Re: Group B Strep: 1 More Question Dr. McIntosh

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The problem is that this is one of the most common bacteria in humans (better than 30% of all women have it in their vagina), and yet the incidence of infection of the newborn is extremely small. However, the consequences of that rare infection are all too frequently catastrophic.

So, let' say that you have the test. There are 4 possible outcomes to the test.

1. You have GBS and the test tells us that you do (a true positive result). You will then be treated in labor with a penicillin based antiobiotic, and this will significantly reduce the already low incidence of neonatal GBS infection, though it does not reduce the risk to 0. So we will treat 3 women in 10 to reduce the incidence of a disease that occurs in about 1/1000 live births. Some of those women will have an allergic reaction to the antiobiotic, not many, but some. A very, very few will die of that reaction.

2. You have GBS, and the test tells us that you do not (a false negative result). This is actually the pretest status quo, you get treated based on risk factors alone, but there is a false sense of security.

3. You do not have GBS, and the test tells us that you do not (a true negative result). Again, you will be treated based on risk factors alone, but your risk of neonatal GBS is still not 0, though it is close.

4. You do not have GBS, but the test tells us that you do (a false positive result). This is the rarest possible outcome of the test. You would be treated in labor, reducing your risk of neonatal GBS not one whit (since your risk was practically 0 to start with), but with the same risk of medication allergy.

As you can see, this is not a cut and dried proposition. There are a lot of factors to consider. My two younger sons have both been born during the time that these protocols were in force, and my wife and I elected not to have testing, but to treat on risk factor alone. This not the correct answer for everyone, but we were comfortable with it, and it is the way that we manage out patients. If you cannot sleep for fear of GBS, then by all means, have the test, and stop worrying about it.

--
William D. McIntosh, MD, FACOG
Clarksville, TN

This is for educational purposes only, and is not intended to be replacement
or substitute for consultation and examination by an appropriate medical
professional.  Due to time constraints, private e-mails cannot be answered.

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