Which of the following is a characteristic feature that distinguishes a double-blind RCT from a single-blind RCT?

Explanation

## Blinding in RCTs: Single-Blind vs Double-Blind ### Definition of Blinding Levels **Key Point:** Blinding refers to masking knowledge of treatment assignment from individuals who could introduce bias. The number of "blinds" indicates how many parties are masked. ### Comparison of Blinding Structures | Type | Participants Blinded | Investigators/Assessors Blinded | Outcome Assessors Blinded | |------|----------------------|----------------------------------|---------------------------| | **Single-Blind** | Yes | No | No | | **Double-Blind** | Yes | Yes (or outcome assessors) | Yes | | **Triple-Blind** | Yes | Yes | Yes (+ data analysts) | ### What "Double-Blind" Means **High-Yield:** In a double-blind RCT, **both the participants AND the outcome assessors (or investigators)** are unaware of treatment assignment. This prevents: 1. **Performance bias** — participants altering their behavior based on perceived treatment 2. **Detection bias** — assessors measuring outcomes differently based on knowledge of treatment **Clinical Pearl:** Double-blinding is considered the gold standard for subjective outcomes (pain, symptoms, quality of life) because it prevents both placebo effects and assessment bias. For objective outcomes (mortality, laboratory values), blinding of outcome assessors is still critical. **Mnemonic:** **2B** — Double-Blind = 2 Blinded parties (Participants + outcome Assessors/Investigators).