Visual Inspection with Acetic Acid for Cervical Cancer Screening
Visual Inspection with Acetic Acid for Cervical Cancer Screening
abstract & commentary
Source: Chirenje ZM, et al. University of Zimbabwe/JHPIEGO, Cervical Cancer Project.
Synopsis: In areas where Pap smear screening is not possible, visual inspection of the cervix with application of acetic acid may be a useful screening test.
There are many areas of the world in which Pap smear screening is not available and will likely never be introduced. System resources that are taken for granted in developed countries, such as the ability to transport specimens to a laboratory, the ability to communicate an abnormal result to the patient, and adequate personnel to perform the test, often do not exist in these areas. In response, alternate means of screening for cervical neoplasia have been studied.
This article reports the results of the use of naked-eye, visual inspection of the cervix after the application of diluted acidic acid (VIA) to detect cervical neoplasia. Chirenje and colleagues chose a cross-sectional design with two phases. Study participants were limited to nonpregnant women with no prior history of cervical cancer or hysterectomy, and ranged in age from 25 to 55 years. In the first phase, both cytology screening (performed only with an Ayres spatula) and VIA were performed. Abnormal VIA or Pap smear reports resulted in the woman being scheduled for colposcopy. In phase II of this study, women also received both Pap smear screening and VIA, but all were requested to have a colposcopic examination.
The results of the colposcopic examination were taken as the reference standard. When clinically indicated, biopsies were obtained. Chirenje et al stratified disease detection as low-threshold or high-threshold disease, depending on whether LGSIL or HGSIL was detected. Chirenje et al did not consider atypical squemous cells of unknown origin (ASCUS) or atypical glandular cells of unknown origin (AGUS) Pap smear results as positive.
Appropriate quality control measures were used for evaluation of the cytology specimens.
Twenty percent of the women in phase I had a positive VIA, and 40% had a positive VIA in phase II. Fifteen percent and 13% of the Pap smears were positive in the two study phases. In phase II of the study, the positive predictive value of VIA was 19%, and 33% for the Pap smear. The sensitivity of VIA to detect high-threshold lesions was 77%, and 44% for the Pap smear. However, specificity of VIA was only 64%, whereas the Pap smear sensitivity was 91%.
In the discussion section, Chirenje et al suggest that VIA may be a reasonable method of detection of cervical neoplasia in areas of the world where Pap smear screening is not available.
Comment By Kenneth Noller, MD
This is an important article on which I have received numerous questions. Several of the primary care providers in my area have asked me whether they should be performing VIA rather than Pap smears since, according to this article, it is more sensitive. The individuals who ask these questions completely miss the point of the article and fail to recognize its many shortcomings. I chose this article for review because I expect a number of readers of this publication will be asked similar questions. Let me point out a few important facts.
First, Chirenje et al never suggest in their article that VIA should supplant cytology in areas of the world where cytology screening is available. The record of cytology is simply too good. Cervical cancer has become an extremely rare disease in countries such as the United States where widespread Pap smear screening is in practice. Indeed, cervical cytology screening is the single best cancer detection method ever devised.
Second, this study used a suboptimal method of performing cytology screening. Only a wooden Ayres spatula was used to collect the sample. Numerous articles have shown that the addition of an endocervical cytology screening device (such as an endocervical brush) approximately doubles the detection of cervical neoplasia. Thus, this article has a methodologic flaw and is biased against cervical cytology. It is likely that the differences between VIA and cytology in the detection of cervical neoplasia would have been considerably less if a proper collection technique had been used.
Third, in phase II of the study, the nurse midwives performing the VIA test knew that all patients would have colposcopy. It is likely that this knowledge (bias) was the cause for the doubling of the rate of positivity of the VIA test in phase II. Such "overcalls" automatically increase the sensitivity of VIA, while reducing its specificity.
Fourth, while Chirenje et al briefly mention that "the observed high number of false-positive results for VIA may lead to high rates of referral, " they also state that "VIA could be an acceptable means of screening for cervical cancer" I believe they have underplayed the high rate of false-negative VIA results. I find it difficult to believe in a cervical cancer screening test that results in 40% of the patients having a referral for colposcopic examination. Only because of the difficulty with communication in less-developed countries where VIA might be introduced, and because of the delay between colposcopy and biopsy reports, is it worth considering. If used in the United States, it is likely that many of the women referred for colposcopy who did not have disease would be managed with a "see and treat" approach. This would result in many women without disease being treated.
Fifth, I wonder why Chirenje et al considered AGUS Pap smear reports to be "test-negative." We know from an ever-increasing number of published series that among high-quality cytology laboratories, an AGUS report on a Pap smear is associated with invasive cancer approximately 10% of the time.
There are many shortcomings in this manuscript. Therefore, I urge everyone to recognize that VIA has never been intended as a technique for use in countries where cervical cytology screening is widespread. An additional concern is the low specificity of the test results in a high percentage of women being referred for colposcopy and biopsy, most of whom do not have disease.
Visual inspection of the cervix after the application of acetic acid may be an appropriate screening test in which of the following settings?
a. Affluent suburbia
b. U.S. inner city
c. Rural Zimbabwe
d. STD clinic
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