How many hospitals were involved in the initial examination?

• A. 28
• B. 39
• C. 14
• D. 50

Answer: (B)

Baseline sample size is the number of hospitals that started the study and underwent the initial examination. This figure comes from the methods description where the study first describes who was included before any follow-up or exclusions. In this item, the record specifies that 39 hospitals participated at the initial examination, so that count reflects the initial phase of data collection. Other numbers typically relate to later stages—centers that were added after baseline, or sites excluded due to missing data or follow-up issues—so they don’t represent the initial examination. When answering, look for phrasing like “at baseline” or “initial examination” to identify the initial sample size.