Endocrine Abstracts

JOINT1840

Background: Subacute thyroiditis (SAT) and Graves’ disease (GD) are characterized by thyrotoxicosis with different treatment approaches. It may not always be easy to distinguish these two diseases. We aimed to evaluate the utility of blood cell derived parameters in the differential diagnosis of SAT and GD. Additionally, we investigated the factors affecting the development of recurrence and permanent hypothyroidism in the patients with SAT.

Methods: 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.

Results: 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 cells percentage (LUC%) and the ratios of eosinophil/monocyte (EMR), eosinophil/lymphocyte (ELR), eosinophil/neutrophil (ENR), eosinophil/platelet (EPR), MPV/neutrophil, MPV/monocyte and MPV/platelets were significantly lower in the SAT group. Among these markers, SII with an optimal cutoff of 652,784 showed the best diagnostic value [area under the curve (AUC) = 0.875; 95% confidence interval (CI): 0,85-0,90; P < 0.001; sensitivity, 81%; specificity, 80%]. No significant association was observed between these parameters and recurrence or permanent hypothyroidism. Recurrence occurred in 8% and permanent hypothyroidism developed in 26% of the patients with SAT. Recurrence was not observed in the group receiving NSAIDs or in those who remained untreated, whereas 15% of patients treated with methylprednisolone (MPS) experienced recurrence (P < 0.001). When comparing patients with and without recurrence in MPS group, pre-treatment TSH were significantly higher in the recurrence group, while fT3 and fT4 were significantly lower (p: 0.04, 0.048 and 0.03 respectively). In the univariate logistic regression analysis, we found that low fT4 levels in the MPS group increased the risk of recurrence (Hazard ratio: 0.46, 95% CI=0.23-0.93, P = 0.032).

Conclusion: 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/neutrophil, and MPV/monocyte ratios and revealed that they are significantly different between these two diseases.