world cancer report - iarc

Fig. 4.48 Women at a clinic in India participating
in a study of early detection of cervical cancer.
the liquid-based method seems to result
in more slides being classified as having
low-grade squamous epithelial lesions or
higher, which were classified as having
less severe disease by conventional
smears, than the reverse situation. The
difference in cost between liquid-based
and conventional cytology is unclear
because of substantial uncertainty about
the relative effectiveness of these two
approaches[13].
It has been suggested that improvements
in the detection of dyskaryosis (abnormal
changes in cell nuclei) using extended tip
plastic spatulas instead of the traditional
wooden Ayre’s spatula would be of
approximately similar magnitude to the
improvements which might result from
replacing conventional cytology with
liquid-based methods [14]. Automated
cytology reading systems are under development
and some health economic evaluation
has been carried out.
In view of the importance of HPV in the
etiology of cervical cancer, HPV testing to
allow women to be classified as high-risk
HPV-positive (displaying HPV types associated
with an increased risk of cervical
neoplasia) or negative (otherwise) could
be used as an adjunct to cytological
smear tests. However, the possible value
of HPV testing in the triage of women with
low-grade abnormalities is uncertain.
Alternatives to the Pap smear
HPV testing
HPV testing may be used for primary
screening. In developed countries, most
attention has been focused on HPV testing
as an adjunct to cytological screening
170 Prevention and screening
(see above), in part because of ethical and
medico-legal problems which might ensue
in conducting a randomized trial which
would involve withdrawal of the offer of
cytological screening from the group
assigned to be offered HPV testing. This
would not be the case for populations in
which Pap testing has not been introduced,
notably in developing countries.
The major issues in relation to such use of
HPV testing have been the cost of the test
itself and its relatively poor specificity
[15,16]. Poor specificity results in followup
for women without cervical disease,
incurring costs which may be more than
the society can afford. In both developed
and developing countries, the development
of primary screening based on HPV
tests might be rendered obsolete by mass
HPV vaccination (Human papillomavirus
vaccination, p148).
Visual inspection
Unaided visual inspection of the cervix by
nurses and other non-medical health
workers, also known as “down-staging”,
has been proposed for developing countries
which lack the laboratory facilities or
resources to implement cytological
screening [17]. Women with abnormal
findings require further investigation,
which entails a cytological test if appropriate
facilities are available, or specialist
medical examination if no cytology services
are available.
In view of the unsatisfactory performance
of unaided visual inspection, consideration
has been given to aiding naked-eye
visual inspection by impregnating the
cervix with 3-4% freshly prepared acetic
acid to detect acetowhite areas (Fig.
4.47). This screening approach is known
as visual inspection with acetic acid (VIA)
(synonyms are cervicoscopy and direct
visual inspection). In studies in China,
India, South Africa and Zimbabwe, visual
inspection with acetic acid has emerged
as a satisfactory screening test to detect
cervical cancer precursor lesions, with a
sensitivity ranging from 67 to 90% [14,
18-20]. This is similar to (or higher than)
the sensitivity of cytological screening,
but specificity is generally lower (range is
64-92%). Therefore, if screening based on
visual inspection with acetic acid is instituted,
a potential consequence would be
high rates of referral for further investigation.
Currently, randomized intervention
trials are in progress in India to evaluate
the cost-effectiveness of visual inspection
with acetic acid in cervical cancer screening
[21].
Addition of magnification to visual inspection
with acetic acid has not further
improved the test performance [14, 22].
Cervicography involves the taking of a
photograph of the acetic acid-impregnated
cervix to be reviewed by trained cervicographic
interpreters. Cervicography
has been found to have a lower sensitivity
than cervical cytology [14, 23], and also
reportedly suffers from high false positive
rates [24].