Pulmonary surfactant-associated protein A as a marker of respiratory distress in forensic pathology: Assessment of the immunohistochemical and biochemical findings

The aim of the present study was to review the immunohistochemical and biochemical findings with reference to the causes of death in routine casework (total, n = 492). In the immunohistochemistry (n = 283), an increase in intra-alveolar granular SP-A (SP-A score) was often observed in asphyxiation (n = 21/34, 61.8%) and freshwater drowning (n = 15/24, 62.5%), and also in fire and methamphetamine (MA) fatalities (n = 22/76, 28.9% and n = 5/16, 31.3%). Serum SP-A level (n = 134) was elevated in acute respiratory distress syndrome and in some cases of drowning, fire and MA fatalities, hyperthermia and chest traumas. A quantitative analysis of SP-A subclass-gene expression (SP-A1/A2 mRNA) in the lung tissue specimens (n = 126) revealed an increase in the SP-A1/A2 mRNA ratio in asphyxiation (n = 17/21, 80.9%), freshwater drowning (n = 7/9, 77.7%), fire and MA fatalities (n = 20/35, 57.1% and n = 8/10, 80.0%). These findings suggested the usefulness of SP-A as a marker of asphyxiation, respiratory distress and alveolar injury.