A negative
HPV test is more reassuring than a negative Pap test, as the cytology screening
has a higher chance of being false negative thereby missing some women with precancerous
lesions and delaying treatment says the result of a Cochrane Systematic review published ahead of print.
Since
decades the usual method of screening for cervical cancer is based on cell
cytology, but since the etiological relationship between cervical cancer and
HPV infection was confirmed along with advent of HPV testing in 1999, the
supremacy of these two tests is debated.
Some
physician advice Pap and HPV both, especially for women over 30 years old, who
are most at risk of cervical cancer, getting both tests provides the best
assurance of finding cervical disease before it becomes cancer.
Younger
women (20-30) are advised to get HPV test only if their Pap smear looks
"inconclusive" or "borderline.”
This
systematic review by Cochrane was aimed at determining efficacy of the two tests
in detecting precancerous lesions (CIN 2+ and CIN 3+). Literature search for
relevant studies till November 2015 identified about 40 studies amounting to a
total of 140,000 women between 20 to 70 years old who underwent cervical cancer
screening.
Data
analysis identified true positives (TP), false positives (FP), true negatives
(TN), and false negatives for each screening test (HPV test and cytology) used
in each study.
It was seen
that HPV test was more sensitive than conventional Pap test and liquid based
test in identifying CIN 2+ and CIN 3+, but less specific than Pap test in
detecting precancerous lesion.
Data
analysis showed that for every 1000 women screened, around 20 women will have
precancerous lesions. If HPV test is used, it will correctly identify 16 of the
20 women to be positive for the lesions (but will miss 4 women who have the lesions).
The Pap test will correctly identify 12 of the 20 women (but will miss 8
women).
Similarly, for
every 1000 women screened, there will be 980 women who will not have
precancerous changes. The HPV test will correctly identify 879 women as disease
free (but 101 women will be incorrectly told that they have a lesion). The Pap
test will correctly identify 951 women (but 29 will be incorrectly told that
they have a lesion).
This high
false positive rate of HPV testing will lead to high unnecessary referrals and
further tests like colposcopy, biopsy and surgery but at the same time it will
also identify 50% more women with precancerous changes as compared to conventional
cytology.
The authors
concluded that,” Whilst HPV tests are less likely to miss cases of CIN 2+ and
CIN 3+, these tests do lead to more unnecessary referrals. However, a negative
HPV test is more reassuring than a negative cytological test, as the
cytological test has a greater chance of being falsely negative, which could
lead to delays in receiving the appropriate treatment.”
Source: Koliopoulos G, Nyaga VN, Santesso N, Bryant A, Martin-Hirsch
PP, Mustafa RA, Schünemann H, Paraskevaidis E, Arbyn M. Cytology versus HPV
testing for cervical cancer screening in the general population. Cochrane
Database Syst Rev. 2017;8:CD008587. doi: 10.1002/14651858.CD008587.pub2. PMID:
28796882
Access the
abstract here.
