Background At present, in 30–35% systemic lupus erythematosus (SLE) patients antiphospholipid antibodies (aPL) are associated with the development of secondary antiphospholipid syndrome (APS), including venous and/or arterial thrombosis and other systemic disorders. Practitioners still face certain difficulties in differential diagnosis of the APS positive SLE and are in need for efficient tests to verify the diagnosis. Hp (haptoglobin) is a hemoglobin-binding glycoprotein of α2-globulin serum proteins fraction induced by seromucoids at the early stages of an inflammatory process. There are three phenotypic variants of Hp: Hp 1–1, Hp 2–1 and Hp 2–2. The practical value of Hp test in SLE patients is the possibility to diagnose a genetic predisposition to APS to predict severity of the disease.
Objectives Determine the carriage frequency of different Hp phenotypes in SLE patients with APS, and reveal a correlation between the level of serum Hp and clinical manifestations of APS in SLE patients.
Methods The study is based on the follow-up results of 103 SLE patients under treatment at the Republican Centre of Rheumatology, Tashkent Medical Academy. Entry criteria of patients in the study: reliable diagnosis of SLE, verified in accordance with SLICC (2012) criteria and the informed consent to participation. The secondary APS (SAPS) was based on the Sydney (2006) Classification Criteria for APS. Haptoglobin test was performed using disc polyacrylamide gel electrophoresis (PAGE).
Results We have defined APS in 44 of 103 (42.7%) SLE patients. In 29 of 44 (65%) cases the APS diagnosis was based on major manifestations, and in 15 of 44 (35%) – by the presence of two or more additional signs. Distribution of SLE patients with APS, depending on the Hp phenotype: 38 (86.4%) patients with APS had Hp 1–1, 6 (13.6%) – Hp 2–1, 0 (0%) - Hp 2–2 phenotype (P<0.01, 95% CI). Distribution of SLE patients without APS depending on the Hp phenotype: 23 (39%) patients – Hp 1–1, 27 (45.8%) – Hp 2–1, 9 (15.3%) – Hp 2–2 phenotype. After distribution of the patients into groups by the Hp level, more than 3 g/l (I group) and less than 3 g/l (II group), we have analysed the correlation between Hp and clinical manifestations of APS: thrombocytopenia: I – 7 (22,5%), II – 3 (23,07%), HM – I – 13 (41,9%), II – 4 (30,7%), livedo reticularis: I – 15 (48,3%), II – 5 (38,4%), finger gangrene: I – 5 (16,1%), II – 0 (0%); finger necrosis: I – 6 (19,3%), II – 1 (7,6%); migraine: I – 20 (64,5%), II – 5 (38,4%); chorea: I – 5 (16,1%), II – 2 (15,3%); transitory ischemic attack (TIA): I – 16 (51,6%), II – 7 (53,8%); chronic ulcers of lower extremities: I – 22 (70,9%), II – 8 (61,5%) (P<0.05, 95% CI).
Conclusions Results of our investigation showed that development of SLE and APS is characteristic for Hp 1–1 phenotype, apparently, being a predisposing factor to the autosensitisation and a genetic marker for APS. Furthermore, there is an expressed correlation between Hp level and clinical manifestations of APS.
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Disclosure of Interest None declared
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