Paps and HPV testing 


 High grade lesion, licensed through Creative Commons , from Wikimedia

High grade lesion, licensed through Creative Commons , from Wikimedia

We are in a period of rapid flux when it comes to the care of the cervix. For decades, women used to sign up for the annual pap smear. It was such a well known procedure that the annual exam nearly became synonymous with it. Today all that is changing. 

The pap smear was designed to screen for precancerous and cancerous cells on the cervix. It did so by actually wiping off a few surface cells for placement on a slide, fixation, dying, and inspection. An experienced tech could get a rough idea of the health of the tissue. But this test was insensitive and nonspecific. 

In the 1960's and 1970's we began to understand that cervical cancer and its precursors were caused by a virus, Human Papilloma Virus, or HPV for short. This is a common virus acquired through sexual contact.  Certain subtypes also cause genital warts.  Early on we could identify it indirectly and with difficulty and great expense. Nowadays, with advancements in molecular biology, DNA based tests make HPV detection easy and relatively cheap. We can even check for especially concerning subtypes of the virus. 

HPV tests.png

When, until rather recently, our tests like the pap were indirect, and results approximate, our patterns of testing were fairly conservative. This means that since we knew our tests weren't that accurate, we tried to make up for it by testing more frequently, like annually. And this largely worked. The incidence of cervical cancer has plummeted in the last half century. Now, however, that we have precise molecular genetics based methods which test sensitively and specifically for the DNA of HPV, we have been able to be far more sure of our patients' conditions and we can test less frequently. So if you have noticed articles in the popular media discussing less frequent pap smears, you now know why. 

This has made some of us a little uneasy, perhaps through force of habit.  But the good news is this: Our methods of HPV detection are not the only things that have improved. Our very methods of determining practice recommendations has evolved. In the old days, checkup schedules for screening tests were determined by experience. Now we base it on evidence, evidence about the progression rates of a disease combined with the sensitivity and specificity of our screening. Advances in molecular biology combined with increased computational sophistication have enabled us to parse out certain age groups and make much more tailored recommendations for each group. We also now discriminate based on a patient's past history and also on whether or not they are pregnant. Between all the variables, it is much more complicated than before to determine when a given woman should het her next pap and HPV test. It is so complicated in fact, that an official app has been developed, to help doctors with the process.