Featured Research

from universities, journals, and other organizations

Suspect strep throat? Re-check negative rapid test results with lab culture

Date:
May 28, 2014
Source:
University of Washington
Summary:
Clinical guidelines for diagnosing strep throat in teens and adults differ, as do physician practices. A recent study supports guidelines that mandate confirming negative rapid test results with a lab culture when a patient has symptoms that suggest a bacterial infection. The rapid test detects certain antigens, one of the body's efforts to fight off strep bacteria. Attempting to grow bacteria from a throat specimen double checks for the presence or absence of Group A Streptococcus bacteria, as well as a few other bacterial infections, and could help avoid both under-treating and over-treating sore throats.

A man has his throat examined.
Credit: Clare McLean

Clinical guidelines conflict on testing teens and adults whose symptoms point to a possible strep throat. A chief contention is whether negative tests results from a rapid analysis of a throat swab, done in a doctor's office, should be confirmed through a follow-up laboratory culture.

Related Articles


The rapid test detects certain antigens, one of the body's efforts to fight off strep bacteria. Attempting to grow bacteria from a throat specimen double checks for the presence or absence of Group A Streptococcus bacteria, as well as a few other bacterial infections.

A study published May 27 in Clinical Infectious Diseases indicates that performing a laboratory culture could help doctors and patients avoid both under-treating and over-treating sore throats.

Several guidelines on diagnosing and treating Group A Streptococcus sore throats in adults have been published by medical and scientific professional societies, including the College of American Pathologists and the Infectious Diseases Society of America.

The study findings call into serious question clinical guidelines that rely only on the rapid test, according to Dr. Ferric Fang, professor of microbiology and laboratory medicine at the University of Washington, and senior author of the paper.

Fang said, "Each year nearly seven million Americans seek medical attention for a sore throat, making it one of the most common reasons to see a doctor."

About one in 10 of these patients has a strep throat. The rest are due to viruses or other causes. Although most cases of strep throat heal on their own, antibiotic treatment reduce symptoms decrease transmission to others, and can prevent rare but serious complications such as damage to heart valves.

Accurately diagnosing that the sore throat is not bacterial is also important, Fang said. Antibiotics for a strep throat don't work against a viral sore throat, and can produce harmful side effects not outweighed by benefits. Unnecessary use of antibiotics also contributes to antibiotic-resistance.

Fang explained that rapid tests, while convenient, miss up to 1 out of 4 cases of strep throat. Some physicians will recommend a throat culture even when the rapid test is negative, if the patient's symptoms seem to warrant it.

Doctors check a patient with a suspected strep throat for tender glands in the neck below the ears, lack of a cough, difficulty opening the jaw, painful swallowing; oozing, swollen, tonsils; fever and a high white blood cell count.

Despite the constellation of suspicious symptoms in the Centor score for strep throat likelihood, it is still difficult to distinguish a viral sore throat from a strep throat. However, if doctors depend simply on symptom presentation to diagnose, without any testing, the tendency is to over-prescribed antibiotics. Doctors who rely just on the rapid test may end up undertreating strep throat.

The controversy on diagnosing strep throat prompted Fang and his UW colleagues, Dr. Tanis Dingle, senior fellow in laboratory medicine, and Dr. April Abbot, assistant professor of laboratory medicine and director of clinical microbiology at UW Medicine, to review the anonymous records of more than 25,000 teens and adults seen for sore throats at Harborview Medical Center and University of Washington Medical Center in Seattle. The records went back 11 years. The researchers found that more than 1,000 patients whose rapid throat cultures were negative actually turned out to have strep in their laboratory throat cultures.

"These cases would have been undetected if their doctors hadn't performed cultures," Fang said.

Most of these patients had moderate to severe symptoms; a very few had serious complications such as a tonsil abscess or rheumatic fever. Most of the patients were given antibiotics. The throat cultures, Fang said, helped guide treatment decisions in half of the cases.

From their results, the researchers extrapolated that, each year in the United States more than 250,000 patients with strep throat would not receive beneficial treatment if doctors followed those clinical guidelines that advise relying on the rapid test alone. The findings support those guidelines that mandate back-up lab cultures.

The researchers concluded, "Appropriate use of rapid and culture-based diagnostic tests can reduce inappropriate use of antibiotics for sore throats, while avoiding under-treatment of patients who can benefit from antibiotics."


Story Source:

The above story is based on materials provided by University of Washington. Note: Materials may be edited for content and length.


Journal Reference:

  1. T. C. Dingle, A. N. Abbott, F. C. Fang. Reflexive Culture in Adolescents and Adults with Group A Streptococcal Pharyngitis. Clinical Infectious Diseases, 2014; DOI: 10.1093/cid/ciu400

Cite This Page:

University of Washington. "Suspect strep throat? Re-check negative rapid test results with lab culture." ScienceDaily. ScienceDaily, 28 May 2014. <www.sciencedaily.com/releases/2014/05/140528163826.htm>.
University of Washington. (2014, May 28). Suspect strep throat? Re-check negative rapid test results with lab culture. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2014/05/140528163826.htm
University of Washington. "Suspect strep throat? Re-check negative rapid test results with lab culture." ScienceDaily. www.sciencedaily.com/releases/2014/05/140528163826.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
Today's Prostheses Are More Capable Than Ever

Today's Prostheses Are More Capable Than Ever

Newsy (Nov. 26, 2014) Advances in prosthetics are making replacement body parts stronger and more lifelike than they’ve ever been. Video provided by Newsy
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Newsy (Nov. 25, 2014) Need another reason to eat yogurt every day? Researchers now say it could reduce a person's risk of developing type 2 diabetes. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins