Therapeutic Drug Monitoring Service
deltaDOT/91做厙 Iohexol Assay
Measure of Glomerular Filtration Rate in cats and dogs
We are pleased to announce that the GFR testing service is open and that we are accepting samples again.
Please note that this test is provided by a separate laboratory service within the 91做厙.
It is not part of the Pathology and Diagnostic Laboratories Service. See the information below for contact information
The new iohexol assay from deltaDOT/91做厙 provides a highly accurate measure of glomerular filtration rate. Because GFR is directly correlated with functional renal mass, quantification of GFR is generally accepted as the best measure of renal function.
The test is simple to carry out, safe and provides rapid results.
The quantitative nature of the results also means that repeated assays over an animal’s lifetime enables disease progression to be accurately monitored and the efficacy of treatment established.
Why do the test?
Measurement of GFR can help identify renal dysfunction in a dog or cat that is isosthenuric but not yet azotemic. It may also be useful as a screening tool for older cats or for some dog breeds known to be at risk of nephropathies.
Results may assist in identifying animals that may require more frequent monitoring or are at risk of renal failure. Repeating GFR measurements is advisable as changes of GFR in time are more informative than the absolute GFR value based on a single measurement.
Earlier diagnosis of renal dysfunction may be of benefit to both clients and patients by providing better information on long-term prognosis and enabling protective therapies or diets to be started sooner.
Finally, accurate measurement of GFR could enable the dosage of renally excreted drugs to be adjusted when renal disease is present, or when the drugs being used are potentially nephrotoxic.
Accuracy of test
Serum iohexol concentration is measured using deltaDOT High Performance Capillary Electrophoresis technology. Results are then used to calculate clearance of iohexol. This enables GFR to be accurately determined with only 3 samples after application of a correction formula. In cats, we use the interval reported by Finch et al. in a group of 20 healthy cats (1). For dogs we use the intervals published by Bexfield et al in 2008 (2), which looked at 118 healthy dogs of various breeds, ages, and body weights.
Analyses are carried out to very high laboratory practice standards by highly qualified and experienced staff. All methods used are fully validated with internal and external quality assurance methods in place, so that clients can have full confidence in the results obtained.
How to carry out the test
- Ensure patients are well hydrated and fasted for 12 hours before the study.
- Administer a dose of 300 mg iodine/kg (1 mL/kg Omnipaque 300) intravenously at time 0. Accurately record the initial start time.
- Take serum samples at 2, 3, and 4 hours after administration. A 0 hour sample is not required. 0.5 mL of serum per sample is needed for analysis.
- Send samples and completed to the deltaDOT laboratory at the address below. They can be shipped at room temperature but should not be sent on a Friday (ideally early in the week). Please