the cases studied; however, it is important to be aware of the limitations of histopathology, mainly due to the patchy distribution of pancreatic inflammation. A previous study, in which pancreatic histopathology was performed on post-mortem examination of non-diabetic cats, revealed the presence of pancreatitis in 67% of the population examined; this population consisted of cats of both sexes and different breeds with age ranging from 3 months to 21 years and which had died or been euthanased for numerous different problems, including trauma, neoplasia, gastrointestinal tract problems and cardiovascular problems. Forty-five percent of these cats were reported to be clinically normal before they died (De Cock et al 2007). The prevalence of pancreatitis in the study by De Cock et al (2007) was similar to the prevalence of fPLI elevation found in our non-diabetic population. However, the prevalence of fPLI elevation found in diabetic cats in this study was 82%, which is markedly higher than in the population of cats described by De Cock et al (2007). The prevalence of pancreatitis in diabetic cats has, to the knowledge of the authors, only been reported in one previous study in which pancreatic histopathology was performed postmortem in several diabetic Burmese and nonBurmese cats (Lederer et al 2004). In that study, histological evidence of pancreatitis was found in 47% of diabetic non-Burmese cats and in 11% of diabetic Burmese cats. The use of canine PLI (cPLI) was also reported in 40 newly diagnosed diabetic dogs and, on the basis of these results, the prevalence of pancreatitis in diabetic dogs was considered to be 16% (Davidson et al 2003). Furthermore, other studies report that chronic pancreatitis is the cause for DM in dogs in up to 28% of cases (Rand et al 2004). In summary, the findings of this study suggest that fPLI concentrations are higher in diabetic cats when compared to a population of nondiabetic cats. These elevations could represent pancreatitis, although other reasons for the increased fPLI concentrations are possible. Further studies are warranted to assess the influence of pancreatitis in control, progression and management of DM and to clarify the influence of diabetes and other diseases on the metabolism and clearance of fPLI.
Determination of serum fPLI concentrations in cats with DM
Acknowledgements YF is currently undertaking a residency sponsored by the Feline Advisory Bureau. Alexander James German’s senior lectureship is funded by Royal Canin. We would also like to thank the staff at Nationwide Laboratories for their help with the samples and the referring veterinary surgeons who completed the questionnaires.
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