Parathyroid hormone measurement using a rapid-clotting blood collection tube

Abstract

For parathyroid hormone (PTH) measurement, serum and plasma are used as specimens. When serum was used as a specimen, we found a case that showed a lower measured PTH level than when EDTA-2Na plasma was used. Therefore, the reason for the decrease in the measured PTH level was determined. Using specimens collected from 10 healthy adults, we analyzed the effects of the following on the measured whole PTH level: the type of blood collection tube used, the drug added to the blood collection tube, the number of times a specimen was transferred to a sample cup, the contact area between the sample and the sample tube, and the material of the sample tube. When using a rapid-clotting blood collection tube, the measured whole PTH level was significantly lower than that when using other types of blood collection tubes. Since thrombin decreased the measured whole PTH level in a concentration-dependent manner, the measured whole PTH level was considered to be decreased by thrombin added to the rapid-clotting blood collection tube. Depending on the number of times a specimen was transferred to a sample cup and the contact area between the specimen and the sample tube, the measured whole PTH level decreased. This result suggests that PTH was adsorbed to the plastic tube. Furthermore, the rate of decrease in the measured whole PTH level varies depending on the material of the sample tube, and in the specimen used, i.e., serum or EDTA-2Na plasma. A difference in the rate of decrease with respect to the sample tube of the same material was recognized.