What tests are used to diagnose sinusitis?

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Sinusitis is caused by infection and inflammation of the inner linings of the sinuses. Diagnosis is commonly made by the physician on the basis of clinical symptoms of the condition.

In most cases there is a predisposing viral infection that leads to nasal blockage or runny nose along with pain over the face (over the cheek bones, behind the yes and over the forehead) and there may be a reduction in sensation of taste and smell.

Some people may develop other symptoms like discharge of yellowish green pus from the nostrils, fever, headache etc. 1-6

Who diagnoses sinusitis?

Referral to an ear, nose and throat (ENT) specialist or an Otolaryngorhinologist is usually made if the symptoms persist are severe or if they keep coming back.

Diagnosis of sinusitis

Diagnosis then involves a series of blood and imaging tests. These include:

• Routine blood tests. These help in detection of an infection. This infection may lead to increase in the white blood cell counts. Allergies or hay fever giving rise to sinusitis may cause rise in specific type of white blood cells called the Eosinophil.
• The ENT specialist uses a special light to examine the inside of the nose. This helps in detection of nasal polyps, nasal bony spurs, deviated nasal septum and other anatomical defects that may lead to narrowing of nasal passages and predispose to sinusitis.
• A light is shined against the sinuses. Normally the sinus appears hollow and the light shines through giving a reddish glow. When inflamed and blocked with secretions and mucus the light fails to sine through and the sinus appears opaque. This test is called the transillumination test.
• Similarly the sinus is tapped gently. A normal sinus gives a hollow sound while a blocked sinus gives a dull sound. This may be painful for inflamed sinuses.
• A X ray of all the sinuses. Normal sinuses show up as hollow black cavities on either side of the forehead, bridge of the nose, behind the yes and under the cheek bones. When inflamed the sinuses appear to be blocked with white discharge and this is visible on X rays.
• A new method of inspecting the insides of the sinuses is the fiberoptic endoscope or the rhinoscope. This is a thin flexible tube with a camera and a light at its tip. The nasal passages are lubricated with local anesthetics and the scope is passed. The inside walls and linings of the sinuses may be visualized with this instrument.
• Sinus puncture is a method of obtaining a sample of the fluid from the sinuses using a long thin needle. This helps in detection of the organism causing the sinusitis. This is not routinely practised.
• When fungal sinusitis or sinus tumors are suspected or need to be ruled out imaging studies like ultrasonography of the sinuses, CT scan or MRI scan of the sinuses may be prescribed. These also help detect anatomical abnormalities of the nose and sinuses.
• Those with allergies may be recommended allergy testing to detect the cause of allergies.
• Since persons with HIV AIDS, diabetes and other poor immunity situations are more likely to get sinusitis, blood tests for these may be recommended.
• Certain tests are available to detect if the cillary cells of the nose and sinuses are functioning adequately. Sweat Chloride tests are ordered to exclude Cystic fibrosis that predisposes to sinusitis.
• Cells of the nasal and sinus lining are taken as samples and examined under the microscope for abnormalities.
• Conditions to be ruled out in diagnosing sinusitis (because they mimic symptoms of sinusitis) include allergic rhinitis, common cold, adenoiditis in children and other causes of headaches.

Further Reading

• All Sinusitis Content
• Sinusitis - What is sinusitis?
• Causes of sinusitis
• Symptoms of sinusitis
• Treatment of sinusitis

Last Updated: Apr 19, 2019

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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