Simple sore throat may not really be simple at all

Q: I saw my doctor last week, who said I had acute pharyngitis, but didn't say what that was. It sounds serious. What is it?

A: Good news: It's rarely serious.

I know the word "acute" in front of any medical term makes it sound serious. And I know that Latin-based words like "pharyngitis" sound alien.

But acute pharyngitis simply means that your throat has become inflamed by something, usually an infection.

Acute pharyngitis causes a sore throat, one of the most common medical problems for which people seek medical care. The most common causes of acute pharyngitis are infections with bacteria or viruses.

When I was in medical school, we were taught that a patient with a sore throat had either an infection with a type of bacteria called Group A streptococcus ("strep") or with any of multiple viruses.

Group A strep was diagnosed with a throat culture and was treated with antibiotics, particularly penicillin. Since antibiotics do not work against viral infections, antibiotics were not to be prescribed except when the throat culture showed Group A strep.

So, I was taught that what a doctor did for a patient with acute pharyngitis was simple: You got a throat culture, and if it showed Group A strep, you prescribed antibiotics.

It did seem simple. The problem was that it wasn't that simple in practice.

One reason why was that the results of a culture took one to two days to come back. You had to track down the patient when the culture came back showing Group A strep, and then start treatment. To avoid the time those steps took, many doctors just prescribed antibiotics when they were pretty sure the patient had a strep throat.

The problem was that doctors weren't terribly good at making that judgment. As a result, antibiotics often were prescribed in people with sore throat caused by viruses.

Overuse of antibiotics, in turn, led to bacteria becoming resistant to antibiotics - which has now become an important problem.

The way a doctor today diagnoses and treats a patient with acute pharyngitis is not very different from the way it was decades ago. From my perspective (with which not all my colleagues agree), it should be different today.

One thing that has changed is that 70 years ago, an unrecognized and untreated throat infection with Group A strep could cause one of two serious diseases: acute rheumatic fever or acute glomerulonephritis.

The first is a condition that can damage the heart valves, and the second can damage the kidneys. Early diagnosis and treatment greatly reduced the chance that these diseases would develop. Today, however, the Group A strep that are circulating in the United States are much less likely to cause these diseases.

But the chance of side effects from the treatment - antibiotics - is not reduced. Penicillin can cause side effects ranging from a bad rash to a life-threatening drop in blood pressure. A doctor never wants to prescribe a treatment when its risk is worse than the risk from the disease.

If a doctor knows for sure that a patient has strep throat, the value of antibiotic treatment today is still greater than the risk.

About 30 years ago, rapid strep tests were developed. The latest versions of the test are fast: Results come back within 15 minutes. And the tests appear to be highly accurate in detecting Group A strep. So this seemed like a major advance.

But, again, it's not that simple. First, the rapid tests are quite accurate, but not perfect. Second, we've learned that other kinds of strep besides Group A strep, and other kinds of bacteria entirely, can cause acute pharyngitis. The rapid strep tests don't detect any of these bacteria. Admittedly, we don't yet have solid evidence of the value of treating these bacteria.

Third, sometimes Group A strep live in our throat without causing any disease: There is no value in killing those strep. Finally, even when we test for all known bacteria, viruses and other microbes, we still can't find a cause of sore throat in about 30 percent of patients.

So there's still a lot to learn about a medical problem that causes more days lost from work than all labor disputes combined.

• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.