Agreement between the two blinded reviewers was excellent. The quadratic weighted kappa for concordance scoring was 0.914 (95% CI, 0.835 to 0.967), with 94.0% exact agreement across 300 responses and no 2-point disagreements (Table 1).
Table 1. Overall guideline concordance and inter-rater reliability by prompt strategy
| n | Concordant (score 2) | Partial (score 1) | Discordant (score 0) | Mean score | κw (95% CI) | % Agreement |
| Prompt A (Baseline) | 100 | 77 (77.0%) | 14 (14.0%) | 9 (9.0%) | 1.68 | 0.909 (0.823–0.967) | 93.0% |
| Prompt B (Role-play) | 100 | 80 (80.0%) | 13 (13.0%) | 7 (7.0%) | 1.73 | 0.907 (0.812–0.972) | 94.0% |
| Prompt C (Chain-of-thought) | 100 | 79 (79.0%) | 14 (14.0%) | 7 (7.0%) | 1.72 | 0.926 (0.836–0.984) | 95.0% |
| Overall | 300 | 236 (78.7%) | 41 (13.7%) | 23 (7.7%) | 1.71 | 0.914 (0.835–0.967) | 94.0% |
Concordance scores represent consensus between two blinded reviewers. κw = quadratic weighted Cohen’s kappa. Friedman test: χ²=1.23, p = 0.54 (no significant difference between prompt strategies).
Weighted-kappa 95% confidence intervals were obtained by bootstrapping over questions. Friedman test df=2; because most questions were scored identically across prompts, the ranks were heavily tied.
Of the 300 responses, 236 (78.7%; 95% confidence interval [CI], 73.7% to 82.9%) were fully concordant with the guideline, 41 (13.7%) were partially concordant, and 23 (7.7%) were discordant (Table 1; Supplementary Table S7). Thus, roughly four of five outputs aligned fully with guideline recommendations, whereas about one in thirteen contradicted them.
The prompt strategy did not materially change performance. Full concordance was 77% with baseline prompting, 80% with role-play, and 79% with chain-of-thought. In the primary Bayesian model, the role-play and chain-of-thought odds ratios both had 95% credible intervals that included 1, and cross-validation did not favor a model with prompt. The result was unchanged in supportive analyses, including the Friedman test (χ²=1.23, p = 0.54) and the binary cluster-robust sensitivity model (Wald χ²=0.99, p = 0.61) (Figure 1B).
Concordance varied across domains at the descriptive level. Follow-up had the highest full concordance rate at 93.3%, whereas epidemiology had the lowest at 71.1% and also the highest discordance rate at 20.0%. This variation did not survive the structure of the data. Eighty-one of the 100 questions were scored identically across all three prompts. Most of the variance therefore lay between questions, not between domains or prompts. The intraclass correlation was high (0.87; 95% credible interval, 0.78 to 0.93). The random-intercept standard deviation was large and weakly identified (posterior median ≈4.7 on the logit scale; prior-sensitive, Supplementary Table S6). In the primary Bayesian model, every domain odds ratio had a 95% credible interval that included 1. The overall domain effect was not significant by likelihood-ratio test (χ²=9.19, df=4, p = 0.06), and cross-validation did not distinguish the model with domain from the model without it. Domain is a between-question characteristic, and only 19 questions varied across prompts. The study had limited power to resolve a domain effect (Table 2, Panel A; Figure 1A; Supplementary Table S8; Supplementary Figure S2).
