Identifying the Lowest Effective Initial Dose of Prednisolone for the Treatment of Subacute Granulomatous Thyroiditis: A Systematic Review and Meta-Analysis.

Background: Subacute granulomatous thyroiditis (SAGT) is an inflammatory disease due to viral infections. Glucocorticoids, especially prednisolone (PSL), are one of the first approaches in the treatment of patients with SAGT. To date, no study has determined the lowest effective dose of prednisolone with the lowest recurrence rate in the treatment of SAGT. This study aimed to use meta-analysis methods to identify the appropriate dosage of prednisolone with the lowest recurrence rate in the treatment of patients with SAGT.

Methods: This study was conducted according to the PRISMA checklist in February 2021. Two independent researchers performed a search for relevant literature published before March 2021 in English databases, including Scopus, MEDLINE (via PubMed), Web of Science, Cochrane Library, Google Scholar, EMBASE, and also Persian electronic databases including SID, Iran medex, Magiran, and Irandoc. The search algorithm was initially developed by using a combination of MeSH terms, keywords, and also Boolean operators ("AND"; "OR"; "NOT"): Subacute thyroiditis, De Quervain Thyroiditis, Glucocorticoids, Prednisolone, Recurrence, and Meta-Analysis. All statistical analyses were performed using STATA 15.0 (StataCorp LLC, College Station, TX, USA) and SPSS 17.0. A random-effects model based on Metaprop was applied for the Meta-analysis. To assess heterogeneity between studies, the chi-squared test and I2 index were used, and for evaluating publication bias, funnel plots and Egger tests were performed.

Results: The overall recurrence rate was 14.72% [95% CI: 9.63- 20.58] and there was a significant heterogeneity among the studies [I2 = 69.56%; P=0.000]. To evaluate the lowest effective dose of prednisolone, we divided the studies into two groups based on the mean initial dose of prednisolone: less than or equal to 20 mg/day (group one) and greater than 20 mg/day (group two). The recurrence rate in group 1 was 11% [95% CI: 5.7- 16.2] and in group 2 was 23.6% [95% CI: 11.5- 35.6]. Significant correlations were observed between the initial mean dose of PSL and recurrence rate (r= 0.71; P= 0.013). Begg's funnel plot had no evidence of publication bias in these studies (p=0.160).

Conclusion: According to the results of this meta-analysis, 15 to 20 mg/day of prednisolone is the most effective dosage with the lowest recurrence rate in the treatment of subacute Granulomatous thyroiditis.