We understand from the passage that screening tests ----.

The importance of early detection of deafness in
childhood is generally recognized. Detection is
normally a two-stage process of which the first is
a screening test of hearing. Screening tests sift
out children with impaired hearing from those with
normal hearing and can be successfully
administered at any time after the age of seven
months. Children who fail a screening test are
given a diagnostic test, as the second stage in the
process, to determine the nature and extent of
their hearing loss. Both screening and diagnostic
tests must be appropriate to the developmental
level of the children to whom they are
administered. Special techniques for testing
babies and young children have been evolved at
Manchester University. When deafness has been
diagnosed, parents are advised to seek guidance
about the management and early training of their
children at the audiology clinics established by an
increasing number of local authorities and
hospitals.