Table 2. Primary and sensitivity regression analyses for guideline concordance
| Panel A. Mixed-effects ordinal logistic regression* |
| Fixed effect | χ² (LRT) | df | p-value | | |
| Domain (overall) | 9.19 | 4 | 0.06 | | |
| Prompt strategy (overall) | 1.60 | 2 | 0.45 | | |
| Random-intercept SD (σ), posterior median (95% CrI) | 4.7 (3.4–6.6) | | | | |
| Intraclass correlation (95% CrI) | 0.87 (0.78–0.93) | | | | |
| Panel B. Binary cluster-robust logistic regression (sensitivity analysis)† |
| Variable | Full concordance (%) | OR | 95% CI | p-value | Wald test‡ |
| Domain | | | | | χ²=4.84, p = 0.30 |
| Follow-up (ref.) | 93.3 | 1.00 | — | — | |
| Epidemiology | 71.1 | 0.20 | 0.05–0.64 | — | |
| TNM | 88.3 | 0.59 | 0.14–2.11 | — | |
| Diagnosis | 73.3 | 0.22 | 0.06–0.69 | — | |
| Treatment | 72.2 | 0.21 | 0.05–0.62 | — | |
| Prompt strategy | | | | | χ²=0.99, p = 0.61 |
| Baseline (ref.) | 77.0 | 1.00 | — | — | |
| Role-play | 80.0 | 1.19 | 0.84–1.70 | 0.32 | |
| Chain-of-thought | 79.0 | 1.12 | 0.75–1.67 | 0.57 | |
*Mixed-effects ordinal logistic regression (proportional odds) with concordance score (0,1,2) as outcome, domain and prompt as fixed effects, question ID as random intercept. In the primary analysis the model was fitted by Bayesian estimation with weakly-informative priors; a maximum-likelihood fit with adaptive Gauss-Hermite quadrature (25 nodes) served as a sensitivity analysis. Individual domain odds ratios are not reported because the large, weakly-identified random-intercept variance renders conditional odds ratios unstable. Overall effects are assessed by likelihood-ratio χ² test and by leave-one-out cross-validation; Panel A gives the posterior random-intercept standard deviation (prior-sensitive; Supplementary Table S6) and the intraclass correlation. †Binary logistic regression (fully concordant [score 2] vs not fully concordant [score 0 or 1]) with cluster-robust (sandwich) standard errors, clustered by question ID. Domain odds ratios are Firth-penalized to remain finite under the near-ceiling reference domain; this marginal model treats the 300 responses as independent, whereas every domain 95% credible interval in the primary clustered model included 1. OR <1 indicates lower odds of full concordance relative to the reference category. ‡Overall Wald chi-square test. Descriptive concordance rates by domain and prompt are provided in Supplementary Table S8.
The response-level analyses pointed the other way. The Kruskal-Wallis test was nominally significant (H=13.95, df=4, p = 0.007), and a Firth-penalized logistic model placed the odds of full concordance below follow-up for epidemiology, diagnosis, and treatment (Table 2, Panel B). That model treats the 300 responses as independent. It ignores the three responses clustered within each question, and it overstates the precision of a between-question contrast. Once the clustering was restored, the domain effect did not survive. The domain gradient is suggestive, not established.
Question type was not associated with concordance. Action-oriented questions did not perform differently from definition/classification items in either the descriptive comparison (Mann-Whitney p = 0.41) or the cluster-robust model (OR=1.24; 95% CI, 0.52–2.97; p = 0.62). The recommendation strength also did not explain model performance. Strong recommendations had a lower mean concordance than weak recommendations (1.61 versus 1.82), but the difference was not statistically significant in either the descriptive analysis (p = 0.20) or the cluster-robust model (OR for weak versus strong, 2.19; 95% CI, 0.50–9.52; p = 0.30; Supplementary Table S9).
Among the 64 consensus non-concordant responses, omission and reasoning failures predominated. Both reviewers identified similar error distributions. Reviewer 1 classified 46.9% as omission, 37.5% as reasoning errors, and 15.6% as hallucinations. Reviewer 2 classified 48.4% as omission, 37.5% as reasoning errors, and 14.1% as hallucinations. Averaging across reviewers, omission accounted for 47.7% of all errors, reasoning for 37.5%, and hallucination for 14.8% (Table 3; Figure 2A).
