Radioimmunoassay for the measurement of thrombospondin in plasma and breast cyst fluid: validation and clinical application

Thrombospondin is an adhesive protein that has been implicated in malignanc y, specifically in tumour progression and angiogenesis. We developed a radi oimmunoassay for the measurement of thrombospondin in plasma and breast cys t fluid. The assay exhibited high accuracy, with recoveries of 102-136% and acceptable imprecision, with an intra-assay coefficient of variation (CV) of <75% across the analytical range 30-1000 ng/mL and inter-assay CV of 4.4 % and 7.7% at 152 and 224 ng/mL, respectively. Thrombospondin measured in t he breast cyst fluid of patients with gross cystic disease of the breast sh owed that patients with type II (Na+) cysts had significantly higher concen trations than type I (K+) cysts. The plasma thrombospondin reference range was determined as 131-274 ng/mL. Patients with breast cancer had significan tly higher plasma thrombospondin concentrations than normal individuals or patients with benign breast disease. Plasma thrombospondin was higher in br east cancer patients with lymph node involvement.