[Study on the correlation between PMI and OD changes in rat's plasma].

The review approach involved analyzing 150 female Sprague-Dawley rats to observe postmortem changes. Investigators sacrificed all subjects via cervical dislocation to ensure a uniform starting point. Bodies remained within a chamber maintained at 20 degrees Celsius throughout the trial. Technicians harvested plasma samples at various intervals from zero to 24 hours. The team utilized a UV250 spectrophotometer to determine light absorption levels. Researchers focused on three distinct wavelengths to capture spectral variations in the fluid. They calculated regression formulas to link optical density readings with elapsed time. This systematic design allowed for the derivation of quadratic equations for each wavelength.

The strongest finding demonstrates that optical density at 416 nm exhibits a high correlation with time, reaching an R-index of 0.97. Data at 577 nm showed a similarly strong correlation with an R-index of 0.969. Measurements at 275 nm yielded an R-index of 0.898, indicating a slightly lower but still significant relationship. The researchers derived quadratic regression equations for all three wavelengths to predict the postmortem interval. The formula for 577 nm achieved an R-squared value of 0.945. The equation for 416 nm resulted in an R-squared value of 0.94. The model for 275 nm produced an R-squared value of 0.795. These results confirm that plasma absorption shifts are strongly linked to the time elapsed since death.

The authors suggest that plasma light absorption serves as a viable indicator for temporal estimation. Their synthesis indicates that specific wavelengths provide distinct correlation strengths for postmortem timing. The researchers propose that these mathematical models could enhance current forensic methodologies. This work implies that plasma analysis offers a non-invasive pathway for future death investigations. The findings confirm that optical density shifts track consistently with the progression of time. These results support the integration of spectrophotometric data into standard postmortem protocols. The authors emphasize the potential utility of these specific wavelengths in practical field applications. Future efforts might refine these regression formulas for broader forensic implementation.