Liquid cytology is a cytopathology technique in which specimens are prepared in a fluid rather than being mounted directly onto a slide. One common application for liquid cytology is in Pap smears used to check women for signs of changes in cervical health. Several governments have researched this technique and have returned varying reports on how effective it is. Some believe that it is equivalent to other techniques and can in fact be better, while others warn that it can increase the risk of false positives.
Cytopathology in general is the study of tissue on a cellular level for the purpose of learning why someone is sick, or for conducting screenings to determine whether or not someone is experiencing cellular changes. It is sometimes called “cytology” even though this word is actually a generic term which just means “the study of cells,” and does not focus specifically on the examination of cells for disease. Cytopathologists work in hospitals, independent diagnostic labs, and field research centers all over the world.
In the case of liquid cytology, when a sample is collected, it is immediately placed in a preservative fluid. There are several ways to do this. One popular method involves the use of a breakaway swab. The sample is collected on the swab, the swab is inserted into a container of preservative fluid, and the handle is snapped away so that the container contains just the head of the swab. People can also rinse swabs with preservative fluid, lifting the cells from the swab and depositing them in a specimen container.
Once the liquid cytology sample reaches the lab, it can be spun to remove impurities and then used for a representative sample which can be studied under a microscope. One advantage of liquid cytology is that there is less concern about specimen sizes and wastage; if a mistake happens, the technician or pathologist still has the original sample. This reduces the risk that a patient will need to be swabbed twice to collect a sample for study.
One disadvantage of liquid cytology, however, is that this diagnostic technique can sometimes yield false positives. This can be a concern when a positive will lead to more invasive testing and medical procedures. For this reason, the liquid cytology technique is not always recommended for pathology screenings. Pathologists usually learn how to process many different kinds of samples while they are in training, and part of their education includes learning how to minimize the risk of false positives. As a general rule, false positives are considered better than false negatives, because a false negative could result in a missed diagnosis and danger for the patient.
