ANNUAL PREVENTIVE HEALTH SCREENING
W. Jean Dodds, DVM
938 Stanford Street
Santa Monica, CA
310-828-4804; Fax 310-828-8251
Maintaining health and
longevity of today’s companion animals requires not only careful observation of the dogs overall well-being on a regular
basis, but also depends upon annual preventative health examination and screening by your veterinarian. A preventive health program should include annual blood and urine profiles, and regular maintenance dental
and ear cleaning, along with routine grooming and toenail trimming. This type of annual examination is especially important
for senior companion animals over seven years of age. If the preventive health examination and testing reveals some outward
or underlying disease process, more sophisticated testing with ultrasonography, radiology, and cardiology, and/or more specific
diagnostic laboratory testing for the suspected condition can be performed.
Today, with the availability of on-site and referral diagnostic laboratories,
and the ability to transmit radiographs and electrocardiograms by computer-technology, experts in various parts of the country
can provide input to the local veterinary practitioner. This allows your veterinarian to restore optimum health to your dog
as soon as possible.
Screening of Senior Dogs
As laboratory tests play
an important role in the overall evaluation of animal patients, clinical study of routine laboratory parameters has been conducted
to document the findings in healthy senior dogs. As an animal ages, there is a definite loss of functional reserve capacity
of every organ system. These changes of aging may affect laboratory data without necessarily reflecting the presence of a
disease process and should be considered when interpreting laboratory values in senior patients.
Results of the health profiling
in 100 healthy senior dogs indicated that 15 (17%) dogs had an increase in their liver-adrenal function enzyme, alkaline phosphatase
(ALP). Four of them also had increased urine cortisol:creatinine ratios (UCCR),
suggesting the possibility of hyperactive adrenal glands (Cushing’s syndrome), and 3 of the 4 were confirmed to have pituitary-dependent Cushing’s disease by the low-dose dexamethasone suppression
In 26 (29%) dogs, the total T4 thyroid values
were below normal, and 9 of 11 dogs evaluated further with more complete thyroid function tests were diagnosed with hypothyroidism.
This finding underscores the need for complete thyroid profile testing and not just a T4 screening test.
Eleven (11%) dogs had bacteria and pus in
their urine. Four of them had elevated blood [chemistry kidney blood chemistry values, thus highlighting the importance of
performing a urinalysis, as part of the routine health assessment.
Thus, despite the fact that these dogs were not being treated for any underlying medical problems, clinically
significant disease was found in more than 20% of them.
Routine Laboratory Profiles
The descriptions below outline the basic testing required for a comprehensive annual
Blood Count (CBC)
CBC reflects the output of blood cells from the bone marrow and lymph nodes, and of blood cell stored in the spleen and liver.
It includes: the white blood cell count (WBC), red blood cell count (RBC), hemoglobin
(HGB), hematocrit (HCT), red blood cell indices (MCV, MCH, MCHC), and platelet estimate and/or platelet count. The differential count examines the number of specific types of white blood cells, namely, neutrophils,
lymphocytes, monocytes, eosinophils, and basophils.
A series of serum chemistry tests is run to help assess
various body organs and functions. In several instances, the same test analyte reflects the effects of more than one organ
Liver Function Tests
that measure or are influenced by liver function include: aspartate aminotransferase (AST, formerly SGOT), alanine aminotransferase
(ALT, formerly SGPT), total bilirubin (direct and indirect), alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT),
cholesterol, and albumin.
Kidney Function Tests
that measure or are influenced by kidney function include: blood urea nitrogen (BUN), creatinine, calcium, phosphorus, albumin,
Gastro-Intestinal Function Tests that measure or are influenced by gastro-intestinal function include:
total protein, albumin, total bilirubin, amylase, lipase, triglycerides, sodium, potassium, and chloride.
Pancreatic Function Tests that measure or are influenced
by pancreatic function include: amylase, lipase, and glucose.
Adrenal Function Tests that
measure or are influenced by adrenal function include: alkaline phosphatase (ALP), sodium, and potassium, plus other more specific dynamic tests of adrenal activity.
Muscle Function Tests
that measure or are influenced by muscle function include: creatine phosphokinase (CPK) or creatine kinase (CK), calcium and corrected calcium [the true concentration of calcium in dogs has to be corrected (adjusted upwards) whenever the albumin concentration is below 3.5 g/dL], magnesium (not a useful
diagnostic aid in dogs), aspartate aminotransferase (AST, formerly SGOT), and alanine aminotransferase (ALT, formerly SGPT).
Immune System Function
Tests that measure or are influenced by immune function include:
globulins and lymphocytes.
Complete Thyroid Profile
A complete thyroid profile is needed, at least initially, to screen healthy breeding stock for autoimmune
thyroiditis and to diagnose hypothyroidism. Routinely screening with only a T4 test or using an in-office T4 test is not
sufficient to rule in or rule out thyroid dysfunction. A minimum profile of just
T4 and freeT4 may be acceptable, when monitoring adequacy of dose for a dog taking thyroxine supplement --- if he/she did
not have thyroiditis when tested within the previous year, or if the cost of more complete testing is of serious concern.
The complete thyroid profile includes:
T3, T4 , Free T3, Free T4 ,T3 autoantibodies,T4 autoantibodies, and thyroglobulin
autoantibodies. The freeT4 assay can be measured by several valid methods, although the most commonly used are an analog radioimmunoassay
or the two-stage equilibrium dialysis (ED) radioimmunoassay. Canine endogenous
thyroid stimulating hormone (TSH) can also be measured, but it is poorly predictive of primary hypothyroidism in dogs (70%),
and can give 20-40% discordant results [both false positive and false negative]. This finding has been verified by several
published studies. The reason is unclear, but it appears that the dog has some alternate pathway for regulating thyroid stimulation.
and Treating Thyroid Dysfunction
All animals are not the same
higher basal thyroid levels than adults
have lower basal thyroid levels than adults
treatment is best given twice daily
· Dividing the daily dose every 12 hrs avoids undesirable “peak and valley”
· Achieves better steady state over 24 hrs; thyroxine half life is 12-16 hrs
be given directly by mouth rather than in food bowl
Testing animals on thyroxine therapy
should be drawn 4-6 hrs post-pill for twice daily therapy
needed is T4 and freeT4
profile preferred; a must for all thyroiditis cases
for Canine Thyroid Dysfunction
· Complete thyroid antibody profile preferred
· TSH poorly predictive in dogs (~ 70%) as compared to humans
· Basal levels affected by certain drugs (steroids, Phenobarbital, sulfonamides)
· Basal levels lowered by estrogen; raised by progesterone
[sex hormonal cycle effects], so test intact bitches during anestrus
Screening for Canine Autoimmune Thyroiditis
thyroid antibody profile required
bitches during anestrus
T4AA, TgAA; not just freeT4, TSH, TgAA
Registry is limited panel
(~8%) are T3AA and/or T4AA positive, but TGAA negative
Treating Canine Autoimmune Thyroiditis
cases positive for T3AA and/or T4AA, or TgAA
wait until dog gets ill or has aberrant behavior
low-grade TgAA positive , retest profile in 2-4 mos
thyroxine twice daily; retest profile in 2-4 mos
with thyroid antibody profile
Do NOT breed dogs with autoimmune thyroiditis
· Heritable trait, regardless of clinical status
· Screen relatives annually from puberty
Consider for breeding,
if negative, after age three
available upon request ]