Diagnostic significance of surfactant proteins A and D in sera from patients with radiation pneumonitis

Radiation pneumonitis (RP) is the most common complication of radiotherapy for thoracic tumours. The aim of this study was to evaluate the significanc e of pulmonary surfactant proteins (SP)-A and SP-D as new serum markers for RP. Twenty-five patients with lung tumour, who had received radiotherapy, were studied. At the completion of radiotherapy, the presence of RP was judged by chest p lain radiography and chest high resolution computed tomography (HRCT). RP findings detected on chest plain radiography were seen in only three of 12 patients in whom RP was detected by HRCT. Nevertheless, both SP-A and SP -D concentrations in sera from the patients with RP were significantly high er than those from the 13 patients without RP (p =0.0065, p = 0.0011, respe ctively). As with SP-A, ratios of SPD at the completion, compared to at the initiation (1 week post/pre ratio), were also significantly higher in pati ents with RP than in patients without RP. When a post/pre ratio > 1.6 was c onsidered positive, the SP-A and SP-D assays showed an 83% and 85% specific ity, respectively. In conclusion, serum assays of surfactant proteins A and D may be of diagno stic value for detection of radiation pneumonitis, even when the radiograph ic change is faint.