Which is considered the lowest level of evidence?

Which is considered the lowest level of evidence?

• A. Expert opinion
• B. Narrative reviews
• C. Studies of single cases
• D. Personal experiences in practice

Answer: (A)

In evidence-based practice, the strength of evidence rests on how rigorously a claim is studied. The lowest level is expert opinion because it relies on the judgments or beliefs of a single clinician or authority without systematic data, methods, or testing. This means the conclusions can be highly biased, not reproducible, and not generalizable to broader patient populations. While case reports, narrative reviews, and personal practice experiences can offer useful observations, they do not provide the same level of validated, generalizable evidence as well-designed studies, systematic reviews, or trials.

In evidence-based practice, the strength of evidence rests on how rigorously a claim is studied. The lowest level is expert opinion because it relies on the judgments or beliefs of a single clinician or authority without systematic data, methods, or testing. This means the conclusions can be highly biased, not reproducible, and not generalizable to broader patient populations. While case reports, narrative reviews, and personal practice experiences can offer useful observations, they do not provide the same level of validated, generalizable evidence as well-designed studies, systematic reviews, or trials.