Question

The following is a reason for an apparent lack of benefit from a screening program:

	a.	The usual diagnosis of disease happens very late in the disease progression.
	b.	The preclinical phase of disease is very long.
	c.	The clinical phase of disease is long and usually ends with the death of the patient.
	d.	The current therapies are very effective when administered in the preclinical phase of disease.
	e.	The available treatments are not effective even when administered early in the disease progression.

Answer 1

Answer (b)  The preclinical phase of disease is very long.

Preclinical- It is the time period during the course of a disease where symptoms are not yet apparent, but the disease is biologically present. Preclinical phase concept is most widely used in the screening process of a disease. In this period virus generally remain in incubation period (they multiply in numbers in the host and patient doesn't show symptomes but he can infect others), so at the time of screening patient do not give any symptomes and pass the screening test.