Medical Research: What are the main findings of the study?
Dr. Pathak: Cervical testing for human papillomavirus (HPV) is being piloted as a more accurate method for cervical cancer screening than current cytology-based (“Pap smears”). However, cervical testing still requires gynaecological examination and a doctor or nurse to take the sample. This could be a deterrent to attending screening as it is invasive and time-consuming. Urine-based HPV testing would be a less invasive and more convenient alternative.
Our study was completed at the Queen Mary University London Women’s Health Research Unit. We pooled the results of 14 studies from around the world which tested 1443 women for HPV in urine and cervical samples. We found that detection of HPV in urine seems to have good accuracy for the detection of HPV present in the cervix. We also found that using first void samples (the first part of the stream of urine) was twenty-two times more accurate than random or midstream urine samples.
Medical Research: Were any of the findings unexpected?
Dr. Pathak: Among the 14 studies that we included in our analysis, there was a large amount of variation between individual results. We statistically analysed different factors that could explain these differences, including the use of different commercial testing methods, the presence of other conditions such as HIV and the average age of participants. However, we only identified only one reason for this variation: first-void urine samples were more accurate than random or midstream. The contribution of the type of urine sample collected is not entirely unexpected as first-void urine samples have higher levels of DNA which make it easier to perform the laboratory tests required to detect HPV. Nonetheless, we were surprised that other factors did not explain any variation. This could be due to the size of the population tested and we expect that when larger numbers of women are tested other reasons may become evident.
Medical Research: What should clinicians and patients take away from your report?
Dr. Pathak: Urine-based testing of HPV should be considered as an accurate and convenient alternative to cervical sampling. However, our results must be interpreted with caution for several reasons.
- Firstly, we were unable to fully explain the difference in accuracy found between individual studies.
- Secondly, there is no standardised and reproducible method of this type of testing. This would be essential to ensure that the results are consistent and reliable when used I outside the world of research.
- Thirdly, our study only looks at whether the urine-based test is good at identifying the presence of HPV. It does not look at whether the detection of HPV in urine predicts the presence of cervical cancer, cervical pre-cancer, or abnormal smear tests. This is a crucial difference as the effectiveness of predicting cervical cancer or pre-cancer will determine how many lives this test could save.
When these factors are addressed, it may be possible to incorporate urine-based testing into routine clinical practice.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Pathak: Our recommendations aim to make the test more consistent and to ensure that it can accurately detect cervical diseases. Specific points include:
- The standardisation of urine-testing methodology.
- The prediction of cervical cancer or pre-cancer, and a comparison to the smear test as a method of identifying cervical disease.
- The appropriate management of results that detect HPV and safe lengths of time between tests that do not detect HPV.
- The cost-effectiveness of including this test as part of routine screening.
Our research unit will remain active in this research area and we hope that our paper, published in the BMJ this week, will stimulate an international effort to prioritise urine-based testing for cervical cancer screening.
Accuracy of urinary human papillomavirus detection for viral surveillance and cervical cancer screening: systematic review and meta-analysis