Is it true that VIN is more sensitive 80 % sensitivity and a 92 % specificity for VIA than Pap smear based cytology?? How helpful is “Visual based screening methods:??:--

The evidence bases in support of has emerged from several studies conducted in different developing countries demonstrating comparable or greater sensitivity of visual inspection of the cervix with naked eye than that of cytology . In addition medical as well as paramedical staff including primary health care workers can be easily trained in the visual inspection techniques in a relatively short period of time. A) By  3-5 % dilute acetic acid:-- Application of 3-5 % dilute acetic acid on the cervix during VIA results in reversible coagulation of cellular proteins. The areas with dysplasia or invasive cancer undergo maximal coagulation due to large number of undifferentiated cells in the epithelium that have a reversal of nuclear cytoplasmic ratio. Therefore these areas appear acetowhite .B) Lugol’s iodine on the cervix:--   During the VILI  procedure after application of Lugol’s iodine on the cervix the normal squamous epithelium containing glycogen takes p iodine staining mahogany brown or black . The precancerous cells and invasive cancer do not take p iodine due to lack of glycogen and appear as well defined thick mustard or saffron yellow areas .

The test characteristics of VIA have been evaluated from several cross sectional studies in India , Africa and china wherein the sensitivity range from 67% to 79 % and the specificity range from 49 % -86 % . A recently published metaanalysis reports 80 % sensitivity and a 92 % specificity for VIA . Several studies record higher sensitivity of VILI as compared to VIA however not the specificity . The sensitivity and specificity in a pooled analysis of eleven cross sectional studies were 76.8 % and 85.5 % and 85.4 % .

If results of randomised controlled trials show reduction in the disease specific mortality then that’s the strongest evidence of effectiveness of a screening test. The results of cluster randomised controlled trial in southern India after a single round of screening using VIA followed by treatment in the same visit when appropriate show a significant 25 % reduction in cervical cancer incidence and a significant 35 % reduction in cervical cancer mortality at the end of seven years of follow up . Another cluster randomised controlled trial of cervix cancer screening in Mumbai India demonstrated a significant down staging of cervix cancers in the intervention arm . Though a single round of VIA screening did not show decrease in the incidence of advanced cervical cancer and significant mortality reduction after eight years of initiation of the osmanabad trial the same may be evident after few more years of follow up .

The Mumbai cross sectional study concludes that parallel testing with both VIA and VILI should be considered where good quality cytology is not leasable and that the sensitivity of cytology and hpv testing can be significantly increased by adding the visual test. The visual inspection procedures require minimal health care infrastructure and the results are available immediately for initiating treatment at the same visit. This single visit approach is especially important to increase the programme effectiveness in the developing countries scenario with high rates of loss to follow up . Visual tests are not reliable in postmenopausal women because of changes in the transformation zone of the cervix the area in which precursors of cervical cancer arise.