No single test can confirm that a person has lupusbut a doctor may use several types of blood tests to reach a lupus diagnosis. These include tests to look for antinuclear antibodies (ANA) in the blood.
Systemic lupus erythematosus (SLE)or lupusis a chronic autoimmune disease resulting from the immune system attacking the body’s own tissues. As lupus symptoms often overlap with other autoimmune diseasesinfectionsor illnessesa doctor must rule them out first.
This process may involve several blood tests to detect inflammationantibodiesand red and white blood counts.
This article discusses each blood test for lupus and its usesincluding what a positive result is and what it means.
< data-emotion="css-global 114pms8">@media tablet{h2.with-image-at-left{float:right;}h2.with-image-at-right{float:left;}h2.with-image-at-left,h2.with-image-at-right{width:calc(100% - 280px);}}Share on PinterestLourdes Balduque/Getty Images
Blood tests play a vital role in helping doctors to diagnose and manage lupus. These tests detect changes in specific components of blood or detect antibodies. Antibodies are proteins that the immune system makes to protect the body.
Doctors may order tests to detect the following in the blood:
A person with ANA antibodies in their blood can have an autoimmune conditionsuch as lupus. Unlike other antibodies — that instruct immune cells to attack foreign cells in the body — ANAs tell the immune cells to attack the nuclei of the body’s own cells.
This test is usually one of the first tests a doctor orders if they suspect lupus. Around 97 in 100 people who have SLE receive a positive result.
Evaluation
A positive result means a high number of ANAs is present in the blood. The test reports these results as a titer (ratio)indicating the amount of ANAs in the blood. While a titer of 1:640 can suggest a person has an autoimmune conditiona doctor will assess the results further.
A positive result does not necessarily mean a person has lupusbut a negative result may indicate that lupus is less likely.
When ANA results are positivea doctor orders more tests to look for specific antibodiesincluding:
Anti-double-stranded deoxyribonucleic acid (Anti-dsDNA): This refers to antibodies against the genetic material of the cell. Presenting with anti-dsDNA usually indicates lupus.
Anti-Sm: This may occur in people with lupus.
Anti-U1 ribonucleoprotein (RNP): This antibody occurs in autoimmune diseasesincluding lupus.
Anti-Ro/SSA and anti-La/SSB: If these antibodies are presentit can indicate that someone is having lupus complications.
Antiphospholipid antibodies: About a third of people with lupus test positive for these.
A CBC shows how much of these components is in the blood. It also looks for the amount of hemoglobina protein that is present in red blood cells. CBC is a routine blood test.
When blood components are not within the typical rangesuch as having a low WBC count and low hemoglobinit can indicate something is wrong.
There are several results from a CBC that potentially indicate lupus:
Low hemoglobin: This sometimes indicates anemiaa common condition for people with lupus. Results less than 13.5 grams per deciliter (g/dL) in males or less than 12 g/dL in females can indicate anemia.
Low white blood cell count (leukopenia): Lupus can cause a person to have a low WBC count due to antibodies that destroy these cells. Figures may vary between labsbut a WBC count below 4,000 cells per microliter of blood is typically considered low.
The ESR generally shows how quickly RBCs separate from other blood components and settle at the bottom of a test tube. Other names for it are sedimentation rateor “sed rate.”
If the test shows a high ESRit indicates inflammation in the bodypossibly due to lupus. This is likely because inflammation causes the RBCs to clump together faster. Typical ranges for ESR are as follows:
less than or equal to 20 millimeters per hour (mm/hr) for females 50 years old and younger
less than or equal to 15 mm/hr for males 50 years old and younger
less than or equal to 10 mm/hr for a child
A faster sed rate does not mean a person has lupus. It can be high for other reasonssuch as:
infection
arthritis
certain cancers
heart disease
other autoimmune diseases
Howeveralongside other test resultsthis can be a good indicator of lupus.
Doctors may use this test to detect inflammation. The liver produces CRP during an inflammatory processmeaning a higher amount is likely because inflammation is present in the body.
High levels of CRP proteins are common for people with lupus.
According to a 2023 articlea moderate elevation of 1–10 mg/dL may indicate systemic inflammation. Results from other tests are necessary to determine if the elevation is due to lupus.
A doctor will order various tests to diagnose a person with lupus. Howevernone of these tests alone can give a definitive positive indication of the condition.
Blood tests with other tests — such as urine tests and imaging — are necessary to gather information that may lead to a lupus diagnosis. Generallyblood tests that detect ANAelevations in ESR and CRPlow WBCsand low hemoglobin can help the diagnostic process.
Medical News Today has strict sourcing guidelines and relies on peer-reviewed studiesacademic research institutionsand medical journals and associations. We only use qualitycredible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
