Glycosylated hemoglobin concentration for assessment of glycemic control in diabetic cats

Establishment of a feline glycated hemoglobin reference interval for a novel dried-blood-spot assay and the effects of anemia on assay results

BACKGROUND

Glycated hemoglobin A1c (HbA1c) reflects long-term (months) glycemic control and has been previously investigated as a monitoring and diagnostic tool in diabetic cats. However, a standardized, reliable, and globally available test and reference intervals (RIs) have not been established. A novel dried-blood-spot card system (A1Care, Baycom Diagnostics) allows for easy collection and evaluation of HbA1c levels in feline patients.

OBJECTIVE

We aimed to establish an RI for HbA1c values in healthy adult cats using the A1Care (Baycom Diagnostics) dried-blood-spot card system.

METHODS

Forty-one healthy client-owned adult cats were enrolled in this study. The RI for HbA1c was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology.

RESULTS

The A1Care HbA1c RI for cats was determined to be 1.9%-3.1%. In healthy cats, A1Care HbA1c values were positively correlated with age (Spearman rho = 0.4 [95% CI 0.1 to 0.6], P = 0.01). In 50% of anemic cats, the A1Care HbA1c value was above 3.1%. There was a weak negative correlation between the A1Care HbA1c value and PCV (Spearman rho = -0.4 [95% CI -0.6 to -0.1]).

CONCLUSIONS

This study established an RI for HbA1c in healthy adult cats similar to previously reported RIs. Future clinical studies are necessary to substantiate that this RI can differentiate diabetic from nondiabetic cats. Further long-term clinical studies will be valuable to determine if HbA1c values can be used as a screening test for prediabetes in cats.

Update on Drugs Used to Treat Endocrine Diseases in Small Animals

Drug therapy for the endocrine system is implemented to replace a hormone deficiency or to prevent or reduce the formation or effects of excess hormone. Treatment of endocrine disorders covers diseases of the pituitary, adrenal, parathyroid, and thyroid glands as well as the endocrine pancreas. This article focuses on new therapies currently available for specific diseases. Administration of trilostane for treatment of hyperadrenocorticism and use of insulin glargine, protamine zinc insulin (PZI), and porcine Lente insulin for diabetes mellitus are discussed. In addition, transdermal methimazole therapy for treatment of feline hyperthyroidism and administration of progestins for pituitary dwarfism are considered.

Evaluation of a continuous glucose monitoring system for use in veterinary medicine

BACKGROUND

With the emergence of continuous glucose monitoring systems being used to provide a detailed glucose picture in humans, a commercially available system (CGMS(R), Medtronic Minimed, Northridge, CA) was examined for use in veterinary species.

METHODS

Adult, clinically normal horses (n = 7), cats (n = 3), dogs (n = 4), and cows (n = 5) were studied. Cats (n = 4), dogs (n = 5), and one horse with diabetes were included in the study. Several of the normal horses, including the horse with diabetes, and one cow were subjected to an intravenous glucose tolerance test. The CGMS was attached to each animal, and the recorded interstitial glucose concentrations were compared with whole blood glucose concentrations as determined by a point-of-care glucose meter. Events such as insulin administration, feeding, travel, or administration of intravenous glucose were all noted and compared with results from the CGMS.

RESULTS

There was a positive correlation between interstitial and whole blood glucose concentrations for all the clinically normal species, those with diabetes mellitus, and those receiving intravenous glucose. Events such as feeding, glucose or insulin administration, and transport to the clinic were noted by the owner or clinician and could be identified on the graph and correlated with time of occurrence.

CONCLUSIONS

Our data indicate that the use of the CGMS is valid for use in the species examined. Use of this system alleviated the need for multiple blood samples and the stress associated with obtaining those samples. This system may provide greater monitoring capabilities in patients with diabetes and promote the diagnostic and research potential of serial glucose monitoring in veterinary species.

