Which of the following techniques are used for early diagnosis of diseases?

(A). Urine analysis
(B). PCR
(C). ELISA
(D). Recombinant DNA technology (RDT)

Choose the correct answer from the options given below:

(B), (C) and (D) only

The correct answer is Option (4) → (B), (C) and (D) only  

Early diagnosis and understanding the pathophysiology of a disease are crucial for effective treatment. Conventional diagnostic methods, such as serum and urine analysis, may not always lead to early detection. However, modern techniques like Recombinant DNA technology, Polymerase Chain Reaction (PCR), and Enzyme Linked Immuno-sorbent Assay (ELISA) have proven effective in achieving early diagnosis.

Typically, the presence of a pathogen (bacteria, viruses, etc.) is suspected only after disease symptoms have manifested. By this time, the pathogen concentration in the body is already high. However, PCR, a sensitive molecular technique, enables the detection of even low concentrations of pathogens before visible symptoms appear. PCR has become a routine tool in diagnosing HIV in suspected AIDS patients and identifying mutations in genes among suspected cancer patients. Moreover, PCR is a valuable technique for identifying various genetic disorders.

ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.