Performance of low-dose cosyntropin stimulation test handled via plastic tube.

PURPOSE: Studies on 1 μg low-dose test showed that among 1 μg cosyntropin samples pushed through long IV plastic tubing, some adrenocorticotropic hormone dosage was not recovered, and in healthy volunteers it provided subnormal cortisol responses. The aim of the current study is to assess whether there is any loss in adrenocorticotropic hormone 1-24 concentration when pushed through a short plastic tube, and to assess serum and salivary cortisol responses in low-dose test among healthy volunteers, using a similar short plastic tube vs. direct intravenous consyntropin injection.

METHODS: We evaluated in vitro if adrenocorticotropic hormone was absorbed in a 2.5 cm plastic tube by measuring adrenocorticotropic hormone 1-24 concentration in a 1 μg/ml adrenocorticotropic hormone aliquot solution before and after being flushed through the plastic tube. For the in vivo study, we recruited 20 healthy adult volunteers. Each subject underwent low-dose test via 2.5 cm plastic tube via plastic tube and via direct intravenous injection by a metal syringe via direct intravenous injection, and cortisol responses were determined.

RESULTS: Mean adrenocorticotropic hormone 1-24 concentration did not differ significantly when flushed via plastic tube or measured in the aliquot solution (P = 0.25). In vivo, mean 30-min serum cortisol concentrations were 20.47 ± 2.87 and 21.62 ± 3.89 μg/dl in via plastic tube and in via direct intravenous injection tests, respectively, and did not show a significant difference (P = 0.16).

CONCLUSIONS: In low-dose test, using a 2.5 cm plastic tube ensures completeness of the intravenous adrenocorticotropic hormone injection dosage and provides equivalent cortisol responses.