Diabetes mellitus in cats

Feline diabetes is a multifactorial disease with genetic and environmental factors, including diet, excess body weight, and physical inactivity, involved in its pathogenesis. Although type 2 diabetes is most common in cats, most cats are insulin-dependent at the time of diagnosis. If good glycemic control can be achieved early after diagnosis, a substantial proportion of diabetic cats go into clinical remission. Diabetic remission may be facilitated by using a low-carbohydrate-high-protein diet combined with a long-acting insulin, such as glargine, administered twice daily. Rather than just controlling clinical signs, these new treatment modalities make curing feline diabetes a realistic goal for practitioners.

Evaluation of a continuous glucose monitoring system for use in dogs, cats, and horses

OBJECTIVE

To evaluate a continuous glucose monitoring system (CGMS) for use in dogs, cats, and horses.

DESIGN

Prospective clinical study. Animals-7 horses, 3 cats, and 4 dogs that were clinically normal and 1 horse, 2 cats, and 3 dogs with diabetes mellitus.

PROCEDURE

Interstitial glucose concentrations were monitored and recorded every 5 minutes by use of a CGMS. Interstitial glucose concentrations were compared with whole blood glucose concentrations as determined by a point-of-care glucose meter. Interstitial glucose concentrations were also monitored in 2 clinically normal horses after oral and i.v. administration of glucose.

RESULTS

There was a positive correlation between interstitial and whole blood glucose concentrations for clinically normal dogs, cats, and horses and those with diabetes mellitus. Events such as feeding, glucose or insulin administration, restraint, and transport to the clinic were recorded by the owner or clinician and could be identified on the graph and associated with time of occurrence.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data indicate that use of CGMS is valid for dogs, cats, and horses. This system alleviated the need for multiple blood samples and the stress associated with obtaining those samples. Because hospitalization was not required, information obtained from the CGMS provided a more accurate assessment of the animal's glucose concentrations for an extended period, compared with measurement of blood glucose concentrations. Use of the CGMS will promote the diagnostic and research potential of serial glucose monitoring.

Management of feline diabetes mellitus

Up to one quarter of diabetic cats can be well controlled with oral hypoglycemic drugs, although at least 75% require insulin therapy. Most available insulins provide good clinical control but only moderate glycemic control. Because mild to moderate hyperglycemia is well tolerated by cats receiving insulin but hypoglycemia can be life threatening, conservative insulin dosing is recommended. Clinical signs and water intake indicate whether a dose adjustment is required, but serial blood glucose measurements are usually needed to determine the direction of the adjustment. Starting doses of 0.3 to 0.5 IU/kg administered twice daily (rounded down to the nearest whole unit) are usually safe. Dose adjustments should not exceed 1 IU per cat every 2 to 4 weeks unless clinical hypoglycemia has occurred. Cats with clinical hypoglycemia need to be reassessed to see if they are in remission. If not, a 50% to 75% reduction in dose is advised. Approximately 30% of cats go into diabetic remission 1 to 4 months after an adequate treatment protocol is instituted.

Effect of dietary insoluble fiber on control of glycemia in cats with naturally acquired diabetes mellitus

OBJECTIVE

To evaluate effects of dietary insoluble fiber on control of glycemia in cats with naturally acquired diabetes mellitus.

DESIGN

Randomized controlled crossover trial.

ANIMALS

16 cats with naturally acquired diabetes mellitus.

PROCEDURE

Cats were fed a diet high in insoluble fiber (HF) containing 12% cellulose (dry-matter basis) or a diet low in insoluble fiber (LF) for 24 weeks; they were fed the other diet for the subsequent 24 weeks. Caloric intake and insulin treatment were adjusted to maintain stable body weight and control of glycemia, respectively. Cats were allowed an adaptation period of 6 weeks after initiation of a diet, after which control of glycemia was evaluated at 6-week intervals for 18 weeks. Variables assessed included serum glucose concentration measured during the preprandial state, blood glycated hemoglobin concentration, serum glucose concentration measured at 2-hour intervals for 12 hours beginning at the time of the morning insulin injection, 12-hour mean serum glucose concentration, and mean fluctuation in serum glucose concentration from the 12-hour mean serum glucose concentration.

