Antiphospholipid syndrome and kidney damage: diagnosis

Laboratory Diagnosis of Antiphospholipid Syndrome

Characteristic signs of antiphospholipid syndrome are thrombocytopenia, usually moderate (the number of platelets is 100 000-50 000 in 1 μl) and not accompanied by hemorrhagic complications, and Coombs-positive hemolytic anemia. In a number of cases, a combination of thrombocytopenia with hemolytic anemia (Evans syndrome) is noted. In patients with nephropathy associated with antiphospholipid syndrome, especially with catastrophic antiphospholipid syndrome, Coombs-negative hemolytic anemia (microangiopathic) may develop. In patients with the presence of lupus anticoagulant in the blood, lengthening of activated partial thromboplastin time and prothrombin time is possible.

Immunological markers of antiphospholipid syndrome are antibodies to cardiolipin of classes IgG and / or IgM, AT to beta ₂ GP-I, coagulologic marker - lupus anticoagulant. The diagnosis of antiphospholipid syndrome is established with a double or more (with an interval of not less than 6 weeks) detection of antibodies to cardiolipin in medium or high titers and / or lupus anticoagulant, determined by the lengthening of clotting time in phospholipid-dependent coagulation tests. Immunological and coagulologic diagnostics of antiphospholipid syndrome are not interchangeable, but complement each other, as antibodies to cardiolipin are more sensitive, and lupus anticoagulant is more specific. Only the use of both types of studies makes it possible to verify the diagnosis, since the use of only one method leads to diagnostic errors in almost 30% of cases.

Instrumental diagnosis of antiphospholipid syndrome

• When patients with a verified diagnosis show signs of kidney damage, a morphological confirmation of the thrombotic process in the kidney vessels is necessary, and therefore a kidney biopsy is indicated.
• An indirect method of diagnosing nephropathy associated with an antiphospholipid syndrome is ultrasound of kidney vessels, with which it is possible to detect ischemia of kidney parenchyma in the form of impoverishment of the intrarenal blood flow (in the color Doppler mapping mode) and decrease in its speed, especially in the arc and interlobar arteries.

Direct evidence of thrombosis of the intracranial vessels is the infarction of the kidney, which when UZDG has the appearance of a wedge-shaped section of increased echogenicity deforming the external contour of the kidney.

Differential diagnosis of antiphospholipid syndrome

Differential diagnosis of antiphospholipid syndrome and kidney damage is primarily carried out with "classical" forms of thrombotic microangiopathy, HUS and TTP, as well as with kidney damage in systemic diseases, especially in systemic lupus erythematosus and systemic scleroderma. The catastrophic antiphospholipid syndrome should be differentiated from rapidly progressive lupus nephritis and acute scleroderma nephropathy. It is advisable to include nephropathy associated with antiphospholipid syndrome in the range of diagnostic search for acute renal failure, acute hypertension and hypertension, especially severe or malignant, that has developed in young patients and is accompanied by impaired renal function.

[1], [2], [3], [4], [5], [6], [7]