Table 3. Error taxonomy by clinical domain — dual-reviewer classification (n = 64 consensus non-concordant responses)
| | Reviewer 1 | Reviewer 2 |
| Clinical domain | n | Hallucination n (%) | Omission n (%) | Reasoning n (%) | Hallucination n (%) | Omission n (%) | Reasoning n (%) |
| Epidemiology | 13 | 3 (23.1%) | 4 (30.8%) | 6 (46.2%) | 2 (15.4%) | 4 (30.8%) | 7 (53.8%) |
| TNM | 7 | 1 (14.3%) | 3 (42.9%) | 3 (42.9%) | 1 (14.3%) | 3 (42.9%) | 3 (42.9%) |
| Diagnosis | 16 | 3 (18.8%) | 5 (31.2%) | 8 (50.0%) | 3 (18.8%) | 5 (31.2%) | 8 (50.0%) |
| Treatment | 25 | 3 (12.0%) | 15 (60.0%) | 7 (28.0%) | 0 (0.0%) | 19 (76.0%) | 6 (24.0%) |
| Follow-up | 3 | 0 (0.0%) | 3 (100.0%) | 0 (0.0%) | 3 (100.0%) | 0 (0.0%) | 0 (0.0%) |
| Total | 64 | 10 (15.6%) | 30 (46.9%) | 24 (37.5%) | 9 (14.1%) | 31 (48.4%) | 24 (37.5%) |
Error types based on consensus non-concordant responses (concordance score 0 or 1). Both reviewers independently classified errors. Inter-rater agreement on error type: Cohen’s kappa=0.795 (87.5% agreement). Hallucination = fabricated clinical data absent from guidelines; Omission = failure to include critical guideline-specified information; Reasoning = correct facts leading to incorrect clinical conclusion. Prevalence-adjusted kappa = 0.81. Category-specific agreement (kappa): hallucination 0.57 (95% CI, 0.24–0.84), omission 0.78, reasoning 0.93. The follow-up cell reflects a single question (ID 96), scored as omission by one reviewer and hallucination by the other, and should not be over-interpreted.
Agreement on error type was substantial overall (Cohen’s kappa=0.795; prevalence-adjusted kappa=0.81), but it varied by category. It was least reliable for hallucination (category-specific kappa=0.57; 95% CI, 0.24 to 0.84). Agreement was lowest in follow-up. There, the three non-concordant responses came from one question, which one reviewer scored as omission and the other as hallucination. That single cell should not be read as a stable estimate.
The distribution of errors differed by domain (Figure 2B; Supplementary Table S10). In treatment, omission dominated and accounted for 68.0% of errors. These responses often identified the correct therapeutic direction but omitted critical details specified in the guideline, such as saphenous vein sparing or thresholds for pelvic lymph node dissection. In epidemiology, reasoning errors were most common, accounting for 50.0% of errors, followed by omission (30.8%) and hallucination (19.2%). The hallucinations in this domain involved fabricated numerical estimates for phimosis and smoking risk. Diagnosis also showed a predominance of reasoning errors (50.0%), and TNM classification showed a similar pattern (42.9%).
The most stable feature of the dataset was not the prompt but the question. Eighty-one of 100 questions received identical consensus scores across all three prompting conditions. Seventy-two questions were uniformly concordant, five were uniformly partial, and four were uniformly discordant. The remaining 19 showed mixed performance across prompts.
The uniformly discordant questions were clinically revealing. They included fabricated biopsy specifications, incorrect claims regarding p16 and human papillomavirus (HPV) testing recommendations, and refusal to provide published diagnostic accuracy data. These failures persisted regardless of prompt strategy (Supplementary Tables S11 and S12). Cross-prompt consistency was high overall: 79% of questions received the maximum consistency score. Concordance and consistency were positively correlated (Spearman rho=0.726, p < 0.001). Notably, the uniformly discordant questions also received perfect consistency scores, showing that some incorrect answers were not only wrong, but stably wrong.
