Postmortem serum levels of pulmonary surfactant-associated proteins A and D with regard to the cause of death in medicolegal autopsy.

Pulmonary surfactant-associated proteins A and D (SP-A and -D) are tissue-specific components. Previous studies showed an increase in the postmortem serum SP-A level due to acute pulmonary alveolar damage and acute respiratory distress. The present study comparatively investigated serum SP-A and SP-D levels with regard to the cause of death in serial medicolegal autopsy cases (n=679, within 48 h postmortem). SP-A and SP-D levels were usually higher in left cardiac blood than at other sites, independent of postmortem interval. The left-to-right difference was significantly larger for mechanical asphyxiation, drowning, intoxication and spontaneous cerebral hemorrhage. Both SP-A and -D levels in bilateral cardiac blood were significantly higher for drowning and secondary pulmonary damage involving ARDS after traumas, but were lower for hypothermia (cold exposure). SP-A was predominantly elevated in fire fatality and delayed deaths from injury and fires, while pneumonia showed a predominant elevation of SP-D. These findings suggest that comparative analysis of serum SP-D and SP-A is useful for investigating primary or secondary pulmonary alveolar damage in the death process.