Gynecologic Cytopathology (Pap Smears)
Gynecologic cytopathology, popularly known as the Pap Smear test, was first developed by and named for Dr. George Papanicolaou in the 1920’s to detect cancer of the uterine cervix and its precursors. Before the Pap Smear, cervical cancer was one of the leading causes of cancer death in women. Over the years, the widespread use of this test in developed countries has reduced cervical cancer to a relatively rare disease. Thus, the traditional Pap Smear test is the greatest cancer prevention story in the history of medicine.
Traditionally, after a Pap smear is obtained from a patient it is smeared directly onto a glass slide and sent to a cytology laboratory where it is stained with special pigments and prepared for examination. Cytotechnologists, specially trained professionals who screen cells under a microscope, identify and marks any abnormalities. Smears deemed abnormal are then reviewed by a pathologist who renders a diagnosis and recommendation for treatment and/or further tests if necessary. This process, augmented by strict quality controls including directed and random review of smears deemed normal and repeated year after year results in a test which, relative to other tests in medicine, is highly accurate.
Pap Smear Technologies offered by OPA
Recently, attention has been directed at the rare cancers missed by the highly accurate traditional Pap smear test. No test in medicine is perfect or ever will be; however, this attention has led to the development of new technologies intended to reduce the risk of missing this potentially fatal cancer.
The Liquid-Based Pap Smear
In contrast to the traditional Pap smear in which the specimen is immediately smeared directly onto a glass slide, in these proprietary technologies the specimen is instead transferred to a collection fluid. The cells of interest then undergo an automated process which concentrates the cells of interest while removing obscuring material, blood and excess inflammatory cells. An enriched, representative portion of the cells is then deposited in a uniform thin layer onto a glass slide for evaluation by the cytotechnologist.
The advantages of liquid-based technologies over conventionally obtained Pap smears include a decrease in unsatisfactory and limited samples, resulting in fewer patient callbacks for repeat sampling and associated patient anxiety.
Explanations for this include:
1) all of the cervical sample is submitted to the laboratory,
2) the possibilities for technical errors at the time of the patient examination are reduced, and
3) the enrichment process can remove obscuring material.
In addition, the uniform thin layer of cells on the slide is in many ways easier to view and interpret under the microscope than a conventional smear. Special additional studies can also be conveniently be performed on the specimen obtained for the Liquid Pap smear (see Ancillary Molecular Diagnostic Testing below).
Disadvantages of proprietary liquid-based Pap smears include significantly greater cost, environmental impact of increased disposables, and the loss of some spacial features that are present in a traditional, directly prepared smear. Some studies have reported higher reporting of abnormal results when no abnormality was actually present.
OPA offers both SurePath and ThinPrep technologies
Computer-assisted screening refers to automated Pap smear analysis devices. Utilizing high-speed video technology and image interpretation, theses machines are designed to identify those slides most likely to contain abnormalities and marks them for further human review and interpretation. These machines may enhance traditional manual evaluation of cervical cytologic specimens by reducing the number of significant abnormalities missed. The system employed by OPA (FocalPoint Primary Screening System) is approved by the federal Food and Drug Administration for primary screening of Pap smears. Pap smears determined by the machine to be most likely to have significant abnormalities are reviewed by expert cytotechnologists and then, when appropriate, by our board certified MD cytopathologists who make the final diagnosis. In addition, any smears identified as originating from clinically “high risk” patients receive automatic review by the machine, a cytotechnologist, and an MD cytopathologist.
The FocalPoint system enhances traditional manual review by addressing the problem of errors in recognition of potentially abnormal cells. It allows our cytotechnologists and pathologists to devote more time to those slides most in need of review. Also, unlike a human, it can operate 24 hours a day immune to eyestrain, fatigue and distractions, all of which could lead to test errors. Unlike other computer-assisted screening devices, the FocalPoint system requires no special collection devices and is designed and approved to analyze conventionally obtained Pap smears as well as one of the available liquid-based Pap smear technologies (SurePath).
Ancillary Molecular Diagnostic Testing
Human Papilloma Virus (HPV)is the cause of nearly all cervical cancer. Recent studies suggest that judicious use of the technologies that can detect HPV and its high risk subtypes in conjunction with the Pap smear can result in the detection of slightly more cancers and serious pre-cancers than can the Pap smear alone (algorithm).→. There are many tests for this virus on the market, but the most significant research results showing this benefit have utilized Hybrid Capture 2 (HC2). This test can be performed using a special cervical swab or, conveniently, using the same fluid from a liquid-based Pap smear.
OPA also offers testing for infections from Chlamydia and Gonorrhea. This test can also be performed on liquid-based Pap smear specimens submitted to our laboratory. As will always continue to be the case, there is no technological solution to prevent all false negative Pap smears at the 100% level. Even with the assistance of the machines and special tests described above some cancers will be missed. That is why periodic expert physical examination, history, and Pap smears of any type performed at recommended intervals with evaluation by qualified, experienced MD cytopathologists remain the most important components of cervical cancer prevention.