It has been a great pleasure for every one of us in Thyrocare to teach Radio immunoassays and we have been enjoying it for the last
30 years .Thyrocare, a group of companies with primary objective to promote the applications of RIA in laboratory medicine, believes that the increasing
awareness of RIA is the first step in its endeavor. Thyroidology is the major beneficiary of this analytical tool. Using this mass-processing concept,
Thyrocare has already established the availability of this service and it has been observed the knowledge of the technology has been far below the
desired level. The below given information focuses on the principles, procedures, applications, quality control, cost factors and training in RIA.We
will be pleased to provide more information on request in various aspects of radio immunoassays, Thyroid function tests, Thyroid disorders and their
diagnosis, Applications of Radioisotopes in Thyroidology (Diagnosis and Therapy).
What are Radio immunoassays?
"Radio immunoassays" (RIA) are simple, reliable and reproducible laboratory techniques used extensively in clinical laboratories for the last three
decades world wide. This Nobel prize winning technique is based on the antigen-antibody reaction, imparts the highest degree of specificity, and
utility of radioisotopes offers astonishing degree of sensitivity.They are primarily utilised in diagnosis and management of thyroid disorders and
What is the principle of RIA?
As the name suggests there is an antigen - antibody reaction between the antigen (Hormone) of interest and its specific antibodies raised from
laboratory animals. The quantum of antigen-antibody binding is monitored using a radiolabelled antigen or antibody. In brief the RIA kit contains
test tubes which have been coated with the antibody. To these tubes, standards or samples are added (usually 25 to 200 ul volume) along with the
tracer, The contents are incubated for 1 - 2 hours and the tubes are emptied by decanting the contents or aspirating. The tubes are washed with
the wash solution provided and are counted in a gamma counter. The counts obtained for various known standards used in the assay are utilised for
generating a dose - response curve and the unknown concentration in serum samples are extrapolated from the data.
How many types of RIA are there?
Basically there are two types and they are: a limited antibody assay (RIA-original) and an excess antibody assay (IRMA - also called RIA).
For e.g. T3 and T4 are done using the conventional RIA while the estimation of TSH, FSH, LH and PRL are using IRMA. All the pituitary hormones are done
with IRMA which has got a wider working range, improved sensitivity and shorter incubation time.
What are other immunoassays?
It is RIA which is mother of all other immunoassays. Many non-isotopic labels have been tried for the last 30 years,they include ELISA
(enzyme as marker), Chemiluminescence, fluorescence and others.Many of them though claimed to be better than RIA in certain aspects, none of them really
could replace RIA in large scale. Some of them are costly, some less reproducible and some both.
What is an RIA kit?
It is an user friendly pack of reagents sufficient for 100, 200 or 500 estimation and in them all the required reagents are provided along with a
protocol or product insert which contains the details of the procedure, reagents and applications.
How long can one use RIA reagents?
The radioisotope used in RIA kits is I-125, which has a half life of 60 days and with a gamma counter of good efficiency, some of the RIA kits can be
used as long as 90 days. For some delicate proteins however the utility is limited to 4 to 6 weeks. It is important to store the reconstituted reagents
as directed and should avoid freezing and thawing.
Is it harmful to use RIA kits since they contain radioactivity?
No, because the dose handled is very little in quantity and that too they are not administered internally. The vials if they are kept a feet away, their
effects are not experienced by the users. Some data of Radiation Physicists reveal that an X-Ray technician receive much larger dose than an RIA
technician. Comparatively the concentrated acids used in ELISA could prove to be much more dangerous.
What are the parameters utilized in calling a kit better?
Primarily the reproducibility (precision, accuracy, recovery, sensitivity and parallelism) of a kit, is the major factor for the superiority of the kit
while many give importance to simplicity and cost factors; and a pathologist should remember that all claims made by any kit manufacturer is to sell