Complete Blood Count Test in Rheumatology: Not Just a Screening Test

Rheumatic disorders are chronic and common diseases, which especially involve connective tissue and may be associated with the damage to vital organs such as heart and kidney. Diagnosis, prognosis, determining the probability of severe complications, monitoring and evaluation of the response to treatment in such patients require specialized, expensive and time-consuming laboratory tests.In this review article, we assessed the value of parameters of routine, inexpensive, and available Complete Blood Count (CBC) in detecting disease activity and explaining the prognosis of a number of rheumatic disorders, including systemic lupus erythematosus and rheumatoid arthritis by reviewing the results of searching Google Scholar search engine and PubMed databases over 2000 - 2021.Review of previous articles showed that while traditional Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) tests do not have sufficient specificity to appraise disease activity, CBC derived inflammatory biomarker Neutrophil-to-Lymphocyte Ratio (NLR) is able to assess disease activity and response to treatment in Rheumatoid Arthritis (RA). Also, Mean Platelet Volume (MPV) and NLR can determine the prognosis of renal involvement in Systemic lupus erythematosus (SLE).Although CBC-based parameters are not completely specific and sensitive to rheumatic disorders, but based on the results of previous studies, these parameters, particularly red cell distribution width (RDW), MPV, NLR and platelet to lymphocyte ratio (PLR) are inflammatory biomarkers with a prognostic role in rheumatic disorders that can also assess activity of the disease.