RESULTS
Agreement between the two blinded reviewers was excellent. The quadratic weighted kappa for concordance scoring was 0.914 (95% CI, 0.835 to 0.967), with 94.0% exact agreement across 300 responses and no 2-point disagreements (Table 1).
Table 1. Overall guideline concordance and inter-rater reliability by prompt strategy
| n | Concordant (score 2) | Partial (score 1) | Discordant (score 0) | Mean score | κw (95% CI) | % Agreement |
| Prompt A (Baseline) | 100 | 77 (77.0%) | 14 (14.0%) | 9 (9.0%) | 1.68 | 0.909 (0.823–0.967) | 93.0% |
| Prompt B (Role-play) | 100 | 80 (80.0%) | 13 (13.0%) | 7 (7.0%) | 1.73 | 0.907 (0.812–0.972) | 94.0% |
| Prompt C (Chain-of-thought) | 100 | 79 (79.0%) | 14 (14.0%) | 7 (7.0%) | 1.72 | 0.926 (0.836–0.984) | 95.0% |
| Overall | 300 | 236 (78.7%) | 41 (13.7%) | 23 (7.7%) | 1.71 | 0.914 (0.835–0.967) | 94.0% |
Concordance scores represent consensus between two blinded reviewers. κw = quadratic weighted Cohen’s kappa. Friedman test: χ²=1.23, p = 0.54 (no significant difference between prompt strategies).
Weighted-kappa 95% confidence intervals were obtained by bootstrapping over questions. Friedman test df=2; because most questions were scored identically across prompts, the ranks were heavily tied.
Of the 300 responses, 236 (78.7%; 95% confidence interval [CI], 73.7% to 82.9%) were fully concordant with the guideline, 41 (13.7%) were partially concordant, and 23 (7.7%) were discordant (Table 1; Supplementary Table S7). Thus, roughly four of five outputs aligned fully with guideline recommendations, whereas about one in thirteen contradicted them.
The prompt strategy did not materially change performance. Full concordance was 77% with baseline prompting, 80% with role-play, and 79% with chain-of-thought. In the primary Bayesian model, the role-play and chain-of-thought odds ratios both had 95% credible intervals that included 1, and cross-validation did not favor a model with prompt. The result was unchanged in supportive analyses, including the Friedman test (χ²=1.23, p = 0.54) and the binary cluster-robust sensitivity model (Wald χ²=0.99, p = 0.61) (Figure 1B).
Concordance varied across domains at the descriptive level. Follow-up had the highest full concordance rate at 93.3%, whereas epidemiology had the lowest at 71.1% and also the highest discordance rate at 20.0%. This variation did not survive the structure of the data. Eighty-one of the 100 questions were scored identically across all three prompts. Most of the variance therefore lay between questions, not between domains or prompts. The intraclass correlation was high (0.87; 95% credible interval, 0.78 to 0.93). The random-intercept standard deviation was large and weakly identified (posterior median ≈4.7 on the logit scale; prior-sensitive, Supplementary Table S6). In the primary Bayesian model, every domain odds ratio had a 95% credible interval that included 1. The overall domain effect was not significant by likelihood-ratio test (χ²=9.19, df=4, p = 0.06), and cross-validation did not distinguish the model with domain from the model without it. Domain is a between-question characteristic, and only 19 questions varied across prompts. The study had limited power to resolve a domain effect (Table 2, Panel A; Figure 1A; Supplementary Table S8; Supplementary Figure S2).
