Doctors use a variety of diagnostic tests and procedures to rule out lupus, a chronic autoimmune disease that can affect any part of the body. Lupus is difficult to diagnose because its signs and symptoms often mimic those of other diseases. There is no single test that can definitively diagnose lupus, so doctors must rule out other possibilities before confirming a lupus diagnosis. The diagnostic process involves a thorough review of the patient’s medical history, a physical exam, and specific laboratory and imaging tests. This article provides an overview of how doctors methodically rule out lupus and other conditions to arrive at a correct diagnosis.
Medical History
The first step doctors take in ruling out lupus is to conduct a medical history. They will ask detailed questions about current and past symptoms, including onset, duration, location, severity, aggravating and relieving factors, and effects on daily living. Doctors specifically look for signs and symptoms commonly associated with lupus, such as:
– Fatigue
– Fever
– Joint pain or swelling
– Muscle pain or weakness
– Rash, particularly on the cheeks and bridge of the nose
– Chest pain when taking a deep breath
– Mouth or nose sores
– Hair loss
– Sensitivity to sunlight
– Swelling in the legs or around the eyes
– Fingers turning white or blue when cold or under stress (Raynaud’s phenomenon)
The medical history provides clues about what signs and symptoms the patient is experiencing that may point to lupus. However, lupus symptoms can come and go over time and often resemble those of other diseases. A thorough review of medical history allows doctors to identify any clinical features that may be indicative of lupus, but additional testing is needed to rule it in or out.
Physical Exam
After taking the medical history, doctors will conduct a complete physical exam. This allows them to look for specific signs of autoimmune activity that may be associated with lupus. The exam typically involves:
– Checking temperature, blood pressure, pulse and respiration rate
– Examining the skin for rashes or lesions
– Looking in the mouth and nose for sores, swelling, or discoloration
– Feeling and applying pressure to the joints to check for pain, swelling, and limited range of motion
– Examining fingers and toes for discoloration or ulcers
– Listening to heart and lungs for abnormalities
– Feeling the abdomen for fluid accumulation or enlargement of organs
– Evaluating reflexes and muscle strength
– Assessing mental status and mood
Abnormal findings during the physical exam, such as joint inflammation, skin rashes, oral ulcers, fever, hair loss, or lung crackles can provide evidence to support a lupus diagnosis. However, many of these signs can also be indicative of other conditions. The physical exam gives doctors important clinical data, but cannot definitively rule in or out lupus.
Laboratory Tests
While medical history and physical exam provide valuable information, doctors rely heavily on laboratory testing to rule out lupus. Some of the main laboratory tests include:
Complete blood count (CBC) – This checks for low red blood cell, white blood cell, and platelet counts which can indicate autoimmune activity and systemic inflammation.
Erythrocyte sedimentation rate (ESR) – This detects inflammation by measuring the rate at which red blood cells settle to the bottom of a test tube. A faster than normal settling rate indicates elevated inflammation.
C-reactive protein (CRP) – This protein increases when there is inflammation in the body. High CRP indicates an inflammatory or autoimmune response.
Antinuclear antibody (ANA) test – This is the primary lab test for lupus. A positive ANA indicates an overactive immune system and the possible presence of an autoimmune disease. However, a positive ANA does not definitively confirm lupus, as many healthy individuals may have a positive ANA.
Anti-dsDNA antibody – This is one of the most specific antibody tests for lupus. A positive anti-dsDNA indicates the immune system is producing antibodies that attack the body’s own cells and is strongly associated with lupus.
Anti-Sm antibody – This antibody is only present in 5-30% of lupus patients, but is highly specific for systemic lupus erythematosus. A positive Anti-Sm indicates autoimmunity specific to lupus.
Antiphospholipid antibodies – These autoantibodies increase the risk of blood clots. High levels can indicate the presence of lupus anticoagulant and antiphospholipid antibody syndrome, which frequently occur alongside lupus.
Complement levels (C3, C4, CH50) – Low complement protein levels indicate autoimmune activity and inflammation. Lupus patients often have low complement.
Complete urinalysis – The presence of excessive protein, red blood cells, or cellular casts in the urine may indicate lupus kidney involvement.
While some of these blood and urine tests can strongly support a lupus diagnosis, doctors must interpret the results in the context of the full clinical picture. No single lab test can definitively diagnose lupus. Doctors use lab results to rule out other potential causes and determine the likelihood that symptoms are explained by lupus.
