Haematological Indices in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a clinically common autoimmune disease characterized by abnormal immune response to autologous tissue, eventually resulting in systemic disorders and diverse clinical manifestations of the patients.

The pathogenesis of SLE remains unclear, but environmental triggers and genetic factors contribute to the destruction of immune tolerance systems, the production of immunological lymphocytes, antibodies, and inflammatory cytokines.

The clinical manifestations of SLE range from constitutional symptoms, such as fever, sweats, weight loss, joint pain and skin rashes (including the classic butter fly rash), to more serious features, including the involvement of the central nervous system and kidneys.

However, to make a clinical diagnosis of SLE, The SLICC criteria require either that a patient satisfy at least 4 of 17 criteria, including at least 1 of the 11 clinical criteria and one of the six immunologic criteria, or that the patient has biopsy-proven nephritis compatible with SLE in the presence of antinuclear antibodies (ANA) or anti-double-stranded DNA (dsDNA) antibodies. Patients with higher disease activity often present severer damage of tissues and organs.

SLE is characterized by high heterogeneity, a complex pathophysiology and various clinical manifestations; thus, no test alone is sufficiently sensitive or specific for diagnosis. Active and inactive SLE patients were evaluated according to SLE disease activity index (SLEDAI).There is significant interest in the identification of biomarkers that can predict SLE and quantify disease activity.

Neutrophils and lymphocytes play major roles in inflammatory processes. Under inflammatory conditions, neutrophil and lymphocyte counts undergo temporary changes. Neutrophil to lymphocyte ratio (NLR) is calculated as the absolute count of neutrophils divided by the absolute count of lymphocytes.

As an index of systemic inflammation, NLR has been identified to be a useful index for the differential diagnosis or prognostic prediction of diseases. NLR can be calculated easily and less costly as compared with detection of other inflammatory cytokines that could be used as biomarkers for inflammatory response or disease activity in SLE patient.

The platelet-to-lymphocyte ratio (PLR), red blood cell distribution width (RDW), and similar parameters [ eg, neutrophil-to-lymphocyte ratio (NLR) and mean platelet volume (MPV) ], which can be easily obtained using peripheral blood parameters, have been regarded as novel, accurate inflammatory biomarkers in many diseases.

MPV is a biomarker of platelet turnover, whereas platelet activation is a marker of inflammation. Previous studies have reported that MPV is correlated with the inflammatory process and disease activity in RA and ankylosing spondylitis, but the relationship between MPV and SLE remains controversial.

Complement system activation, production and partial deposition of complement fragments, and subsequent inflammation all play critical roles in the pathogenesis of SLE. During the complement activation pathway, Complement 3 was at the core position.