Abstract

Hyperprolactinemia is a prevalent endocrine disorder affecting the hypothalamic-pituitary axis. Immunological assays can yield false-low results in hyperprolactinemia due to the high dose hook effect. To counteract this, dilutions are often employed, but potential errors introduced by this process necessitate a thorough validation of the dilution protocol to ensure result accuracy. This study aimed to compare serum prolactin levels in patients with suspected hyperprolactinemia with and without dilution. Materials and Methods: In this validation study, we analysed serum prolactin levels directly and after 1:10, 1:100, and 1:1000 serial dilutions in 30 patient samples with suspected hyperprolactinemia. A two-proportion Z test was conducted to compare the variation in prolactin levels between different dilution methods and the direct method. Results and Conclusions: Our study revealed that a 1:10 dilution did not significantly alter the prolactin estimate. Higher dilutions of 1:100 and 1:1000 were explored, but no significant difference was observed between the two. Notably, 100% of results were obtained with a 1:100 dilution. In conclusion, sample dilution proves to be a straightforward method for detecting falsely low concentrations, with the 1:100 dilution being particularly effective in mitigating the high dose hook effect. While modern assays have enhanced reliability, physicians should remain vigilant about the high-dose hook effect and consider appropriate sample dilution techniques when necessary.

Description