Comparing the diagnostic utility of the Pleural Effusion Ratio and the Drowning Index in identifying freshwater drowning deaths

Abstract

Background

Diagnosing drowning during post-mortem examination remains a challenging task due to the absence of any pathognomonic autopsy findings. Recent approaches have proposed quantitative indices, such as the Pleural Effusion Ratio (PE Ratio) and the Drowning Index (DI), to enhance diagnostic accuracy. The PE Ratio is defined as the weight of the pleural effusion divided by the combined weight of the pleural effusion and lungs, multiplied by 100. The DI is defined as the sum of the lung weight and pleural effusion weight, divided by the spleen weight.

Methods

This prospective cross-sectional autopsy study evaluated 179 medico-legal cases, comprising 75 freshwater drowning cases, 64 sudden cardiac deaths, and 40 hangings. All drowning incidents occurred in a glacier-fed river under uniform environmental conditions. The PE Ratio and DI were calculated using organ and pleural effusion weights. Statistical analysis included ANOVA, Kruskal–Wallis tests, post hoc testing, and Receiver Operating Characteristic (ROC) curve analysis.

Results

The PE Ratio showed a mean value of 29.57 in drowning cases and demonstrated perfect diagnostic performance, with an AUC of 1.0, achieving 100 % sensitivity and specificity at a cut-off value of >7.4. The DI also showed a significant elevation in drowning cases (mean: 14.8) compared to controls, yielding an AUC of 0.828, with 86.7 % sensitivity and 70.2 % specificity at a cut-off value of >9.7.

Conclusion

The PE Ratio is a simple, robust, and highly accurate tool for diagnosing freshwater drowning. Although the DI is slightly less specific, it provides valuable complementary information, particularly in cases where pleural fluid assessment is limited.