HPV testing vs Pap test in cancer screening: Cochrane Systematic review

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.