3.1. Literature Search Strategy
A comprehensive and systematic literature search was conducted to identify all relevant studies evaluating minimally invasive thyroid ablation in EBV-associated thyroid disease. Major scientific databases, including PubMed Central, Scopus, Web of Science, SpringerLink, ERIC, and Google Scholar, were searched from their inception through March 2025. To ensure the inclusion of studies from low-resource settings, HINARI was additionally used for full-text access where required. The search strategy adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines (
20) to ensure methodological transparency and reproducibility.
Search terms combined both controlled vocabulary (MeSH terms) and free-text keywords using Boolean operators (AND, OR, NOT) to maximize sensitivity and specificity. The following representative terms were applied across databases: “Epstein-Barr virus and thyroid,” “ultrasound-guided thyroid ablation,” “radiofrequency ablation in autoimmune thyroiditis,” “ethanol ablation and Graves’ disease,” “minimally invasive thyroid interventions,” and “thyroid nodules and viral inflammation.” Reference lists of all included studies were manually screened to identify additional relevant publications not captured in the primary search.
3.2. Inclusion and Exclusion Criteria
Studies were included if they met all of the following criteria: (1) EBV infection confirmed by serological or molecular methods; (2) autoimmune thyroid disease diagnosis, with or without nodular changes; (3) use of minimally invasive thyroid intervention, such as RFA, EA, or MIVAT under ultrasound guidance; and (4) reporting of at least one clinically relevant outcome, thyroid nodule volume reduction, hormonal restoration (TSH, FT3, FT4), recurrence, procedure-related complications, or cosmetic satisfaction
Studies were excluded if they lacked documented EBV status, did not report procedural or endocrine outcomes, were limited to case reports, reviews, or conference abstracts, or scored below 5 on the Newcastle-Ottawa Scale (NOS) for methodological quality.
3.3. Data Extraction Process
Two reviewers independently extracted data using a predesigned standardized form to ensure consistency. Extracted parameters included patient demographics (age, sex, EBV status, and disease type), thyroid hormone levels (TSH, FT3, FT4), nodule characteristics (size, echogenicity, vascularity, and anatomical distribution), and procedural details (type of ablation, energy settings, sedation protocol, duration, and follow-up period). Clinical outcomes—including volume reduction rate (VRR), endocrine stabilization, complication rate (e.g., hypothyroidism, bleeding, infection), recurrence, and hospital stay—were systematically documented. Patient-reported outcomes, when available, such as cosmetic satisfaction and overall quality-of-life improvement, were also extracted. Any discrepancies between reviewers were resolved through discussion, and unresolved conflicts were adjudicated by a third senior reviewer to ensure data accuracy and objectivity.
3.4. Quality Assessment
The ROBINS-I tool was not applied in this review because it is specifically designed for comparative non-randomized studies that evaluate the effect of an intervention relative to a defined control group within a target-trial framework. In the present analysis, most of the included studies were non-comparative observational or procedural reports describing outcomes of image-guided thyroid ablation in EBV-associated thyroid disease, without a concurrent comparator arm. Therefore, several ROBINS-I domains, such as confounding and classification of interventions, were not applicable to our data.
To ensure methodological rigor, study quality was instead appraised using parameters better suited to the nature of the included evidence, focusing on clarity of study design, diagnostic confirmation of EBV infection, transparency and reproducibility of ablation protocols, consistency in reporting clinical and hormonal outcomes, operator experience, and adequacy of follow-up. This context-specific approach, adapted from established observational study appraisal frameworks, provided an accurate and transparent assessment of methodological quality while maintaining alignment with the clinical and procedural scope of the review.
We used the NOS because most included studies were observational cohorts reporting clinical outcomes after image-guided thyroid ablation, making NOS an appropriate, widely accepted tool to appraise nonrandomized evidence. Two reviewers independently applied the NOS across its three domains, Selection, Comparability, and Outcome, with disagreements resolved by a third reviewer to ensure consistency. We predefined decision rules to keep judgments transparent and tailored to our topic: under Selection, studies earned stars for clearly defined cohorts, representative sampling, and, critically for this review, robust EBV ascertainment (serology and/or PCR) as part of exposure/eligibility verification. Under Comparability, stars were awarded when analyses accounted for key confounders relevant to ablation outcomes (e.g., age, baseline thyroid status and autoimmunity, nodule size/vascularity, and intervention type such as RFA vs EA vs MIVAT/TOETVA), either through matching, stratification, or multivariable adjustment. Under Outcome, we prioritized precision and consistency of definitions (e.g., VRR formula, hormone thresholds), objective assessment (ultrasound parameters, laboratory assays), adequacy of follow-up for endocrine stabilization and recurrence, and completeness of outcome reporting including complications.
