Negative Strep Throat Test: What Else Mimics Strep?

Strep is a common bacterial infection, affecting around 10% to 15% of adults and 15% to 30% of children with a sore throat.

If you or your child has a sore throat but tests negative for strep, your healthcare provider will consider other conditions resembling strep, like the common cold or flu, to make a diagnosis. Noninfectious causes of sore throats, like allergies or acid reflux, will also be considered.

This article will review various illnesses that mimic strep throat. It will also discuss the chances of a false negative strep test and the following steps to take.

Conditions That Mimic Strep

Strep throat causes pharyngitis, the medical term for an inflamed or sore throat. The throat pain associated with strep usually comes on suddenly and worsens when swallowing or talking.

Other symptoms of strep throat are:

• Fever
• Swollen glands in the front of the neck
• Red and swollen tonsils
• White patches (pus) may be seen on the tonsils
  

Several conditions, both infectious and noninfectious, can mimic strep.

Viral Infections

Even though strep is relatively common, especially in children, viral infections are the most common cause of sore throat in all age groups.

Viral illnesses that resemble strep include:

• The common cold is caused by one of many viruses, with rhinovirus being the most common. Symptoms include sore throat, runny/stuffy nose, cough, and mild fever.
  
• Influenza is caused by infection with the flu virus. It's generally a more severe illness than the common cold, causing a high fever, sore throat, headache, muscle aches, fatigue, and weakness.
• Mono (mononucleosis) is caused primarily by the Epstein-Barr virus (EBV). Adolescents and young adults are the most commonly affected. Symptoms include extreme tiredness, severe sore throat, fever, body aches, and swollen lymph nodes in the back of the neck.
• Acute HIV syndrome may occur two to four weeks after infection with the human immunodeficiency virus (HIV). Possible symptoms include fever, rash, night sweats, muscle pain, sore throat, unusual tiredness, swollen lymph nodes, and mouth sores.
• Primary oral herpes simplex virus (HSV) infection usually occurs in childhood. Symptoms include sore throat, fever, swollen glands, and sores in the mouth and gums.
• Hand, foot, and mouth disease is caused by a coxsackievirus. It's most common in children younger than 5 years. Symptoms include fever, sore throat, mouth sores, and a characteristic rash on the palms of the hands and soles of the feet.

Other Bacterial Infections

Strep throat is caused by Group A Streptococcus (GAS). Less commonly, other bacteria can cause a sore throat. Examples include:

• Neisseria gonorrhoea is a sexually transmitted infection (STI). When the throat is infected (called gonococcal pharyngitis), fever and sore throat may occur, although some individuals have no symptoms.
• Fusobacterium necrophorum is associated with Lemierre syndrome, a rare but potentially life-threatening condition in which the bacteria spread from the throat to a large vein in the neck (internal jugular vein). Symptoms may include high fever, shaking chills, and one-sided neck swelling and pain.
• Arcanobacterium haemolyticum infection predominantly occurs in teenagers. Symptoms may include fever, sore throat with white patches on throat/tonsils, and a non-peeling rash.
• Chlamydia pneumoniae and Mycoplasma pneumoniae can cause pharyngitis. Since these bacteria can also infect the airways and lungs, a cough may also be present.

Fungal Infections

Oropharyngeal candidiasis (thrush) is a yeast infection of the mouth and throat. White patches inside the mouth and throat are a typical symptom, but there can also be redness and soreness. Although oropharyngeal candidiasis usually occurs in infants, it may occur in older children and adults (especially those using inhaled steroids or who are immunocompromised).

Treatment usually includes topical or systemic antifungal therapy.

Noninfectious Conditions

Noninfectious causes of a sore throat include:

• Allergies occur when a person's immune system reacts to a typically harmless substance, like dust or pollen. With allergies, a person may produce excess mucus in the nose. The mucus can then drip down the throat (postnasal drip) and cause a tender or itchy sensation.
  
• Gastroesophageal reflux disease (GERD) occurs when acid from the stomach flows back up the esophagus. The acid can irritate the throat, causing a burning sensation.
• Irritants: A sore throat may develop from exposure to various irritants, including tobacco smoke, air pollutants, and dry air. Shouting or snoring can also lead to a sore throat.
• Intubation: A sore throat may occur after surgery from having had a breathing tube placed through the mouth or nose and into the airway.

What Are the Chances of a False Negative Strep Test?

The initial test performed for strep throat evaluation is typically a rapid antigen detection test (RADT). While this test is widely available and provides immediate results, research suggests it may miss around 14% of cases.

If a RADT is negative, follow-up testing with a throat culture is often recommended, especially in children and teenagers.

Results from a throat culture take longer to come back (around one to two days). However, their chances of being false negatives—results indicating there is no infection when there actually is—are much lower than for RADT. Also, a throat culture can identify other bacterial causes of a sore throat.

After a Negative Strep Throat Test: What to Do

If your strep test is negative, a healthcare provider will review your symptoms and perform a medical exam to reach the correct diagnosis.

If the cause of your sore throat is viral, antibiotics are not warranted. They are only given for bacterial causes of sore throat.

Certain viruses, notably the flu, may require an antiviral drug (depending on your risk level for flu complications). Overall though, most viral causes of sore throat can be treated at home.

Examples of at-home therapies to ease a sore throat include:

• Drinking warm water with honey, but do not give honey to a child under 12 months old due to the risk of infant botulism.
• Taking an over-the-counter (OTC) painkiller like Tylenol (acetaminophen) or Advil (ibuprofen). Do not give aspirin to any person under age 19.
  

Other treatments for sore throat depend on the underlying cause. For instance, a healthcare provider may recommend a steroid nasal spray or an antihistamine for an allergy-related sore throat.

Likewise, a person with a sore throat from GERD may obtain relief through lifestyle behaviors (like avoiding smoking and fatty/spicy foods) and medication, such as a proton pump inhibitor.

Summary

Strep throat is a common cause of sore throat (pharyngitis), especially in children. If a strep test is negative, a healthcare provider may confirm the results with a throat culture, considering the rapid test may miss around 14% of cases.

Once strep throat is ruled out, a healthcare provider will consider other diagnoses, notably viral infections like the common cold and flu. A healthcare provider may also diagnose non-infectious causes like allergies, acid reflux, or irritant exposure based on the person's symptoms.

Treatment of a sore throat is tailored toward the root cause. Strep throat requires an antibiotic; however, most viral cases clear up on their own and can be managed at home.