Question/Statement: “My internist stated that the 'gold standard' for sarcoidosis is a bronchosomething or other--a biopsy.”

Answer: Although I am sure your internist has good intentions, the statement is not true. (see below).

Gold Standard Definition:

• In medicine, a 'gold standard test' is the diagnostic test that is regarded as definitive in determining whether an individual has a particular disease process. To meet this definition, the test must have the ability to definitively determine the presence or absence of a disease. The ‘gold standard’ is the single test that other tests are compared to.
• Of note, the term ‘gold standard’ is being replaced by ‘criterion standard test’ to mean the same thing. However, for the sake of the specific question/statement above, I will continue to use the older term.

Reasons for the answer:

• The definition of ‘gold standard’ refers to a single superior test. As you know, you can only have one best of anything. Therefore, stating that there is more than one gold standard for any disease (bronchoscopy or biopsy) is not compatible with the definition. For you Highlander (1986) fans out there, “There can be only one.”
• Secondly, there is no gold standard for Sarcoidosis. The definition of ‘gold standard’ requires that the test can definitively determine the presence or absence of a disease on its own. There are no tests for sarcoidosis that meets this criteria.
• Some people will inappropriately use the term ‘gold standard” to refer to the perceived best test. However, I would defer from this distorted definition because it is misleading. Following this erroneous rational gives a test more credit than it deserves and can lead to inaccurate conclusions.

Why is there no gold standard for Sarcoidosis?

• There is no single test to date that can definitively diagnose the disease. This is not too surprising given that the etiology remains unidentified. Even pathology samples, which are considered by many to be the best diagnostic option, are fraught with error.

Then how do you diagnose Sarcoidosis?

• Because there is no one single definitive test for sarcoidosis, the diagnosis is achieved via a combination of clinical, radiographic and histological findings.  Not every patient suspected of having sarcoidosis will need undergo risky invasive procedures. When noninvasive data is convincing enough, the diagnosis can be achieved. Obviously, this is not always the case and therefore more invasive procedures may be necessary to realize the diagnosis. I would recommend non invasive options first.

Here are a few references I found on a quick search (in regard to the specific question in red above):

“There is no “gold standard” of diagnosis but only support for the diagnosis”
http://www.baylorhealth.edu/proceedings/14_1/14_1_pierce.html

“There currently exists no gold standard to confirm the diagnosis of sarcoidosis.”
http://jem.rupress.org/cgi/content/full/203/2/359

“Owing to the absence of a diagnostic gold standard, sarcoidosis is a diagnosis of exclusion”
http://jada.ada.org/cgi/content/full/137/1/54

No single test can be relied on for a correct diagnosis of sarcoidosis.
http://www.medhelp.org/lib/sarcoid.htm

Sarcoidosis remains a diagnosis based on exclusion... A “gold standard” test to identify which patients require treatment when noncritical organs are involved would be useful.
http://www.nhlbi.nih.gov/meetings/workshops/sarcoid-wkgp.htm

Although there is no single gold standard test…
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1891789/

As there is no definitive “gold standard” for the diagnosis, sarcoidosis is essentially a diagnosis of exclusion.
http://medind.nic.in/jac/t04/i1/jact04i1p12.pdf

Question: “I recently had a chest CT and the report said I might have sarcoidosis. What is this?”

Answer:

Some background:

• Trying to understand sarcoidosis is challenging.
• Most definitions start with a statement such as, “… a chronic systemic granulomatous disease of unknown cause.” This is not too enlightening, even for physicians. This is especially unfortunate because sarcoidosis is a relatively common disease.
• Basically there are some things we know about sarcoidosis and some things we don’t know.

What is the cause of sarcoidosis?

• A single causative agent has not yet been found.  There are probably many different factors (genetic & environmental) that lead to sarcoidosis.
• Evidence suggests that sarcoidosis is caused by a heightened immune response to a yet undiscovered stimulus. Many researchers believe that this stimulus is a antigen (antigen =tiny particle of something) or a virus.
• Regardless of the causative factor, something kick starts your T-helper lymphocytes (immune cells) to get over excited. The T-cells then attract other immune cells such as mononuclear phagocytes to accumulate in specific areas and create a mass known as a noncaseating granuloma. This granuloma is the sine qua non of sarcoidosis.
• I suspect that this triggering stimulus is different in different people. Some people have an immune system that is put together in such a way that they are predisposed to an overreaction to something that is otherwise benign.  Sometimes an otherwise normal immune system will work improperly because of different factors (environment, chemicals, stress, bad luck, etc).

What does it affect?

• Being a systemic disease sarcoidosis can affect any organ. However, the lungs are the most common location. The lymph nodes, skin and eyes are also commonly affected.  Sometimes the nervous system, heart, etc is also involved.  

What are the symptoms of sarcoidosis?

• In mild cases, the disease may be asymptomatic. There is a significant amount of redundancy in most organs, and many organs will continue to work without apparent problems until the volume of disease reaches a critical mass.
• The type and degree of symptoms depends on the extent and organs affected. Usually in the sarcoidosis the organ dysfunction is caused by local tissue distortion from the mass of abnormal immune cells. If the disease resolves, then things can return to normal with little residual damage. However, if the inflammation is sufficiently high or for an extended period of time, the disease may cause permanent fibroses and loss of organ function.
• Since sarcoidosis primarily affects the lungs, the most common symptoms are related to the chest, such as dyspnea (shortness of breath), dry cough and retrosternal discomfort.
• More generalized but nonspecific symptoms include fever, malaise, anorexia, weight loss and polyarthritis. From what I hear, this may apply to you (regarding the person who asked the question). However, there many other causes of these nonspecific symptoms.
• The disease can affect any organ in subtle and profound ways. Therefore, many of the symptoms can be overlooked or lead to misdiagnosis for years before sarcoidosis is discovered as the cause.

How do you diagnose sarcoidosis?

• Because many of the symptoms of sarcoidosis are nonspecific, diagnosis is not always straightforward. The diagnosis is generally via a combination of clinical, radiographic and histological findings.
• No blood findings are specific for sarcoidosis. However, the angiotensin-converting enzyme is elevated in 2/3 of patients. 5% of positive angiotensin-converting enzyme tests are false-positives for sarcoidosis.
• Chest x-ray and Chest CT can show typical findings, but similar findings can also be seen with other diseases.
• Gallium 67 nuclear medicine lung scan can show characteristic findings but it is also not perfect.
• Biopsy and bronchial lavage is sometimes used to help diagnose.

Prognosis?

• Sarcoidosis can be acute, subacute, self limiting (goes away on its own) or be chronic.
• Most people who present with acute disease are left with no lasting problems.
• A little less than ½ are left with permanent damage, but most of the time those lasting problems are minor.
• 15-20% of cases remain active or recur intermittently.  

Treatment?

• Since the disease goes away on its own in about 50% of patients, the question is when to treat, if at all. Treatment is usually reserved for severe cases.
• Therapies include immunosuppressants such as glucocorticoids (prednisone) for 4-6 weeks with a slow 2-3 month taper.
• Steroids are not without significant side effects and the decision to treat should be thought through carefully.