The diagnosis of lupus depends a lot on the manifestations that reveal the disease. The purpose of the necessary examinations is, on the one hand, to discard the possibility of a disease that would resemble lupus and, on the other hand, to affirm the diagnosis if possible. The most useful tests for the diagnosis of lupus are:

"Routine" biological examinations

< The search for a decrease in blood cells in the bloodstream (cytopenia): anaemia (hemolytic or inflammatory, decrease in red blood cells), lymphopenia, neutropenia (decrease in white blood cells, lymphocytes or neutrophils), autoimmune thrombocytopenia (decrease in platelets) .

< The search for kidney damage by analysing the renal function (measured by blood creatinine) and urine, which makes it possible to know if there is an abnormality of the renal filter. If this filter is damaged, the urine will contain proteins (including albumin), but also red blood cells (hematuria) or white blood cells (leukocyturia). These renal abnormalities are not specific to lupus, but are essential to look for when talking about this disease. They can be detected by a simple analysis of the urine strip.

< Hepatic biology analysis (transaminases, alkaline phosphatases) is especially useful for eliminating another disease (virus).

Immunological examinations

< It is first of all the search for a high level of immunoglobulins (hypergammaglobulinemia), which reflects the activation of the immune system

< The most important biological examinations to confirm the diagnosis are immunological with the global identification of antinuclear antibodies and their components (anti-native DNA, anti-Ro/SS-A and anti-La/SS-B, anti-Sm, anti-RNP ...) and possibly the search for an activation of the complement system proteins resulting in a decrease of these proteins in the blood (called hypocomplementemia) .

These immunological examinations must systematically include the search for antiphospholipid antibodies.  These are autoantibodies that can "thicken" the blood, and lead to a risk of clotting (thrombosis) in the veins (called phlebitis) or in the arteries.

Several other examinations can be useful depending on the signs that the patient presents

< A skin biopsy may be necessary to confirm, through histological analysis, the diagnosis of lupus when confronted with a lupus-like skin lesion. But this is useful only when the diagnosis is hesitant.

< In case of suspicion of cardiac or vascular damage (vein or artery), it is necessary to perform an ultrasound - Cardiac Doppler

< In case of kidney damage, a kidney biopsy should be discussed to find out how severe the damage is.

< In case of neurological damage, it is necessary to explore the brain by examinations such as an MRI and / or analyse, by a lumbar puncture, the fluid that circulates around the brain (called the cerebrospinal fluid)

< A significant decrease in blood cells (cytopenia) may warrant a study of the hematopoietic bone marrow (which produces blood) that is taken under local anesthesia (myelogram).

< X-rays or another imaging technique (MRI, ultrasound) are sometimes necessary in case of joint and/or bone pain, to rule out another disease.

The list of necessary examinations in lupus cannot be exhaustive, since it depends on the expression of the disease in each patient at a given time in life. All these examinations may be necessary to make the diagnosis of lupus, but also, and above all, to define the type and extent of the damage to each organ and to monitor the evolution of the disease to treat relapses as soon as possible. This assessment is essential to choose the right treatment.