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Antiphospholipid syndrome and kidney damage - Diagnosis
Last reviewed: 03.07.2025
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Laboratory diagnostics of antiphospholipid syndrome
Characteristic features of antiphospholipid syndrome are thrombocytopenia, usually moderate (platelet count is 100,000-50,000 in 1 μl) and not accompanied by hemorrhagic complications, and Coombs-positive hemolytic anemia. In some cases, a combination of thrombocytopenia and hemolytic anemia (Evans syndrome) is noted. In patients with nephropathy associated with antiphospholipid syndrome, especially in catastrophic antiphospholipid syndrome, the development of Coombs-negative hemolytic anemia (microangiopathic) is possible. In patients with the presence of lupus anticoagulant in the blood, an increase in activated partial thromboplastin time and prothrombin time is possible.
Immunological markers of antiphospholipid syndrome are antibodies to cardiolipin of IgG and/or IgM classes, AT to beta 2 GP-I, and the coagulological marker is lupus anticoagulant. The diagnosis of antiphospholipid syndrome is established with two or more (with an interval of at least 6 weeks) detection of antibodies to cardiolipin in medium or high titers and/or lupus anticoagulant, determined by prolongation of blood clotting time in phospholipid-dependent coagulation tests. Immunological and coagulological diagnostics of antiphospholipid syndrome are not interchangeable, but complement each other, since antibodies to cardiolipin have greater sensitivity, and lupus anticoagulant has greater specificity. Only the use of both types of research allows the diagnosis to be verified, since the use of only one method leads to diagnostic errors in almost 30% of cases.
Instrumental diagnostics of antiphospholipid syndrome
- When signs of kidney damage appear in patients with a verified diagnosis, morphological confirmation of the thrombotic process in the intrarenal vessels is necessary, in connection with which a kidney biopsy is indicated.
- An indirect method for diagnosing nephropathy associated with antiphospholipid syndrome is ultrasound Doppler imaging of the renal vessels, which can detect ischemia of the renal parenchyma in the form of depletion of intrarenal blood flow (in color Doppler mapping mode) and a decrease in its velocity indicators, especially in the arcuate and interlobar arteries.
Direct confirmation of intrarenal vascular thrombosis is renal infarction, which, when examined by ultrasound, appears as a wedge-shaped area of increased echogenicity, deforming the outer contour of the kidney.
Differential diagnosis of antiphospholipid syndrome
Differential diagnostics of antiphospholipid syndrome and renal damage is carried out primarily with the "classical" forms of thrombotic microangiopathy, HUS and TTP, as well as with renal damage in systemic diseases, especially in systemic lupus erythematosus and systemic scleroderma. 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 in acute renal failure, acute nephritic syndrome and arterial hypertension, especially severe or malignant, developed in young patients and accompanied by impaired renal function.
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