Hemolysis falsely decreases intraoperative parathyroid hormone levels

Intraoperative parathyroid hormone (IOPTH) measurement is used to confirm biochemical cure during parathyroidectomy. Falsely decreased IOPTH measurements could result in false-negative or false-positive results and lead to failed parathyroidectomy or unnecessary additional exploration.

The records of all patients who underwent parathyroidectomy with IOPTH between May and August 2007 were retrospectively reviewed, and the frequency of hemolysis of IOPTH samples was determined. Separately, 10 split-samples were hemolyzed using the freeze-thaw technique.

Forty-seven patients underwent parathyroidectomy, and 226 IOPTH samples were sent. Seventeen (7.5%) specimens from 9 (18.8%) patients were hemolyzed. In 8 split-samples, the range of decrease caused by hemolysis was 24.5% to 53.8% compared with nonhemolyzed controls.

Hemolysis of IOPTH samples occurs commonly and falsely decreases IOPTH levels. Unrecognized hemolysis in pre-excision specimens could result in false-negative IOPTH results and lead to unnecessary continued exploration. Unrecognized hemolysis in postexcision specimens could lead to false-positive IOPTH results and lead to failed parathyroidectomy and the need for reoperation. Thus, hemolysis may be an easily preventable cause of erroneous IOPTH measurements.