La pose d’un cathéter intraveineux associée à une période de repos est utile pour le dosage du cortisol mais ne l’est pas pour le dosage de la prolactine

Abstract

Objective The use of an intravenous catheter with a rest period has been recommended to avoid false-positive results for hyperprolactinaemia and false-negative results for hypocortisolaemia. We tested the relevance of this recommendation. Design Plasma cortisol and prolactin levels were determined before (T-15) and after a 15-min rest period (T0) in 119 patients, 38 males (M) and 81 females (F). 52 of the 119 patients were known (K; 30 females and 22 males) and 67 unknown (UK; 49 females and 18 males) to the unit. Results Prolactin was lower after rest in women (12.3 ± 22.7 ng/l vs 11.7 ± 22.5 ng/ml, P = 0.03), but not in men (6.2 ± 4.5 ng/ml at T-15 vs 5.8 ± 3.2 ng/ml at T0, P = 0.09), in the UK subgroup (10.6 ± 20.7 ng/ml at T-15 vs 10.1 ± 20.9 ng/ml at T0, P = 0.06) and in the K subgroup (10.1 ± 16.7 ng/ml at T-15 vs 9.7 ± 15.8 ng/ml at T0, P = 0.08). None of the patients with prolactin levels higher than 20 ng/ml at T-15 diminished its prolactin value below this cut-off value. Plasma cortisol levels were lower after rest in women (17.9 ± 5.9 μg/dl at T-15 vs 16.5 ± 6.1 μg/dl at T0, P < 0.0001), in the UK subgroup (18 ± 6.1 μg/dl at T-15 vs 16.6 ± 6.4 μg/dl at T0, P = 0.0003) but not in men (18 ± 4.4 μg/dl at T-15 vs 17.5 ± 5.8 μg/dl at T0, P = 0.47) and in the K subgroup (17.8 ± 4.6 μg/dl at T-15 vs 17 ± 5.4 μg/dl at T0, P = 0.13). At T0, 3.3% and 15% of patients presented values below the cut-off value of 10 μg/dl (276 nmol/l) and 17 μg/dl (470 nmol/l), respectively. Conclusion These results don’t justify intravenous catheterisation with a rest period for plasma prolactin determination in contrast with plasma cortisol determination.