Biochemical analysis of vitreous humor and synovial fluid in the estimation of early postmortem interval: A meta-analytical approach

The estimation of the postmortem interval (PMI) is a significant challenge in legal medicine and forensic sciences due to the dynamic and continuous decomposition of organisms after death. Thanatochemistry has emerged as a promising area to estimate PMI by measuring the concentrations of postmortem biochemical markers. This systematic review and meta-analysis aimed to summarize evidence on postmortem biochemical alterations in vitreous humor (VH) and synovial fluid (SF) to estimate early PMI. Comprehensive searches of electronic databases identified studies measuring postmortem biomarker concentrations in both matrices. Our analysis included three meta-analytical approaches: calculating standardized mean differences to assess variations in biochemical parameters, executing correlation meta-analysis (ρ) to explore relationships between these parameters and PMI, and conducting meta-regression to derive a predictive model. Results from five eligible studies indicated no correlation between sodium levels and PMI in both matrices. However, a strong correlation was found between potassium levels and PMI in VH (ρ = 0.69; 95 % CI 0.52 to 0.86) and SF (ρ = 0.81; 95 % CI 0.75 to 0.87), with the meta-regression yielding the optimal predictive equation for SF: [K+] = 6.15 + 0.21 × PMI. These findings support the use of potassium as a reliable biomarker for PMI estimation, particularly in SF.