Role of prolactin/adenoma maximum diameter and prolactin/adenoma volume in the differential diagnosis of prolactinomas and other types of pituitary adenomas.

The present study aimed to investigate the function of the prolactin/adenoma maximum diameter (PRL/MD) and the prolactin/adenoma volume (PRL/V) in the differential diagnosis of prolactinomas and other types of pituitary adenomas. A total of 118 patients with pituitary adenoma, hyperprolactinemia and a plasma PRL <250 µg/l were enrolled. Clinical data from these patients were retrospectively analyzed. A receiver operating characteristic curve was plotted. The function of PRL, PRL/MD and PRL/V in the differential diagnosis of prolactinomas and other types of pituitary adenomas was compared. The results revealed that a PRL of 55.65 µg/l was the most accurate [sensitivity (SE), 0.800; specificity (SP), 0.716; positive predictive value (PPV), 0.857; negative predictive value (NPV), 0.933; and Youden index (YI), 0.516]. The PRL/MD with the highest diagnostic value was 4.03 µg/(l × mm) (SE, 0.800; SP, 0.898; PPV, 0.727; NVP, 0.929; and YI, 0.698). The PRL/V with the highest diagnostic value was 54.00 µg/(l × cm3) (SE, 0.900; SP, 0.966; PPV, 0.900; NVP, 0.966; and YI, 0.866). The PRL/MD tended to be of higher diagnostic accuracy than PRL, but this difference was not statistically significant (P=0.097). The differentiation ability of PRL/V was significantly stronger than that of PRL (P=0.028). Thus, serum PRL, PRL/MD and PRL/V levels may be able to differentiate prolactinomas from other types of hyperprolactinemia-causing pituitary adenomas prior to treatment. PRL/V may be better than the PRL level in achieving a differential diagnosis, and the optimal PRL/V ratio for differentiating prolactinomas from other types of hyperprolactinemia-causing pituitary adenomas was 54.00 µg/(l × cm3).