Table 2. Primary and sensitivity regression analyses for guideline concordance
| Panel A. Mixed-effects ordinal logistic regression* |
| Fixed effect | χ² (LRT) | df | p-value | | |
| Domain (overall) | 9.19 | 4 | 0.06 | | |
| Prompt strategy (overall) | 1.60 | 2 | 0.45 | | |
| Random-intercept SD (σ), posterior median (95% CrI) | 4.7 (3.4–6.6) | | | | |
| Intraclass correlation (95% CrI) | 0.87 (0.78–0.93) | | | | |
| Panel B. Binary cluster-robust logistic regression (sensitivity analysis)† |
| Variable | Full concordance (%) | OR | 95% CI | p-value | Wald test‡ |
| Domain | | | | | χ²=4.84, p = 0.30 |
| Follow-up (ref.) | 93.3 | 1.00 | — | — | |
| Epidemiology | 71.1 | 0.20 | 0.05–0.64 | — | |
| TNM | 88.3 | 0.59 | 0.14–2.11 | — | |
| Diagnosis | 73.3 | 0.22 | 0.06–0.69 | — | |
| Treatment | 72.2 | 0.21 | 0.05–0.62 | — | |
| Prompt strategy | | | | | χ²=0.99, p = 0.61 |
| Baseline (ref.) | 77.0 | 1.00 | — | — | |
| Role-play | 80.0 | 1.19 | 0.84–1.70 | 0.32 | |
| Chain-of-thought | 79.0 | 1.12 | 0.75–1.67 | 0.57 | |
*Mixed-effects ordinal logistic regression (proportional odds) with concordance score (0,1,2) as outcome, domain and prompt as fixed effects, question ID as random intercept. In the primary analysis the model was fitted by Bayesian estimation with weakly-informative priors; a maximum-likelihood fit with adaptive Gauss-Hermite quadrature (25 nodes) served as a sensitivity analysis. Individual domain odds ratios are not reported because the large, weakly-identified random-intercept variance renders conditional odds ratios unstable. Overall effects are assessed by likelihood-ratio χ² test and by leave-one-out cross-validation; Panel A gives the posterior random-intercept standard deviation (prior-sensitive; Supplementary Table S6) and the intraclass correlation. †Binary logistic regression (fully concordant [score 2] vs not fully concordant [score 0 or 1]) with cluster-robust (sandwich) standard errors, clustered by question ID. Domain odds ratios are Firth-penalized to remain finite under the near-ceiling reference domain; this marginal model treats the 300 responses as independent, whereas every domain 95% credible interval in the primary clustered model included 1. OR <1 indicates lower odds of full concordance relative to the reference category. ‡Overall Wald chi-square test. Descriptive concordance rates by domain and prompt are provided in Supplementary Table S8.
The response-level analyses pointed the other way. The Kruskal-Wallis test was nominally significant (H=13.95, df=4, p = 0.007), and a Firth-penalized logistic model placed the odds of full concordance below follow-up for epidemiology, diagnosis, and treatment (Table 2, Panel B). That model treats the 300 responses as independent. It ignores the three responses clustered within each question, and it overstates the precision of a between-question contrast. Once the clustering was restored, the domain effect did not survive. The domain gradient is suggestive, not established.
Question type was not associated with concordance. Action-oriented questions did not perform differently from definition/classification items in either the descriptive comparison (Mann-Whitney p = 0.41) or the cluster-robust model (OR=1.24; 95% CI, 0.52–2.97; p = 0.62). The recommendation strength also did not explain model performance. Strong recommendations had a lower mean concordance than weak recommendations (1.61 versus 1.82), but the difference was not statistically significant in either the descriptive analysis (p = 0.20) or the cluster-robust model (OR for weak versus strong, 2.19; 95% CI, 0.50–9.52; p = 0.30; Supplementary Table S9).
Among the 64 consensus non-concordant responses, omission and reasoning failures predominated. Both reviewers identified similar error distributions. Reviewer 1 classified 46.9% as omission, 37.5% as reasoning errors, and 15.6% as hallucinations. Reviewer 2 classified 48.4% as omission, 37.5% as reasoning errors, and 14.1% as hallucinations. Averaging across reviewers, omission accounted for 47.7% of all errors, reasoning for 37.5%, and hallucination for 14.8% (Table 3; Figure 2A).
