Dear Tomas,

For Renin activity assessment there is a common way in all assay types.

Angiotensinogen converts to AngI by Renin activity.

Conversion of AngI to AngII and degradation of AngI inhibit by ACE inhibitors and protease inhibitors such as PMSF respectively.

Now, AngI will determin using various type of Methods such as Chromatography (e.g HPLC), LC-Mass or Immunoassays (RIA, IRMA, ELISA, ECLIA,...).

LC-Mass or Mass-Mass are very sensitive and specific, but very expensive too.

HPLC has lower sensitivity, good specificity but it is time consuming and more expensive than routing immunoassay.

RIA has lower specificity than IRAM and ELISA (sandwich type) and ECLIA.

IRMA and ELISA have almost same sensitivity and are more sensitive than RIA.

ECLIA is more sensitive than IRMA and ELISA too.

below links are helpful, I hope.

http://www.aacb.asn.au/documents/item/733

http://jnm.snmjournals.org/content/13/11/806.full.pdf

http://www.alpco.com/pdfs/11/11-RENHU-E02.pdf

http://www.affinitydiagnostics.ca/pdf/_109_SO19011%20Plasma%20Renin%20Activity%20RIA.pdf

http://www.clinchem.org/content/22/2/250.full.pdf

best

mehdi