investigations

Last reviewed 08/2021

  • serology
    • autoantibodies
      • antinuclear antibodies (ANA) - seen in 98% of patients
        • the specificity is low since ANAs are found in many other conditions such as scleroderma, polymyositis, dermatomyositis, rheumatoid arthritis
      • anti-double-stranded DNA (dsDNA) - highly specific for SLE, only present in around 70% of patients
      • other autoantibodies include - anti-Smith, anti-ribosomal P and anti-proliferating cell nuclear antigen (PCNA) (1)
    • lupus anti-coagulant
  • FBC
    • normochromic normocytic anaemia
    • haemolytic anaemia (in less than 15% - note that positive Coomb's test occurs in 65% of cases)
    • leucopaenia - especially lymphocytopaenia
    • thrombocytopaenia
  • polyclonal hypergammaglobulinaemia
  • ESR
    • usually raised
    • not always reliable but changes may correlate well with disease activity
  • CRP
    • usually do not increase unless there is arthritis or serositis
    • consider infection if increased (1)
  • reduced serum complement concentrations -
    • usually, firstly of C4, then C3, C1q and total haemolytic complement activity (CH50)
    • thought to result from complement consumption by immune complexes

Tests may be performed for specific clinical manifestations for example, renal function tests; tissue biopsy of skin, kidney, lymph nodes; examination of synovial fluid.

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