Our RIA (Radio-Immuno Assay) testing options offer practitioners fast and effective results.

This service is specialised and Axiom is one of the only labs in the UK to offer these services and takes many referrals from other laboratory services.

We offer testing options in the following areas within our
in-house RIA Department:



Canine TLI (Trypsin-Like Immunoreactivity)

Trypsin-like immunoreactivity (TLI): This is a species-specific immunoassay that detects circulating trypsinogen, free-trypsin and protein-bound trypsin (hence ‘trypsin-like immunoreactivity’). The pancreas secretes trypsinogen into the intestine, where it is converted to trypsin – a potent digestive protease. In healthy (starved) animals, low levels of TLI are normal.

The principal use of TLI is in the diagnosis of exocrine pancreatic insufficiency in dogs, where the diagnostic sensitivity, specificity and accuracy of decreased serum TLI are almost 100%. There is conflicting evidence about the accuracy of using low TLI to diagnose EPI in cats.

TLI can also be used to diagnose pancreatitis, where increased serum TLI reflects release of trypsinogen or trypsin from damaged acinar cells. However, although elevated TLI is more specific for pancreatitis than increased amylase or lipase, it is not very sensitive, and so has been mostly superseded by the pancreatic lipase immunoreactivity (PLI) assay. Other than pancreatitis, increased TLI can be seen with recent feeding, decreased glomerular filtration rate (due to decreased excretion) and cobalamine deficiency in cats (mechanism unknown).

Insulin

Insulin is a polypeptide hormone originating in the beta cells of the pancreas and serving as a principal regulator for the storage and production of carbohydrates.  The beta cells of the pancreatic islets are responsible for monitoring and controlling the blood glucose concentration.  Unlike most other cells, entrance of glucose into beta cells is independent of insulin.

In the dog or cat with an insulin-secreting tumour, neoplastic beta cells of the pancreas autonomously synthesise and release insulin despite hypoglycaemia.  Failure of insulin secretion to decrease during periods of hypoglycaemia predisposes a dog with a beta cell tumour, to develop clinical signs of hypoglycaemia during fasting and exercise.

Free T4 by equilibrium dialysis

Free T4 by equilibrium dialysis is the gold standard method.  Free T4 (unbound) thyroxine (T4) is the biologically active portion of T4 in the circulation.  The remainder of circulating T4 is protein-bound and biologically inactive.  Protein-bound T4 exists in equilibrium with free T4.

Under normal physiological conditions the concentration of free T4 is held constant by a negative feedback control system involving the hypothalamus, anterior pituitary and thyroid glands.  This regulatory system is unaffected by changes in the concentration of bound T4.  However, patients with disorders of one of these glands may lose normal regulation of free T4 concentrations, and as a result, develop thyroid hormone deficiency (hypothyroidism) or thyroid hormone excess (hyperthyroidism).

17OHP (17 Hydroxy progesterone)

17 hydroxy progesterone can be useful for evaluating the ‘atypical’ Cushing’s case. The main indication is for cases which have classical clinical signs, suspicious supporting changes on haematology and biochemistry; yet negative screening tests i.e. ACTH stimulation tests and Low dose dexamethasone suppression tests.

It is also included in our sex hormone alopecia profile. 17 OHP is a precursor to cortisol in the cortisol production pathway and in occasional cases will be elevated in response to ACTH stimulation when other tests are negative. If the standard ACTH stimulation test has a positive cortisol response there is no added benefit to measuring OHP as well. OHP can be measured on the samples submitted for an ACTH stimulation test and since we routinely keep samples for one week can be requested as an additional test if it seems indicated.

Oestrone sulphate

The oestrone sulphate radioimmunoassay is used to determine pregnancy status in mares, and is also sensitive enough to test for rigs in horses by measuring the oestrone sulphate concentration in serum and EDTA plasma.

For mares - <80 ng/ml – not pregnant or has lost foal.