Screening with Metoclopramide Test to Reduce Unnecessary Pituitary Magnetic Resonance Studies in Moderate Hyperprolactinemia.

Background: In prolactinoma diagnosis, current guidelines recommend prolactin (PRL) assessment, considering values exceeding 200 ng/mL highly suggestive of prolactinoma. However, subtler hyperprolactinemia is more common, and to rule out potential prolactinomas, pituitary resonance magnetic imaging (MRI) studies are necessary. These present limitations in terms of availability, costs, and delays in diagnosis. We aimed to evaluate the screening utility of the metoclopramide (MCP) test in identifying patients with moderate hyperprolactinemia for whom MRI studies might be unnecessary.

Methods: We retrospectively selected patients with moderate hyperprolactinemia, with an MCP test and a pituitary MRI within the same assistance, and with no interfering pharmacological treatment. Increases in PRL (ΔPRLMax) and thyrotropin (ΔTSHMax) after MCP infusion were compared according to MRI findings: patients with microadenoma (<10 mm; n = 23), with macroadenoma (≥10 mm; n = 5), or without adenoma (n = 39).

Results: ΔPRLMax exceeds baseline PRL capability to identify patients with an adenoma (area under the curve = 0.872 vs 0.776). ΔPRLMax below 220% identifies 100% of these patients with 71% of specificity. This screening would have avoided 42% of MRI, resulting in a cost savings of 34%. Analysis of ΔTSHMax only slightly increased specificity when considered as a secondary criterion. Test duration can be shortened to 30 min without compromising its screening capability.

Conclusions: A short MCP test is a useful and cost-effective screening tool to avoid unnecessary MRI. Its simplicity allows its performance in almost any clinical facility to easily rule out prolactinoma in an important percentage of patients, something of upmost importance especially in regions where MRI facilities or their access are limited.