We also documented technical transparency (ultrasound guidance, energy settings, operator experience) as part of Selection/Outcome credibility because procedural clarity directly affects internal validity in device- and technique-driven studies. Each study could receive up to nine stars; consistent with our protocol, studies scoring < 5 were excluded, 5 - 6 were considered moderate quality, and ≥ 7 high quality. To reflect the reviewer’s request for visual clarity, we translated NOS domain judgments into traffic-light risk summaries and performed sensitivity analyses excluding lower-scoring studies to test robustness of pooled estimates. While we recognize NOS has limitations (e.g., less granular for single-arm designs), we mitigated this by adding topic-specific criteria (EBV confirmation, standardized outcome definitions, longitudinal follow-up, and protocol/operator transparency) so that quality ratings meaningfully captured the virology-procedural context of this review.
3.5. Protocol Transparency
The search strategy for this review was developed and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines by Page et al. (2021) (
20). All major steps, including database selection, keyword formulation, Boolean logic, and inclusion/exclusion criteria, were structured to meet PRISMA 2020 standards for transparency and reproducibility. The reference was incorporated as the methodological foundation guiding the formulation of search terms, screening workflow, and presentation of the PRISMA flow diagram in this study.
Although international registries such as PROSPERO promote transparency in prospective systematic reviews, registration was not required nor methodologically appropriate for the present investigation. This study synthesizes retrospectively available clinical data from published literature on EBV-associated thyroid disease and image-guided ablation outcomes, integrating both comparative and non-comparative observational studies.
PROSPERO’s scope is explicitly limited to prospectively designed reviews of interventional or exposure-effect relationships and excludes reviews that have already completed data collection, screening, or analysis. As our review was conceived after preliminary extraction and quality assessment of available reports, retrospective registration would provide no methodological safeguard against reporting bias and would in fact contravene PROSPERO’s eligibility criteria. Furthermore, PRISMA 2020 and the Cochrane Handbook specify that authors must report whether a protocol exists, but neither standard mandate formal registry submission. Instead, methodological transparency has been ensured through (1) strict adherence to PRISMA 2020 reporting items, (2) detailed disclosure of all inclusion/exclusion criteria and analytic procedures within this manuscript, and (3) public sharing of the full protocol and search strategy on the Open Science Framework (OSF). Hence, under the design, scope, and completion stage of this study, PROSPERO registration was not only unnecessary but ineligible, and transparency has been achieved through equally rigorous, open-access documentation consistent with international best practices.
3.6. Ultrasound Guidance and Technical Protocols
All procedures were conducted under real-time, high-frequency ultrasound guidance using linear probes (7 - 15 MHz) to ensure precise targeting and safety. Ablation parameters, including power output (watts), total energy delivery (joules), and frequency of application, were tailored according to nodule dimensions, vascularity, anatomical location, and proximity to critical structures such as the recurrent laryngeal nerve and carotid sheath. RFA was performed via percutaneous electrode insertion, with sequential energy delivery continued until uniform tissue hyperechogenicity and visible nodule shrinkage were achieved. EA involved ultrasound-guided intralesional injection of absolute ethanol, followed by continuous real-time monitoring to ensure homogeneous dispersion within the lesion. In select patients, MIVAT was used, utilizing small anterior cervical incisions to achieve targeted lesion excision while preserving surrounding glandular tissue and minimizing cosmetic impact.
3.7. Outcomes and Definitions
Primary Clinical Outcomes:
The VRR: Calculated as (Initial Volume - Final Volume)/Initial Volume × 100%
Hormonal Recovery: Defined as the normalization or significant improvement of serum TSH, FT3, and FT4 levels following the ablation procedure.
Complications: Included the incidence of hypothyroidism, hematoma, infection, transient or persistent voice changes, and any requirement for re-intervention.
Secondary Outcomes:
Cosmetic Outcomes: Assessed using patient- and physician-reported satisfaction scores, focusing on scar visibility, neck contour, and aesthetic appearance.
Hospital Stay Duration: Measured as the time from admission to discharge following the procedure.
Recurrence Rate: Defined as nodule regrowth or re-emergence of thyroid-related symptoms within 6 - 24 months of follow-up.
Patient Satisfaction and Quality of Life: When reported, subjective feedback regarding post-procedural comfort, recovery, and overall therapeutic acceptability was included to complement objective clinical data.
