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What should I do if I have a
question about a sample submission or interpretation of a
result?
If the answer to your question is not in this FAQ section,
please feel free to call IDEXX Laboratories at +44 (0)1937 544000.
Our clinical pathologists can answer your questions on
cytology specimens and interpretation of results. Our
pathologists can answer your questions about biopsies and
necropsies. Two of our pathologists have expertise in exotic
animals, one pathologist has expertise in avian disease, and
our clinical pathologists are knowledgeable in
interpretation of large animal clinicopathologic test
results. In addition, our Client Services and Admin teams
can help you with general information questions, including
sample submission, and our laboratory manager and laboratory
technicians can answer questions about specific equipment
or test procedures.
What should I do if I want to
submit a sample for a test that is not listed on the Test
Request Form?
Please call IDEXX Laboratories at +44 (0)1937 544000. Many
additional or specialised tests are available at the
laboratory.
What should I do if I do not
think I can obtain enough blood for all the tests I
want to request on a specific patient?
Please telephone the laboratory at +44 (0)1937 544000. We may
be able to help you prioritise the testing or provide
alternatives and write your priorities on the request
form.
What is the minimum volume
needed for a full blood count?
If you use a standard 1.3 ml EDTA (pink-top tube), please
fill to the "fill line" to ensure a good quality sample.
Always submit a smear.
What is the minimum volume of
serum needed for a chemistry screen?
At least 0.5 ml of serum is needed.
What is the minimum volume of
serum needed for a cortisol assay?
At least 0.5 ml of serum is needed.
What is the minimum volume of
serum needed for a total T4 and a free T4?
At least 0.6 ml of serum is needed.
What is the minimum volume
needed for a coagulation profile?
For determining the PT/PTT, the ratio of blood to
anticoagulant (citrate) is critical (1 part citrate: 9 parts
blood). For the 1 ml green-top citrate tubes we provide,
each tube requires 1 ml blood. Please fill to the correct
level and ensure the tube is within date.
Will the test results be altered
if the full blood count, serum chemistry, or urine sample
sits at room temperature overnight?
Serum enzymes can be affected when the sample is stored at
room temperature, especially when the serum has not been
separated. Depending on the species and breed, potassium may
be artefactually increased, especially when haemolysis is
present.
Cell morphology is compromised (full blood count) when the
sample sits. If a well-made blood smear slide was made at
the time of the sample collection, the differential and
assessment of the cell morphology and adequacy can still be
accurate.
Urine pH, crystals and cell morphology change with delayed
handling. The most accurate information is always acquired
when the urine is evaluated immediately after collection.
What are platelet clumps and how
can I avoid them?
Platelet clumps are formed during phlebotomy, in storage in
the EDTA tube, or during preparation of the blood smear.
They represent the normal adhesion tendency of platelets and
are "artefacts" in that they are not circulating in the
patient's blood. The clumping becomes important in
interpretation of platelet numbers. When the platelets
are not evenly distributed in the sample, the platelet
count may underestimate the platelet number. At IDEXX
Laboratories, laboratory technicians evaluate a blood
smear from every CBC to estimate platelet numbers and
note the presence of platelet clumps.
Platelet clumping can be minimised by getting a "clean
stick" during phlebotomy, immediately putting the blood into
the EDTA tube, and gently mixing the sample. Sometimes this
is not enough to prevent platelet clumping. When blood from
a patient repeatedly has too many platelet clumps to
accurately assess platelet numbers, a blood sample can be
drawn into a heparin-flushed syringe before putting the
sample into the EDTA (pink-top tube). Platelet clumping is
reduced by use of jugular vein samples wherever possible.
Which test should I use to
diagnose an active toxoplasmosis infection?
A serum IgM and IgG titre is the test of choice to diagnosis
active disease. Often, a convalescent titre is needed. The
available assays for IgM and IgG are in the USA and hence
turnaround is approximately 10 days. For this reason, we
recommend institution of therapy following sample
collection whilst awaiting results.
Will lipaemia affect the
cortisol or thyroid assay?
There is no problem measuring cortisol or thyroid hormone
concentrations in lipaemic samples. We ultracentrifuge
lipaemic samples before performing the assay to obviate that
problem. Otherwise, lipaemia will affect test results.
