Sarcoidosis is a disease in which the immune system mistakenly attacks the body’s own cells and tissues. It is characterized by the presence of immune cell clusters, called granulomas, forming in various organs and tissues.
This disease can be of limited duration and go away on its own, or be chronic with a likelihood of long-term disability. In its chronic form, granulomas build in organs causing a range of symptoms of varying intensity. Because sarcoidosis shares symptoms with other diseases, it can be difficult to correctly and quickly diagnose.
Blood and urine tests are low-risk and minimally invasive ways of evaluating what is happening inside a person. They can help medical professionals determine the potential existence of disease, estimate degree of organ involvement, and show if inflammation is present. With difficult-to-diagnose diseases like sarcoidosis, such tests can help professionals narrow down the conditions likely to cause reported symptoms.
Blood tests involve a medical professional taking a small sample of blood from a vein on the arm or a finger prick. Because of the location and the small amount of blood taken, this procedure is very low risk.
The blood is then analyzed in a laboratory for the presence of different chemicals and enzymes, as well as the ratios of iron, water, and different nutrients.
The normal ranges of these chemicals and enzymes in blood are well-known, and when certain ones fall outside of these ranges that could be a single of diseases, usually in earlier stages.
However, blood tests are very sensitive to the person’s activities just before a test. This means that if the person eats, exercises, or drinks a lot of water prior to taking a blood test, the ratios of the chemicals can become skewed. For this reason, a person may be asked to fast for eight to 12 hours before giving a blood sample and samples are often requested in early morning, so their blood chemistry will be affected by diet or exercise. In some cases, a person may also be asked not to drink water prior to the test.
Urine tests or urinalysis are similar, but generally do not require any fasting or other lifestyle changes, although people should inform their doctor of medications or vitamin supplements being taken, as these can affect a urinalysis.
A person generally collects the sample, passing urine into a cup for testing. Medical professionals can also collect the urine if a patient is unable to do so, typically by inserting a thin, flexible tube called a catheter through the urinary tract opening and into the bladder.
A urine sample is assessed in a laboratory for its concentration, color, and content, like the presence of blood cells, calcium levels, and protein types and levels.
Although urine tests have advantages such as requiring little preparation, they are not overly sensitive. They mainly reveal conditions in which the liver, kidneys, or bladder are affected.
Usefulness of blood and urine tests
Blood tests are able to also detect levels of inflammatory cells such as angiotensin-converting enzyme (ACE) and immune cells called T-cells. High levels of these cells indicate an inflammatory condition, such as sarcoidosis.
Blood tests can also reveal other chemistry abnormalities that indicate problems in organs, possibly distinguishing which organs affected by sarcoidosis.
Although not definitive, the ease of blood and urine tests make them a useful first step in diagnosing sarcoidosis and in ruling out other conditions.
Limits to these tests
Although blood and urine tests can help determine the presence of sarcoidosis or similar conditions, neither is sensitive enough to distinguish sarcoidosis from other conditions.
High calcium levels, for example, could also indicate diseases affecting the bones, thyroid, and kidneys. They can also be a symptom of too much vitamin D or calcium intake, or of certain cancers.
Likewise, excessive inflammatory cells in the blood and inflammatory markers in the urine can be markers of a number of inflammatory conditions.
Still, blood and urine tests can be valuable initial steps leading to a determination of whether sarcoidosis is present.
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