The Role of Blood Cell-Derived Parameters in the Differential Diagnosis of Subacute Thyroiditis and Graves' Disease and Long-Term Outcomes in Subacute Thyroiditis.

To assess the utility of blood cell-derived parameters in differentiating subacute thyroiditis (SAT) from Graves' disease (GD) and their association with recurrence and the development of permanent hypothyroidism in the patients with SAT. The study involved 414 patients with SAT, 415 patients with GD, and 92 healthy controls. Pre-treatment hematological parameters were retrospectively compared, especially in cases where differentiation is challenging, including painless SAT, acute phase reactants negative SAT, and TSI, TRAB (Thyroid Stimulating Immunoglobulin, TSH-receptor-antibodies) negative GD. Factors influencing recurrence and permanent hypothyroidism were also analyzed in SAT group. When compared with the GD group, ratios of neutrophil/lymphocyte (NLR), platelet/lymphocyte (PLR), systemic inflammatory response index (SIRI), systemic immune inflammatory index (SII) and pan immune inflammation value (PIV) were significantly higher, while large unstained cell percentage (LUC%) and the ratios of eosinophil/monocyte (EMR), eosinophil/lymphocyte (ELR), eosinophil/neutrophil (ENR), eosinophil/platelet (EPR), mean platelet volume/neutrophil (MPV/NEU), MPV/monocyte and MPV/platelets were significantly lower in the SAT group. SII demonstrated the highest diagnostic value, with an optimal cutoff of 652,784. No significant association was observed between these parameters and recurrence or permanent hypothyroidism. Differentiation between SAT and GD can be reliably achieved using blood cell-derived parameters, and that these markers are also applicable in groups where differentiation is challenging. To the best of our knowledge, this is the first study to investigate the LUC%, ELR, ENR, EPR, MPV/NEU, and MPV/monocyte ratios and revealed that they are significantly different between these two diseases.