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Diagnosis and Tests

Understanding Lupus Lab Tests & Results

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Lupus lab tests provide objective assessments of the goings on within the body. But, reading your lab test results can be confusing.

Laboratory tests are an essential part of healthcare. They offer insight into changes within the body that can be measured using biological features. In the old days, a clinician may have only told you the interpretation of the result. But, it’s more common now to receive the result values in addition the interpretation.

You can review your lab results in your patient portal or by looking at your after visit report. Electronic medical records standardize the look of lab results, but it’s still possible to find a host of unfamiliar acronyms.

However, specialty labs can create their own reports styles which can make it challenging to find the information you are looking for. They may or may not include an interpretation of the results, and each lab might go about these interpretations differently.

CLIA lab report requirements

Despite this variation, there is hope for standardization. Federal legislation (in the US) known as CLIA requires these reports to contain the same important information. CLIA requires the following information to be on each test result report:

Personal Information

  • Your name and an identification number
    • This identification number ensures that the lab report is really for you. Some labs will use a unique identifying number to maintains your privacy, but the purpose is the same.
  • The address and name of the laboratory
  • The name of the doctor who ordered/authorized the test
  • The date of the test and the date when the report was produced
  • The type (types) of tests performed.

Information on the specimen and test

  • The source of the specimen tested
  • The date and time of the sample collection 
  • Medications or supplements that you are taking which might influence the test results
  • Whether the specimen was damaged or stored improperly
    • Sometimes the test can still be run, but it will change the results
  • The results of the test or tests
    • Typically the lab report will call attention to or highlight:
      • Abnormal results – higher or lower results than what is considered to be the normal range. Not all abnormal results are dangerous or markers of disease, but they are notable
      • Critical results – Abnormal results that are potentially dangerous and require immediate investigation
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What is a Reference Range?

First, abnormal results are determined by a reference range. A reference range is a range of values that represent “normal” variables for humans. The ranges used can vary slightly by laboratory but are relative similar for a given test.  Healthy individuals can have abnormal results, too.

Still, using a range helps to cover normal variation within the body. These ‘normal’ ranges, as defined by that laboratory, are a generally good reference point. When a result falls outside a normal range, this can help direct patients and doctors towards diagnoses, treatments, and/or further testing.

There are also positive and negative results. These happen if the lab test is looking for something specific Positive is the presence of that specific thing, while negative is the absence. An inconclusive test means that the test wasn’t able to determine it for sure, and you and your doctor might have to order another test.

So what lupus lab tests support the diagnosis process?

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Lab Tests for Lupus

Because lupus is a complicated disease, diagnosing lupus requires several blood tests, an assessment of symptoms, and a review of person’s family history.

One of the major tests for lupus is an antinuclear antibody (ANA) test, which looks for antibodies that lock onto targets that are usually found in the nucleus of healthy cells. This causes the immune system to attack these cells, damaging the body instead of protecting it. The immune system attacking healthy cells is the hallmark of autoimmune diseases such as lupus. A positive ANA result (the presence of ANAs) is the first requirement for a diagnosis of lupus. (Around 97% of people with lupus will have a positive ANA.)

Another common lupus lab test is the complete blood count (CBC). This measures the proportions of red blood cells, white blood cells, hemoglobin, and the percentage of red blood cells in the blood (hematocrit).

There are many other tests, both blood-based and urine-based, that look at kidney, liver, and other organ function. You can read more about them here. Overall, with lupus, doctors are looking for evidence of organ damage, inflammation, or antibodies. So, what results tell doctors that this is the case?

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What Do You Need to Really Look for with Lupus?

Specific antibodies and proteins connected to lupus disease activity can be detected in laboratory tests. Common “signals” for lupus include positive results for these lab tests:

  • ANA antibodies
  • Anti-double stranded DNA (anti-dsDNA) antibodies
  • Anti-Sm (Smith) antibody
  • Cardiolipin antibody
  • Lupus anticoagulant protein

Comprehensive metabolic panels (CMPs) can detect problems in the liver, heart, and lungs.

Blood tests can also be used to detect:

 Other blood chemistry levels can also be tied to lupus, as well. Within these tests, there are some specific levels that you should know.

 

ANA Titers and Lupus

ANAs are not simply positive or negative. The ANA result includes a number, known as a titer, which is a measure of the amount of dilution possible in a sample while still being able to measure antinuclear antibodies.

Although the lab report should interpret this for you, a positive ANA result of at least 80 is considered to be typical for SLE. The positive result itself is concerning. A result of 80 means that, even when the blood sample was diluted 80 times, ANAs were detectable. This heavily implies that autoimmune activity is going on. Although some healthy people have positive ANA tests, a high titer supports the identification of symptoms (e.g., pain, fatigue, rashes) are autoimmune disease-related.

Anti-double stranded DNA antibodies (anti-dsDNA) are a particular ANA that is very strongly associated with lupus. Positive tests for anti-dsDNA support a lupus diagnosis.

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C-Reactive Proteins

C-Reactive proteins or CRP are tested with a CRP blood test. Though they are difficult to interpret because everyone’s normal is slightly different, CRP levels are typically low for healthy people. High CRP levels are a sign of inflammation, and variation – ups and downs – can help diagnose flares.

 

White Blood Cell Count

Everyone has white blood cells in the bloodstream. These immune system cells patrol the body and destroy invading pathogens. The typical white blood cell count (for a healthy adult) is between 4000-11,000 WBC per microliter of blood. Children will have more, and the levels can vary between men and women, but this range is a good reference.

White blood cell counts can tell you a lot about what is happening in your immune system. Both too many or too few white blood cells can be caused by inflammation, and low white blood cell counts can indicate infection and certain cancers as well.

 

ESR

According to the Mayo Clinic, results from your sed rate test will be reported in the distance in millimeters (mm) that red blood cells have descended in one hour (hr). The normal range is 0 to 22 mm/hr for men and 0 to 29 mm/hr for women. The upper threshold for a normal sed rate value may vary somewhat from one medical practice to another.

This lab test can be tricky, since it has to be handled delicately. Also, a high ESR doesn’t mean anything on its own, but it can support other findings and other tests and be a path towards diagnosis. A very high ESR is caused by inflammation, anemia, or infection – which can point towards lupus, but also in pregnancy.

So, in general, ESR is something to look at and keep in mind, but it definitely needs to be done with other tests.

 

Creatinine Levels

Creatinine is a substance found in the blood and urine that is produced by muscles as a waste product. The kidneys usually remove creatinine in the blood and transfer it to urine, so that the body can remove it. Abnormal levels of creatinine in the blood can be because of poor kidney function, a symptom of lupus. However, people with lupus should be careful. Creatinine is produced by muscular action, so physical activity can affect the results of the test.

 

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A Lupus Warrior’s Takeaway

Your lab report is going to have a lot of numbers and letters and rangers – but start at these basics and move out from there. Definitely go into your next appointment prepared, with your lab report in one hand and some prepared questions in the other.

Don’t be afraid to review your lupus lab tests or the results. When you have questions ask your lupus treatment team.

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