The diagnostic value of blood cell-derived indexes in subacute thyroiditis patients with thyrotoxicosis: a retrospective study.

Background: Both subacute thyroiditis (SAT) and Graves' disease (GD) can lead to thyrotoxicosis, but the methods to distinguish these two diseases are relatively complex. Therefore, it is necessary to find biomarkers which can quickly and efficiently identify the two kinds of thyrotoxicosis. Blood cell-derived indexes are widely used to evaluate systemic inflammation. We aimed to evaluate the diagnostic value of blood cell-derived indexes in SAT patients with thyrotoxicosis. Methods: Totally 139 SAT patients with thyrotoxicosis, 146 GD patients, and 100 euthyroid individuals were enrolled in the study. Complete blood cell (CBC) count, thyroid function, neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), systemic immune-inflammatory index (SII), systemic inflammation response index (SIRI), aggregate inflammation systemic index (AISI), and mean platelet volume to platelet ratio (MPR) were evaluated in all subjects. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the capacity of blood cell-derived indexes in differentiating SAT patients with thyrotoxicosis from GD patients. We also evaluated the association between blood cell-derived indexes and other laboratory indicators and clinical outcomes in SAT patients. Results: NLR, PLR, MLR, SII, SIRI, and AISI were significantly higher in the SAT group. MPR was significantly lower in the SAT group. A formula including NLR, PLR, MLR, SII, SIRI, AISI and MPR was developed. The combination formula with an optimal cutoff of 0.426 showed the better diagnostic value [area under the curve (AUC) =0.921; 95% confidence interval (CI): 0.891-0.950; P<0.001; sensitivity, 87.1%; specificity, 83.6%]. However, thyroid function, erythrocyte sedimentation rate (ESR), thyroid peroxidase antibodies (TPOAb), and blood cell-derived indexes, were not found to be significantly associated with hypothyroidism and recurrence. Conclusions: We developed a formula combining 7 blood cell-derived indexes. The combination formula could be a novel biomarker to distinguish SAT patients with thyrotoxicosis from GD patients. However, we did not find significant association between the blood cell-derived indexes and clinical outcomes in SAT patients.