The use of intravenous catheterisation with a rest period is useful for determination of plasma cortisol levels but not plasma prolactin levels.
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.


METHODS
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 microg/dl at T-15 vs 16.5+/-6.1 microg/dl at T0, P<0.0001), in the UK subgroup (18+/-6.1 microg/dl at T-15 vs 16.6+/-6.4 microg/dl at T0, P=0.0003) but not in men (18+/-4.4 microg/dl at T-15 vs 17.5+/-5.8 microg/dl at T0, P=0.47) and in the K subgroup (17.8+/-4.6 microg/dl at T-15 vs 17+/-5.4 microg/dl at T0, P=0.13). At T0, 3.3% and 15% of patients presented values below the cut-off value of 10 microg/dl (276 nmol/l) and 17 microg/dl (470 nmol/l), respectively.


CONCLUSIONS
These results don't justify intravenous catheterisation with a rest period for plasma prolactin determination in contrast with plasma cortisol determination.
Briet
C
C
Department of Endocrinology, Diabetologia and Nutrition, University Medical Centre, 80054 Amiens cedex 1, France.
Saraval
M
M
Loric
S
S
Topolinski-Duyme
H
H
Fendri
S
S
Desailloud
R
R
D000307:Adrenal Gland Diseases / Q000097:blood / Q000175:diagnosis; D000328:Adult; D001800:Blood Specimen Collection / Q000379:methods*; D002405:Catheterization, Central Venous / Q000379:methods*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010900:Pituitary Diseases / Q000097:blood / Q000175:diagnosis; D011085:Polycystic Ovary Syndrome / Q000097:blood / Q000175:diagnosis; D011388:Prolactin / Q000097:blood*; D015203:Reproducibility of Results; D013997:Time Factors
D011388:Prolactin; D006854:Hydrocortisone