3.8. Data Sources and Nature of Evidence
The present investigation was conducted strictly as a systematic review and meta-analysis and did not involve the performance of any new laboratory tests, patient enrollment, or direct clinical experimentation. All biochemical, serological, and imaging data incorporated into the analysis were extracted exclusively from previously published peer-reviewed studies that had independently conducted these investigations. Laboratory parameters such as thyroid hormone concentrations (TSH, FT3, FT4), antibody titers, and EBV diagnostic profiles (including VCA-IgM, EBNA-IgG, or PCR detection of viral DNA) were recorded exactly as reported by the original authors. These variables were synthesized for comparative and pooled analysis to evaluate endocrine recovery, inflammatory response, and post-ablation outcomes across studies.
No human participants were recruited, and no additional biological sampling or testing was performed by the current authors. Ethical approval was therefore not required, as the review utilized secondary data already available in the scientific literature. To ensure full methodological transparency, all extracted laboratory information is explicitly referenced to its original source within the data-extraction framework. The article type has been clearly defined throughout the manuscript, including the title, abstract, and methods, as a Systematic Review and Meta-analysis, reflecting that the work is a secondary synthesis of published evidence rather than a primary laboratory or patient-based investigation.
3.9. Subgroup and Comparative Analyses
To characterize sources of variability, predefined subgroup analyses compared: (1) EBV-seropositive vs. EBV-seronegative individuals; (2) ablation modality (RFA vs. EA vs. MIVAT); (3) age category (≤ 18 vs. > 18 years, where stratified data were available); (4) sex-specific differences in procedural outcomes; and (5) nodule pathology (benign colloid nodules vs. lesions with suspicious cytology or inflammatory features).
3.10. Statistical Analysis
All statistical analyses were conducted using Stata/MP version 17.0 to ensure precision and reproducibility. A random-effects model based on the DerSimonian and Laird method was selected because the included studies varied in their design, population characteristics, intervention modalities, and follow-up durations, making between-study variability inevitable. The random-effects approach assumes that the true effect size may differ across studies and provides more conservative pooled estimates compared to fixed-effects models.
For outcome synthesis, pooled odds ratios (ORs) were computed for dichotomous variables (e.g., complication rates, recurrence, or treatment success), while standardized mean differences (SMDs) were calculated for continuous outcomes (e.g., nodule volume reduction, hormone normalization, or hospital stay duration). Each pooled estimate was accompanied by a 95% confidence interval (CI), and forest plots were generated to visualize individual and overall effect sizes, enhancing interpretability of consistency and weight contribution across studies.
To assess statistical heterogeneity, both Cochran’s Q test (with p < 0.10 indicating significance) and the I² statistic were applied. An I² value of 0 - 25% was interpreted as low heterogeneity, 26 - 50% as moderate, and > 50% as substantial heterogeneity. When high heterogeneity was observed, potential sources were explored through subgroup analyses and sensitivity analyses. Subgroups were pre-specified according to clinically meaningful categories: age group (pediatric/adolescent ≤ 18 years vs. adult > 18 years), disease type (Graves’ disease, Hashimoto’s thyroiditis, or benign nodular lesions), and type of intervention [RFA, EA, MIVAT, TOETVA, gasless transaxillary thyroidectomy (GTET), or bilateral axillo-breast approach (BABA)]. Subgroup analyses were performed by stratified pooling and between-group heterogeneity was tested using the Cochran Q statistic for subgroup differences. For categorical event rates such as postoperative complications, Mantel-Haenszel weighting was applied, as it provides reliable pooled ORs even when event rates are low. Continuous data were synthesized using the inverse-variance method, which assigns weights proportional to the precision of each study’s effect estimate.
Publication bias was assessed using both funnel plots and Egger’s regression test. Funnel plots were visually inspected for asymmetry, which can indicate selective publication or small-study effects, while Egger’s test provided a quantitative measure of asymmetry, with p < 0.05 suggesting potential bias. When asymmetry was detected, a trim-and-fill analysis was considered to evaluate its potential influence on the pooled effect. To verify robustness, sensitivity analyses were performed by sequentially excluding low-quality or high-risk-of-bias studies (as determined by the NOS) and recalculating pooled estimates to assess the stability of findings. All statistical tests were two-tailed, and p < 0.05 was considered statistically significant. This comprehensive statistical framework, incorporating heterogeneity evaluation, subgroup stratification, bias diagnostics, and sensitivity testing, ensured that pooled results were not only statistically sound but also clinically meaningful and transparent in reflecting the variability of evidence within this multidisciplinary dataset on EBV-associated thyroid ablation outcomes.