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Alternative to Pap Test does not appear to
be better For detecting Cervical Cancer
Newswise — A Dutch
study that included nearly 90,000 women
finds that liquid-based cytology, a commonly
used alternative to conventional Pap tests,
is not superior to Pap tests for the
detection of cervical cancer precursors or
cancer, according to a study in the October
28 issue of JAMA.
Due to false-negative
and false-positive test results, the
papanicolaou (Pap) test is considered
suboptimal. For the liquid-based cytology
(use of cells), the cervical cells are
collected with a traditional sampling device
and rinsed into a vial with preservation
solution rather than being smeared on a
slide, according to background information
in the article. Despite numerous studies,
some uncertainty remains about its
diagnostic accuracy.
Albertus G. Siebers,
M.Sc., of Radboud University Nijmegen
Medical Centre, Nijmegen, the Netherlands,
and colleagues compared the screening
performance of Pap tests and liquid-based
cytology in terms of test positivity rates,
histological detection rates and positive
predictive values (PPVs).
The randomized
controlled trial involved 89,784 women ages
30 to 60 years who participated in a Dutch
cervical screening program at 246 family
practices. One hundred twenty-two practices
were assigned to use liquid-based cytology
and screened 49,222 patients and 124
practices were assigned to use the
conventional PAP test and screened 40,562
patients.
Patients were
screened for cervical intraepithelial
neoplasia (CIN) and were followed up for 18
months, through January 2008.
The researchers found
that the adjusted detection rate ratios for
CIN grade 1+ was 1.01; for CIN grade 2+,
1.00; for CIN grade 3+, 1.05; and for
carcinoma, 1.69. “The adjusted positive
predictive value ratios, considered at
several cytological cutoffs and for various
outcomes of CIN did not differ significantly
from unity.”
“Because of
randomization, it can plausibly be assumed
that the prevalence of CIN was equal in both
study groups.
"Therefore,
the lack of difference in detection rates
and PPV in this trial demonstrates that
liquid-based cytology is neither more
sensitive nor more specific in detecting
cervical cancer precursors than the
conventional Pap smear.”
“As shown in a previous
publication, no differences were found in
the cytological test positivity rates
between methods.
"Nevertheless,
these cytological findings contribute
insufficient evidence to claim equal
diagnostic accuracy. Both the
intention-to-treat and per protocol analyses
demonstrated that liquid-based cytology was
not superior to Pap test regarding detection
rates of histologically confirmed outcomes.
The same was found for the PPVs.
"Altogether,
these findings provide strong evidence that
the performance of liquid-based cytology is
not superior to that of the conventional Pap
test when applied within a well-organized
and quality-controlled cervical screening
program,” the authors write.
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