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Immunoluminometric assay of chromogranin A in serum with commercially available reagents
H Bender1, A Maier, B Wiedenmann
1Endocrine Laboratory, Heidelberg, FRG.
Insights
A new immunoluminometric assay (ILMA) accurately measures Chromogranin A (Cg A) in serum. This sensitive and specific assay aids in diagnosing neuroendocrine neoplasia.
Area of Science:
- Biochemistry
- Clinical Chemistry
- Immunology
Background:
- Chromogranin A (Cg A) is a key biomarker for neuroendocrine neoplasia.
- Existing diagnostic methods require improvement in sensitivity and specificity.
Purpose of the Study:
- To develop and validate a novel immunoluminometric assay (ILMA) for serum Cg A measurement.
- To assess the assay's sensitivity, specificity, and dynamic range for clinical application.
Main Methods:
- Utilized a new polystyrene tube with a large surface area, coated with a polyclonal antibody, as the solid phase.
- Employed acridinium ester-labeled monoclonal antibody for detection in a 2-hour incubation step.
- Measured bound luminescence to quantify Cg A levels in patient serum samples.
Main Results:
- The ILMA demonstrated high sensitivity (1 µg/L detection limit) and specificity for human Cg A.
- A wide dynamic range (1–1000 µg/L) was achieved, with a normal range in healthy individuals of 10–53 µg/L (median 30 µg/L).
- Correlations with creatinine and parathyroid hormone, and the impact of calcium injection on Cg A, were investigated.
Conclusions:
- The developed ILMA is a sensitive, specific, and reliable method for quantifying serum Cg A.
- This assay offers significant potential for the diagnosis and monitoring of neuroendocrine neoplasia.
- Further studies explored Cg A correlations and physiological influences, enhancing its clinical utility.
Abstract:
Chromogranin A (Cg A) is a useful marker of neuroendocrine neoplasia in humans. Here we describe an immunoluminometric assay (ILMA) for measuring Cg A in serum, with use of a new tube as a solid phase. The new tube has a large surface area and is coated with a polyclonal antibody. Optimized coating conditions provide a high IgG adsorption to the polystyrene wall. Serum is added to the coated tube and incubated for 2 h or overnight. After washing the tubes, acridinium ester-labeled monoclonal antibody against Cg A is added and incubation is continued for 2 h. The tubes are washed again and the bound luminescence is measured. The assay is very sensitive (detection limit 1 microgram/L, if 25 microL of serum is used), is specific for human Cg A, and offers a wide dynamic range (1-1000 micrograms/L). The range in healthy humans is 10-53 micrograms/L (median 30 micrograms/L). The correlation of serum Cg A to creatinine and parathyroid hormone is described. We also report the influence of intravenous calcium injection on Cg A concentrations in serum.