Table 3. Error taxonomy by clinical domain — dual-reviewer classification (n = 64 consensus non-concordant responses)
| | Reviewer 1 | Reviewer 2 |
| Clinical domain | n | Hallucination n (%) | Omission n (%) | Reasoning n (%) | Hallucination n (%) | Omission n (%) | Reasoning n (%) |
| Epidemiology | 13 | 3 (23.1%) | 4 (30.8%) | 6 (46.2%) | 2 (15.4%) | 4 (30.8%) | 7 (53.8%) |
| TNM | 7 | 1 (14.3%) | 3 (42.9%) | 3 (42.9%) | 1 (14.3%) | 3 (42.9%) | 3 (42.9%) |
| Diagnosis | 16 | 3 (18.8%) | 5 (31.2%) | 8 (50.0%) | 3 (18.8%) | 5 (31.2%) | 8 (50.0%) |
| Treatment | 25 | 3 (12.0%) | 15 (60.0%) | 7 (28.0%) | 0 (0.0%) | 19 (76.0%) | 6 (24.0%) |
| Follow-up | 3 | 0 (0.0%) | 3 (100.0%) | 0 (0.0%) | 3 (100.0%) | 0 (0.0%) | 0 (0.0%) |
| Total | 64 | 10 (15.6%) | 30 (46.9%) | 24 (37.5%) | 9 (14.1%) | 31 (48.4%) | 24 (37.5%) |
Error types based on consensus non-concordant responses (concordance score 0 or 1). Both reviewers independently classified errors. Inter-rater agreement on error type: Cohen’s kappa=0.795 (87.5% agreement). Hallucination = fabricated clinical data absent from guidelines; Omission = failure to include critical guideline-specified information; Reasoning = correct facts leading to incorrect clinical conclusion. Prevalence-adjusted kappa = 0.81. Category-specific agreement (kappa): hallucination 0.57 (95% CI, 0.24–0.84), omission 0.78, reasoning 0.93. The follow-up cell reflects a single question (ID 96), scored as omission by one reviewer and hallucination by the other, and should not be over-interpreted.
Agreement on error type was substantial overall (Cohen’s kappa=0.795; prevalence-adjusted kappa=0.81), but it varied by category. It was least reliable for hallucination (category-specific kappa=0.57; 95% CI, 0.24 to 0.84). Agreement was lowest in follow-up. There, the three non-concordant responses came from one question, which one reviewer scored as omission and the other as hallucination. That single cell should not be read as a stable estimate.
The distribution of errors differed by domain (Figure 2B; Supplementary Table S10). In treatment, omission dominated and accounted for 68.0% of errors. These responses often identified the correct therapeutic direction but omitted critical details specified in the guideline, such as saphenous vein sparing or thresholds for pelvic lymph node dissection. In epidemiology, reasoning errors were most common, accounting for 50.0% of errors, followed by omission (30.8%) and hallucination (19.2%). The hallucinations in this domain involved fabricated numerical estimates for phimosis and smoking risk. Diagnosis also showed a predominance of reasoning errors (50.0%), and TNM classification showed a similar pattern (42.9%).
The most stable feature of the dataset was not the prompt but the question. Eighty-one of 100 questions received identical consensus scores across all three prompting conditions. Seventy-two questions were uniformly concordant, five were uniformly partial, and four were uniformly discordant. The remaining 19 showed mixed performance across prompts.
The uniformly discordant questions were clinically revealing. They included fabricated biopsy specifications, incorrect claims regarding p16 and human papillomavirus (HPV) testing recommendations, and refusal to provide published diagnostic accuracy data. These failures persisted regardless of prompt strategy (Supplementary Tables S11 and S12). Cross-prompt consistency was high overall: 79% of questions received the maximum consistency score. Concordance and consistency were positively correlated (Spearman rho=0.726, p < 0.001). Notably, the uniformly discordant questions also received perfect consistency scores, showing that some incorrect answers were not only wrong, but stably wrong.