Hcg can be estimated earliest by :: (A) Radioimmunoassay, (B) ELISA., (C) Radioreceptor assay, (D) Bloassay
Answer is A. Radioimmunoassay is more sensitive and can detect ss subunit of hCG up to 0.002 IU/ml in the serum. It can detect pregnancy as early as 8-9 days after ovulation. Reference:DC Dutta's Textbook of obstetrics,8th edition,page no:76<\p>