American Society for Veterinary Clinical Pathology
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Madison, WI 53704

Telephone: +1-608-443-2479
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2.9. Radioimmunoassay


2.9.1. Government Regulations for RIA.

Government regulations and licensing requirements may vary with city, state, province and country. In general, minimum requirements for safe radioisotope handling are indicated. Requirements include personnel safety training, radioactive isotope monitoring, proper radioisotope disposal, and periodic inspection. Licensing is required for the purchase of radioactive isotopes. A laboratory considering performing RIAs should first determine whether it meets these standards and obtain licensure before establishing the procedures.

2.9.2. Monitoring – see General Recommendations

2.9.3. Method Validation.  Any radioimmunoassay should be validated for the species for which it will be used. Validation should include one of the methods out-lined below.

a. Articles in refereed veterinary journals for the particular test (if available) should be reviewed. It is not good practice to rely on the manufacturer's testing alone. The test should be validated independently.

b. If the test cannot be substantiated through independent validation, then the following minimum evaluation is necessary:

i. Run-to-run precision - minimum of 10 data points. 20 data points may improve the accuracy of the estimate.

ii. Within-run precision - minimum of 10 data points. 20 data points may improve the accuracy of the estimate.

iii. Recovery procedures - use a purified natural substance for each species, where possible. Recovery should be performed using both high end and low concentration samples.

iv. Evaluation of interfering substances such as hemolysis, lipemia, bilirubinemia, medication interactions, etc.

v. Parallelism - dilutions and details of linearity.

vi. Reference intervals should be generated and maintained fro each test. Please refer to the ASVCP Guidelines for Reference Intervals and Decision Thresholds

vii. Standard curves are needed for each test. Some gamma counters can store curves. If this is implemented in routine testing, validation of the procedure should be present.

2.9.4. Instrumentation – see General Recommendations

2.9.5. Personnel Knowledge – see General Recommendations

2.9.6 Quality Control

a. A minimum of 3 control materials should be assayed with each test. These can include commercial controls for high, normal and low values or samples developed in-house.

b. Interpretation of RIA results often depends on methodology and on reference values established in-house, making it difficult to use some types of external control systems. It is recommended that when using external control materials that in-house materials also be analyzed and interpretation compared.

c. External controls should be used and plotted at least quarterly.

d. All control material results should be recorded and plots and values should be readily accessible to personnel running the tests. Levy-Jennings plots are acceptable.

e. An action plan must be in place that details acceptance or rejection of patient test results based on control values.

f. If the procedure, as detailed by the manufacturer or published articles is modified (ie, only 1 tube per patient), documentation should be available to show that test precision and accuracy are still acceptable with the modification(s).

2.9.7. Procedures Manual – see General recommendations

2.9.8. Comparison of test results – see General Recommendations

2.9.9. Identification of out-sourced tests – see General recommendations