Study of Biochemical, Ultrasonographical, and Scintigraphical Features in the Etiological Diagnosis of Thyrotoxicosis

Background: Thyrotoxicosis, a clinical syndrome with diverse etiologies, demands accurate differentiation between Graves’ disease (GD) and destructive thyroiditis (DT) to guide appropriate management. Overlapping clinical and biochemical features often complicate diagnosis, especially in milder cases and in resource-limited settings. Objective: To evaluate the diagnostic accuracy of three commonly used modalities—technetium- 99 m pertechnetate 99 mTc thyroid uptake, thyrotropin receptor antibodies (TRAb), and color flow Doppler ultrasonography (CFD-USG)—in differentiating GD from DT, and to propose a simplified, resource-adaptable diagnostic algorithm. Methods: This prospective observational study included patients presenting with thyrotoxicosis. Clinical data, 99 mTc uptake values, TRAb levels, and CFD-USG parameters including peak systolic velocity of the inferior thyroid artery (PSV-ITA) were recorded. Diagnostic performance of each modality was analyzed using standard statistical methods and compared against final clinical diagnoses. Results: 99 mTc uptake and TRAb showed high sensitivity and specificity individually, with near-perfect diagnostic accuracy when combined. TRAb levels >3 IU/L reliably diagnosed GD, while levels between 1.5–3 IU/L required CFD-USG for clarification. PSV-ITA demonstrated high specificity but limited sensitivity, making it suitable as a ’rule-in’ test. T3/T4 ratio had the lowest diagnostic utility. A combined, tiered diagnostic approach based on available resources was found to be both effective and cost-efficient. Conclusion: No single modality is universally definitive; however, an integrated diagnostic pathway leveraging TRAb, 99 mTc uptake, and CFD-USG enhances diagnostic confidence. This approach aligns with international guidelines and is adaptable across diverse clinical settings.