Interference With VIP to Distinguish Between Real and False VIPoma: National Study From the French Endocrine Tumors...

Area of Science:

• Endocrinology
• Clinical Chemistry
• Oncology

Background:

• Vasoactive intestinal peptide (VIP)-secreting tumors (VIPomas) are rare neuroendocrine tumors.
• Elevated plasma VIP levels confirm diagnosis, but radioimmunoassay (RIA) can be subject to analytical interference.
• Interference can lead to false-positive results, complicating diagnosis and management.

Purpose of the Study:

• To develop and validate laboratory techniques for detecting interference in VIP RIA assays.
• To differentiate between true VIP elevation and interference in patients with suspected VIPomas.

Main Methods:

• Three techniques were employed: RIA with Sephadex column chromatography, RIA with polyethylene glycol precipitation, and a 125I-labeled VIP binding test.
• Patients with suspected false-positive VIP elevation (FPV) were compared with those with proven VIPomas (RV).

Main Results:

• Interference was detected in all FPV patients (n=15) but none of the RV patients (n=9).
• VIP concentrations were significantly higher in FPV patients (228 pmol/L) than RV patients (66 pmol/L).
• The 125I-labeled VIP binding test showed excellent diagnostic performance with a 20.5% threshold (100% sensitivity, 100% specificity).

Conclusions:

• Three novel laboratory techniques effectively identify interference in VIP RIA assays.
• These methods are essential for accurate VIPoma diagnosis when clinical presentation and lab results are discordant.
• Implementing these techniques improves diagnostic reliability for VIP-secreting tumors.