A cannulated prolactin series reduces the need for further investigations in women with infertility and lowers the number of false positive screening prolactin measurements

Abstract

Background:The prevalence of hyperprolactinaemia in women presenting for infertility investigation has been found to be up to 17%, and many of these women are asymptomatic. Prolactin levels may be elevated by stress, including phlebotomy and not be of clinical significance. A cannulated prolactin study may be a useful way to discriminate this. Aim:To determine the utility of a cannulated prolactin series in women presenting with infertility who have a raised prolactin measurement at referral for first fertility consultation. Materials and Methods:All women referred to two fertility centres had a prolactin level measured prior to first appointment over a two-year period. If the level remained elevated on the second measure after macroprolactin precipitation, women were referred for a cannulated prolactin series. If the prolactin concentration fell within the reference range during the series then the result was regarded as normal.Results: Forty-four (2.7%) of 1660 women seen for a first specialist appointment had persistently raised prolactin concentrations after two samples and were referred for a cannulated series. The proportion of women whose prolactin was found to be normal during the cannulated prolactin series was 61% (95% CI 47-74%). Even in patients with a referral prolactin of greater than 1000 mU/L, 45% had a normal two-hour cannulated series. Conclusion:A high proportion (61%) of women with raised prolactin at time of referral for first specialist appointment had a normal prolactin after a two-hour cannulated series. A cannulated prolactin study can avoid unnecessary further investigations in these women.

The utility of rested prolactin sampling in the evaluation of hyperprolactinaemia

“…5 Other studies investigating serial sampling over 120 min include a study of 42 (88% female) patients where random (nonrested) prolactin was elevated on more than one occasion, in which normalisation occurred in 12 cases (29%), 6 and a study of 44 women specifically referred for fertility assessment, in which normalisation occurred in 27 cases (61%). 7 The latter study specifically commented that all patients with a normal prolactin at any time during serial sampling had a normal prolactin at the end of serial sampling, consistent with our finding that a single rested sample is equally effective as serial sampling. Macroprolactin interference and use of medications associated with hyperprolactinaemia were systematically excluded in all three studies.…”

“…A study of 235 (92% female) patients undergoing serial prolactin sampling identified normalisation of the initial prolactin in 41 cases (17%) and normalisation on repeat sampling in 23 of the remaining 194 cases (12%), with repeat sampling obtained after 120 min 5 . Other studies investigating serial sampling over 120 min include a study of 42 (88% female) patients where random (nonrested) prolactin was elevated on more than one occasion, in which normalisation occurred in 12 cases (29%), 6 and a study of 44 women specifically referred for fertility assessment, in which normalisation occurred in 27 cases (61%) 7 . The latter study specifically commented that all patients with a normal prolactin at any time during serial sampling had a normal prolactin at the end of serial sampling, consistent with our finding that a single rested sample is equally effective as serial sampling.…”

“…Normalisation with serial sampling has been reported in patients with an initially elevated serum prolactin level. [5][6][7][8][9][10][11] However, the rationale for obtaining multiple samples is unclear. We hypothesised that the use of the final, 'most rested' sample would be sufficient to minimise the impact of venepuncture stress.…”

“…Our protocol is to obtain three samples from an indwelling cannula over a 40‐min period (0, 20 and 40 min). Normalisation with serial sampling has been reported in patients with an initially elevated serum prolactin level 5–11 . However, the rationale for obtaining multiple samples is unclear.…”

Diagnostic Utility of the Prolactin Decrease Rate in the Diagnosis of Mild Hyperprolactinemia

“…Tsur et al [13] found that it PRL returned to normal at 60 min in 86 patients (24%) and at 90 min in 87 patients (24.2%); thus, prolonging the test period did not signi cantly contribute to the diagnostic process. Meanwhile, previous studies have stated that stress-related PRL elevation stems from a fear of blood drawing [7,14]. However, the stress-related PRL elevation results in previous studies were similar to that of the present study, which examined blood samples taken using the venous puncture method, suggesting that PRL elevation may be independent of a fear of venous puncture.…”