This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Modern diagnostic aid to diagnose ectopic pregnancy: 
Select and explain. 
A. hCG, B. Transvaginal USG, C. AFP, D. Gravindex
A: hCG
Answer: A: hCG 
Explanation: When diagnosis is in doubt a serum beta hcg is done .The advent of radioimmunoassay has allowed for very accurate quantification and is able to detect 1 IU /L .(refer pgno:159 sheila 2 nd edition)