Correlation and comparison of Nb2 lymphoma cell bioassay with radioimmunoassay for human prolactin

Serum samples from groups of men and women with normal and elevated prolactin (PRL) levels were assayed by radioimmunoassay (RIA) and by Nb2 lymphoma cell bioassay (BA) for the presence of PRL. Because the Nb2 lymphoma cells respond to both PRL and growth hormone, BA for PRL activity was carried out before and after neutralization of growth hormone in the serum samples. There were excellent correlations between RIA and BA both in euprolactinemic (r = 0.7587; P less than 0.002) and hyperprolactinemic (r = 0.9558; P less than 0.001) subjects. On an absolute basis, RIA and BA values were similar in the euprolactinemic group (6.6 +/- 0.8 versus 6.2 +/- 1.0), whereas in the hyperprolactinemic group, RIA values were significantly higher than the BA results (89.41 +/- 22.4 versus 62.1 +/- 21.2). The two assay systems also appeared to correlate better in women who were hyperprolactinemic, with obvious menstrual cycle disturbances, than in hyperprolactinemic women without menstrual cycle disturbances.