Send to

Choose Destination
Clin Chim Acta. 2008 Jan;387(1-2):150-2. Epub 2007 Sep 8.

False positive PTH results: an easy strategy to test and detect analytical interferences in routine practice.

Author information

Department of Clinical Chemistry, University Hospital of Liege, University of Liege, B-35 Domaine du Sart-Tilman, B-4000 Liege, Belgium.



As other immunoassays, PTH determination is not free from interferences. Indeed, natural antibodies like heterophile antibodies (HAMA) and rheumatoid factor (RF) can induce falsely elevated results, leading to misdiagnosis and expensive unnecessary explorations. However, in routine practice, these interferences are not always obvious to detect.


On 2084 PTH samples, we applied a validation strategy in four steps to screen for HAMA and rheumatoid factor interferences.


36% of our samples presented an elevated PTH. We found a clinically plausible reason for 91% of them. The remaining 63 suspicious samples were treated with HBT and 40% of them were found to be HAMA positive. RF determination was performed on the HAMA-negative samples and RF was positive in 21 of them. They were then treated with RF-Absorbent. Nine of these 21 samples presented RF interference.


Applying this strategy in our routine validation, we managed to avoid spuriously elevated PTH results, which could have caused medical errors as well as unnecessary cost-effective extra-investigations.

[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Elsevier Science Icon for ORBi (University of Liege)
Loading ...
Support Center