Imaging Tests
In addition to lab testing, doctors may use imaging techniques to rule out other diseases and identify any abnormalities suggestive of lupus:
X-rays – Helpful for detecting lung inflammation such as pleurisy, chronic bone tissue loss, arthritis, and avascular necrosis.
Echocardiogram – Uses ultrasound waves to produce images of the heart. This allows doctors to identify pericarditis, valvular abnormalities, and other signs of cardiovascular involvement that can occur with lupus.
MRI – Provides detailed 3D images of organs and tissues. Can detect neurologic, kidney, and musculoskeletal system involvement in lupus patients.
CT scan – Uses x-rays and computer modeling to create cross-sectional images of organs and structures. May identify lung disease, enlarged lymph nodes, and kidney or spleen abnormalities.
Medical imaging provides visualization of the body’s structures and organs. It can help identify organ system involvement that often accompanies lupus. Imaging does not confirm lupus, but aids doctors in ruling out other potential causes of symptoms.
Additional Testing
Sometimes specialized tests are needed to rule out specific conditions that can mimic lupus:
Thyroid tests – Hypothyroidism and hyperthyroidism cause fatigue, weight changes, and hair loss that may resemble lupus. Thyroid testing helps ensure the thyroid is functioning normally.
Rheumatoid factor – This antibody is present in 70-80% of rheumatoid arthritis patients, but less than 25% of lupus patients. Testing helps differentiate between these two autoimmune diseases.
Lyme disease tests – Lyme can cause symptoms like fatigue, joint pain, and neurologic issues that may suggest lupus. Lyme testing like ELISA and Western Blot are used to rule it out.
Mononucleosis testing – Acute mono can mimic early lupus with fatigue, swollen glands, and fever. Monospot testing for heterophile antibodies helps exclude mono.
Skin biopsy – Observing skin samples under a microscope can help diagnose discoid lupus rashes and distinguish them from other skin conditions.
These are just a few examples of specific tests doctors may use to exclude other diseases with signs and symptoms resembling lupus. The diagnostic process requires meticulous testing to systematically rule out all other possibilities.
Putting the Pieces Together
After completing the medical history, physical exam, laboratory testing, and any additional necessary procedures, doctors analyze all the data. No single finding confirms lupus. Doctors must interpret the entire constellation of clinical signs, symptoms, and test results. They rule out lupus if an alternative diagnosis fully explains the clinical picture. However, if the patient’s manifestations cannot be attributed entirely to another disease, the evidence may be sufficient for a lupus diagnosis.
Doctors may classify lupus as:
Systemic lupus erythematosus – Broader disease activity involving multiple organs and systems
Discoid lupus – Skin condition limited to rashes and scarring on the face, scalp, ears, chest, and arms
Drug-induced lupus – Caused by certain prescription medications
Neonatal lupus – Rare condition acquired from antibodies transferred in utero from a mother with lupus
Ruling out lupus is challenging due to the disease’s variable presentations and overlap with other conditions. Doctors must undertake a rigorous diagnostic process by gathering data from multiple sources, excluding alternative diagnoses, and collaborating across specialties to reach the most likely explanation for the patient’s clinical presentation. While complex, this systematic approach helps ensure lupus is accurately and efficiently ruled in or out.
Key Takeaways
– There is no single definitive test for lupus, so ruling it out requires a combination of medical history, physical exam, lab work, and imaging tests.
– Doctors interpret results in the context of the patient’s full clinical picture to determine if lupus is the most likely explanation for symptoms.
– Ruling out lupus involves excluding other diseases like rheumatoid arthritis, thyroid disorders, lyme disease, and blood disorders that can mimic lupus.
– Classification of systemic, discoid, drug-induced, or neonatal lupus requires isolating the type of disease activity.
– While complex, methodically ruling out lupus by differential diagnosis helps avoid misdiagnosis and ensures patients get accurate and timely treatment.
The Bottom Line
Ruling out lupus is a challenging, multifaceted diagnostic process. Doctors carefully gather clinical information through medical history, physical examination, laboratory testing, and medical imaging. They analyze results in a holistic manner to exclude alternative diagnoses and discern whether lupus is the most likely explanation for the patient’s signs, symptoms, and examination findings. This systematic approach provides the best possibility of accurately ruling out lupus so appropriate treatment can begin.
