In thyroid eye disease (Graves' orbitopathy), the MOST reliable indicator of disease activity for treatment planning is:
- A TSH receptor antibody titre (TRAb)
- B Degree of proptosis on Hertel exophthalmometry
- C Clinical Activity Score (CAS) ≥ 3/7 ✓
- D Serum free T4 level
Correct answer: C. Clinical Activity Score (CAS) ≥ 3/7
Explanation
The Clinical Activity Score (CAS) evaluates seven inflammatory signs (pain, redness, swelling, impaired function) and a CAS ≥ 3/7 (or ≥ 4/10 in the extended version) indicates active disease likely to respond to immunosuppression. TRAb levels indicate disease severity and risk of recurrence but are less reliable for activity. Proptosis (exophthalmos) measures anatomical extent, not inflammatory activity. Free T4 reflects thyroid function, not orbital disease activity.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.