Human evaluators vs. LLM-as-a-Judge: toward scalable evaluation of GenAI in global health.
Evaluating generative AI output remains a critical bottleneck for safe and scalable deployment of AI in healthcare. Expert clinical judgement is often presented as the gold standard, but human assessment is costly and inconsistent. LLM-as-judge systems, i.e., leveraging AI to evaluate other AI outputs, have been proposed, yet their reliability in global health remains untested. We compared five LLM judges and six human clinicians in evaluating responses to questions posed by Rwandan health workers. The highest-performing LLM-judge (Claude-4.1-Opus) matched human evaluators on only four of eleven evaluation criteria, with other models scoring too leniently (Gemini-2.5-Pro) or too harshly (GPT-5). Constructing LLM-juries to balance model-specific biases improved agreement on only one additional criterion. Notably, performance and cost-effectiveness fell when moving from English to Kinyarwanda. Overall, while LLM-judges show promise, their inability to handle linguistic and cultural context is a critical limitation, underscoring the need for further investment in scalable evaluation solutions.