Does the blood sample for insulin have
to be centrifuged?
YES. Proper handling of the sample is critical. The blood
should be centrifuged as soon as the clot has formed. The
serum must be decanted and kept cold. Haemolysis will alter
the results. If the sample is haemolysed, a fresh sample
should be collected. To help diagnose an insulinoma, the
[insulin] should be measured when the blood glucose
is < 60 mg/dl. Serum or plasma (grey-top tube)
glucose concentration determination is included in the
price for the insulin assay.
For the diagnosis of insulinoma, a simultaneous fluoride
oxalate sample should be submitted with the separated
serum after a 12-14 hour fast, or when In-Clinic analysis
indicated hypoglycaemia is present. Fluoride sample is
used to check blood glucose and allow calculation of an
amended insulin:glucose ratio.
Does the blood sample for
insulin have to be centrifuged?
YES. Proper handling of the sample is critical. The blood
should be centrifuged as soon as the clot has formed. The
serum must be decanted and kept cold. Haemolysis will alter
the results. If the sample is haemolysed, a fresh sample
should be collected. To help diagnose an insulinoma, the
[insulin] should be measured when the blood glucose is <
60 mg/dl. Serum or plasma (grey top tube) glucose
concentration determination is included in the price for
the insulin assay.
For the diagnosis of insulinoma a simultaneous fluoride
oxalate sample should be submitted with the separated
serum after a 12-14 hour fast, or when in house analysis
indicated hypoglycaemia is present. Fluoride sample is
used to check blood glucose and allow calculation of an
amended insulin:glucose ratio.
What test should I use in a dog
or cat that previously has been spayed, but appears to have
behaviour similar to oestrus?
DOGS:
There are 3 options depending on where the dog is in the
oestrous cycle.
- Vaginal cytology: The vaginal epithelium
is a good biologic assay for the presence of
oestrogen. If the dog is in late pro-oestrus
or oestrus, one should see > 60% superficial
cells.
- Basal Serum Progesterone: If the dog had
signs of oestrous 2 weeks to < 2 months ago, a
single serum progesterone concentration may be
diagnostic (evidence of luteal structure).
- HCG stimulation test: Progesterone is
measured 1-3 weeks after administration of HCG
during behavioural oestrus. Protocol for this test
is given in our section on Ovarian remnant
syndrome.
NB: Progesterone assay must be undertaken on serum
samples that have not been collected or stored in gel
separation tubes as this will significantly reduce the
measured concentration.
CATS:
HCG stimulation test is also valid for this species.
Serum samples for progesterone must not be submitted in
gel separation tubes.
What should I use in a dog or
cat if the animal is supposed to be castrated but is
exhibiting male-like behaviour?
Basal testosterone is very often diagnostic and should be
assayed initially on a serum sample. In the rare cases in
which the result is equivocal, HCG stimulation test can be
undertaken in both species.
What lab test can I use to determine if
a bitch is pregnant?
The plasma relaxin concentration rises after implantation of
the canine foetus. If the bitch was bred at the appropriate
time in her oestrous cycle, pregnancy can be detected as
early as 28 days after the last mating.
When should the blood sample be
collected for therapeutic monitoring of
phenobarbitone?
In a recent study reported at the ACVIM forum in June,
researchers from the University of Wisconsin reported that
in most dogs, there are no significant difference serum
phenobarbitone concentrations in samples obtained prior to
dosing, or at 3 or 6 hours postpill. The exception was in a
dog receiving a high dose (10 mg/kg/day) of phenobarbitone.
Importantly, the dogs in the study were receiving the same
dose of phenobarbitone for at least 7 days, and were
not receiving any other drugs that may have an effect on
serum phenobarbitone concentrations (P450 enzyme inhibitors,
such as cimetidine). Thus, when you are monitoring
therapeutic serum phenobarbitone concentrations in dogs, you
can collect a sample at any time of the day as long as: 1)
the dose has been constant for at least 7 days; 2) the dog
is not receiving any drugs that would alter the P450
enzymes; and 3) the dog is receiving < 8 mg/kg/day of
phenobarbitone.
