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medpundit |
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Friday, April 04, 2003This method is considered superior to the former method, the original Pap smear, in which the mucous and cells are smeared on a microscope slide, sprayed with preservative and shipped to the lab. The problem with this method being that sometimes the cells clump on top of one another or just get broken up in the process, making it difficult for the pathologist to properly assess their state of normality. Now comes a study from France that says the new method is inferior to the old, contrary to previously published studies. The French team compared pap smear results done by both the old and new method with biopsy results and close inspection of the cervix with a magnifying lense (called colposcopy). Both biopsy and colposcopy provide more definitive results than the screening pap smears. They found that the conventional pap smear was both better at sampling cells and better at predicting true abnormalities than the newer monolayer method. But, there is a major problem with the study. They were sloppy in the way they collected their specimens. Sloppy in a way that favors the conventional pap over the monolayer method: Each woman underwent a standard conventional smear test. The remaining material was then used to prepare the monolayer slide and for human papillomavirus testing. That means that far fewer cells were placed in suspension for the monolayer method than were placed on the slides for conventional evaluation. And, since pap smears rely on the quality and quantity of cells collected for their accuracy, it’s no surprise that the monolayer method faired worse. Fewer cells to examine equals less accuracy. And in fact, the greatest difference in the two methods was in the adequacy of specimens. Only 75 conventional paps were inadequate vs. 235 of the monolayer paps. This says it all. The authors claim that their method of sampling isn’t biased toward the conventional pap because they used a mathematical model to compare the two. But, math models are just that - models. You can’t argue with reality. And the reality is that the sampling method was biased toward conventional pap smears. A far better comparison would be between two groups of women - one of which had conventional paps, the other of which had monolayer paps. This would insure that neither method suffers from a diluted sampling of cells. posted by Sydney on 4/04/2003 09:02:00 AM 0 comments 0 Comments: |
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