RESULTS

Mean daily caloric intake, body weight, or daily insulin dosage did not differ significantly between cats when fed HF and LF diets. Mean preprandial serum glucose concentration, most post-prandial serum glucose concentrations, and the 12-hour mean serum glucose concentration were significantly lower when cats consumed the HF diet, compared with values when cats consumed the LF diet.

CONCLUSIONS AND CLINICAL RELEVANCE

These results support feeding a commercially available diet containing approximately 12% insoluble fiber (dry-matter basis) to cats with naturally acquired diabetes mellitus.

Current understanding of feline diabetes: part 2, treatment

When treating diabetic cats, the primary aim is to control clinical signs without causing clinical hypoglycaemia. Secondary goals are to maximise the chances of attaining diabetic remission and to minimise the risk of complications due to chronic hyperglycaemia. A treatment plan that is convenient for the owner is important for compliance. Underweight or overweight diabetic cats should be fed with the aim of normalising bodyweight. Current evidence suggests that non-obese diabetic cats can be fed ad libitum. The oral hypoglycaemic drug glipizide is well established as a treatment for about a third of diabetic cats, which have residual beta cell function. Preliminary studies on other oral agents such as vanadium salts, metformin, and troglitazone indicate a potential use in some diabetic cats. Insulin treatment remains the treatment of choice for the majority of diabetic cats. Choice of insulin, dose rates and monitoring of treatment are discussed.

Diagnostic utility of glycosylated hemoglobin concentrations in the cat

Changes in glycosylated hemoglobin (GHb) concentrations, K values (% disappearance of glucose/min after an intravenous injection of 1 g/kg dextrose), and blood glucose concentrations were examined in eight cats before and during the induction of diabetes, and in four of these cats after they were placed on insulin treatment. There was a statistically significant separation of GHb, K values, and fasting blood glucose concentrations between healthy and diabetic cats. Changes in GHb correlated best with the K value and single weekly fasting glucose concentrations averaged over eight periods for each cat while diabetes was induced (R = 0.80 and 0.78, respectively); however, fasting blood glucose concentrations obtained on the day of the GHb measurement were also highly correlated (R = 0.69; P < 0.001). The correlation between GHb and single weekly glucose concentrations obtained in insulin-treated cats at the time of insulin peak action and averaged over an 8-wk time period for each cat was less but still significant (R = 0.53; P < 0.001). It is concluded that GHb measurements are a simple and reliable way to monitor changes in glucose control in the diabetic cat over a prolonged period.

Glycated haemoglobin in various pathological conditions: investigations based on a new, fully automated method

A new automated affinity chromatographic method for determining glycated haemoglobin (GHb) in dogs and cats was tested. The method appeared to be practical, quick and accurate. The reference range, calculated on the basis of 50 healthy dogs and 43 healthy cats, lay between 2.4 and 3.4 per cent in dogs and 2.0 and 2.9 per cent in cats. Concentrations were not influenced by age or gender. GHb levels obtained for 21 dogs and 18 cats with newly diagnosed diabetes mellitus were significantly higher than those of the control animals, ranging from 4.5 to 8.6 per cent (median 6.1) in dogs and from 2.7 to 6.0 per cent (median 3.8 per cent) in cats. The GHb levels in 31 normoglycaemic dogs with anaemia ranged from 2.3 to 4.3 per cent (median 3.3 per cent), and those of 22 normoglycaemic cats with anaemia from 2.6 to 3.9 per cent (median 3.2 per cent); both sets of levels were significantly elevated compared to control group values. GHb concentrations in animals with polycythaemia, azotaemia or liver disease showed no significant deviations from the control group; in individual cases they were slightly elevated compared to the reference range. The automated measuring method employed can be used to determine GHb in dogs and cats. Anaemic animals should generally be excluded from the GHb determination.