Procalcitonin interference in an immunometric calcitonin assay

Area of Science:

• Biochemistry
• Clinical Chemistry
• Immunology

Background:

• Procalcitonin (PCT) is elevated in sepsis patients.
• Calcitonin (CT) levels also increase in sepsis.
• Immunoassay methods for CT determination may be affected by PCT.

Purpose of the Study:

• To compare calcitonin (CT) determination using polyclonal and monoclonal antibodies in septic patients.
• To investigate the interference of procalcitonin (PCT) on CT measurements.
• To evaluate the accuracy of different immunoassay methods in the presence of elevated PCT.

Main Methods:

• Analyzed 34 patients (17 septic, 17 non-septic).
• Measured CT using polyclonal (IRMA) and monoclonal (ELISA) antibody-based immunoassays.
• Performed interference and dilution tests using PCT calibrators.

Main Results:

• Polyclonal antibody (IRMA) showed significant PCT interference in septic patients (24.1-718 μg/L), proportional to PCT levels (r = 0.814).
• Monoclonal antibody (ELISA) demonstrated no PCT interference, with CT levels < 6.5-46.3 ng/L.
• Non-septic patients showed no PCT interference with either method.

Conclusions:

• Procalcitonin (PCT) significantly interferes with calcitonin (CT) determination using polyclonal antibodies (IRMA) in septic patients.
• Monoclonal antibody-based assays (ELISA) provide accurate CT measurements, unaffected by PCT.
• ELISA method using monoclonal antibodies is recommended for reliable CT assessment in sepsis.