Radioimmunoassay of prolactin in blood spotted on filter paper

In this method for estimating prolactin, 50 microL of whole blood obtained by finger puncture is spotted onto filter paper and blood-spot samples are "punched out" with a 3-mm (diameter) paper punch. The blood is extracted with aqueous buffers and the prolactin measured in large batches by radioimmunoassay. Results were identical with those for prolactin in serum. Prolactin in blood spots is stable at room temperature for up to one week and for several months at -20 degrees C. This simple technique for obtaining blood samples for prolactin estimation has particular potential for field studies of lactating women.