How should I submit a sample for
cytologic evaluation?
In general, fluid submissions should comprise an EDTA
sample to which 2-3 drops of neutral buffered formal-saline
have been added, and air-dried smears.
Air-dried smears are required for cytology of solid lesions.
Bone marrows require air-dried smears made by squash
preparation of marrow spicules and an EDTA sample of
peripheral blood.
For liquid samples, also be sure to send along some of the
fluid in tubes. EDTA (pink-top) is preferred for cytology
and a plain tube is required for culture. Do not use serum
separator tubes for cytologic specimens.
I want to know if there are neoplastic
cells in a urine sample. What test do I request - urinalysis
or cytology?
Neoplastic cells in the urine are best assessed with a
cytology evaluation. Routine urinalysis sediment examination
is quantitative rather than qualitative. For advice on
submission of urine samples for cytology, please see the
cytology section.
We have recently introduced the V-Bladder Tumour Antigen
test that has been reported to be more sensitive in the
detection of transitional cell carcinoma than cytology.
This test is performed on fresh urine and can be combined
with cytological evaluation.
How can I get the most valuable
information from a skin biopsy?
Providing the pathologist with following information should
greatly help in the interpretation of biopsy:
- The distribution and duration of the
lesion(s)
- A list of current and
previous medications
How do I interpret a LDDS in a
dog?
Before embarking on testing, and before one can interpret
the LDDS test, there are 4 important points to keep in
mind:
- Stressful disease (sick, poorly controlled
diabetics, renal failure, etc) may cause false positive
test results. So the patient's stressful disease must be
controlled before considering testing for
hyperadrenocorticism. Also, potentially stressful
procedures should not be performed during the 8 hour
test (anaesthesia, sedation, or procedures that will
need excessive restraint or cause excessive discomfort
to the patient.
- Prednisolone and prednisone, and other
corticosteroids (except dexamethasone), cause
interference with the assay. The animal should not have
received these drugs during the 24 hours prior to sample
collection.
- Topical (skin, ears, eyes) steroids may cause
iatrogenic hyperadrenocorticism. These dogs may have all
the clinical signs and laboratory tests typical of
Cushing's disease and the owners may forget to mention
to you that they are applying a topical cream. So, do
not forget to ask the client if they are using ANY
topical medication before embarking on diagnostic
testing for hyperadrenocorticism.
- No test is 100% specific and 100% sensitive. At
times, additional or repeated testing is needed to
confirm your clinical suspicion of
hyperadrenocorticism.
The primary reason to perform a LDDS is to confirm a
clinical suspicion of hyperadrenocorticism. If the
history, physical examination results and initial
database are not consistent with hyperadrenocorticism,
interpretation of the test result may not be
accurate.
What diagnostic tests can be used to
differentiate adrenal versus pituitary hyperadrenocorticism
(if one cannot make that determination from the LDDS test
result)?
- Plasma (ACTH)
- High dose dexamethasone suppression test
- Adrenal ultrasonographic evaluation
Why does the type of urine crystal
change from one sample to another in the same
dog?
Formation of detectable crystalluria is dependent on the
temperature, the pH, urine concentration, diet, metabolic
abnormalities, drugs and specimen handling. Some of these
factors may be quite variable (ex. the postprandial alkaline
tide may result in altered urine pH compared to a fasting
sample, changing the diet and/or changing the pH in the
sample may alter the type of crystal seen). The best method
of avoiding artifactual alterations in the urine sediment is
to evaluate the urine specimen immediately after collection,
with the sample still at body temperature.
How can one explain a fasting bile acids
(BA) that is higher than the postprandial bile
acids?
There are several possible explanations for this type of
result.
- Food was not withheld for the 8-12 hours
- Only 30-50% of the newly formed BA is stored, so
there is some secretion of newly formed BA
- There is delayed gastric emptying (highly stressed,
or sedated patient)
- Postprandial gall bladder contraction releases a
variable amount of bile (5-65%), so that the
postprandial sample is "lower than expected"
- Bacterial overgrowth augments the unconjugated BA
pool, which enters the systemic circulation more readily
- Mis-identification of samples
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