Vitreous humour glucose and lactate kinetics in a hospital forensic cohort.

BACKGROUND: The inverse relationship between vitreous humour (VH) glucose and lactate, classically used in the Traub formula, is widely applied in post-mortem biochemistry. METHODS: We analysed 127 VH samples from external examinations and forensic autopsies performed in a hospital forensic setting (PMI 4-187 h; 58 septic and 69 non-septic deaths). Glucose was available in 78 cases, lactic acid in all 127. Cases were stratified by PMI window, septic status and storage condition. Spearman correlations and non-parametric comparisons were applied. RESULTS: Within the first 24 h post-mortem, glucose and lactic acid showed significant opposite correlations with PMI. Glucose reached a low-value floor of approximately 2 mg/dl by 25-48 h, after which no meaningful PMI-related decrease was observed. Lactic acid showed a different trajectory: septic and non-septic cases had similar baseline levels at ≤10 h, but diverged thereafter, with continued increase in septic cases through 25-48 h. This divergence emerged after glucose depletion, suggesting glucose-independent lactate accumulation. Glucose-lactate coupling was absent in septic cases and weak in non-septic cases. CONCLUSIONS: VH glucose and lactic acid showed limited evidence of direct stoichiometric coupling in this hospital cohort. Glucose reflected PMI mainly within the first 24 h, whereas its interpretative value declined after reaching a post-mortem floor. Lactic acid showed a sepsis-associated post-mortem amplification not explained by glucose availability alone, possibly reflecting autolytic processes. These findings do not invalidate the Traub formula in its original diagnostic context, but caution against its uncritical application in heterogeneous forensic cohorts.