Intended use

The intended use of these reagents is the determination of chromogranin A in human serum or plasma.

For professional use within a laboratory.

This product is also available as research use only. Product code: RB 321 RUO

For complete product description, claims and use, please refer to the Instructions For Use. Contact your local representative for availability in your country.

Background

Chromogranins and secretogranins constitute a family of uniquely acidic proteins that are co-stored with neurotransmitters and peptide hormones in the brain and the diffuse neuroendocrine system. Structurally these proteins are products of different genes but share some overall properties such as an abundance of acidic amino acid residues and several pairs of basic amino acids as potential positions for post-translational cleavage. Chromogranins are co-stored and co-released with neuropeptides and hormones in the neuroendocrine cells throughout the body. A role for chromogranins in the generation of hormonal granules and package of hormones has been suggested. Furthermore, chromogranins can be cleaved into smaller fragments, which can display biological activities such as inhibition of hormonal release, vasodilatation and anti-microbiological effects.

Tumours of neuroendocrine origin usually present with increased serum/plasma levels of chromogranin A. The neuroendocrine tumours are derived from the neuroendocrine cells and typical neuroendocrine tumours are carcinoid tumours, pheochromocytomas, neuroblastomas, small cell lung cancers, hyperparathyroid adenomas, pituitary tumours, prostate cancers and pancreatic islet tumours and including the MEN1 and MEN2 syndromes. This also includes the different neuroendocrine tumour syndromes, namely the gastrinomas, insulinomas, glucagonomas, somatostatinomas. PPomas and the non-functioning neuroendocrine tumours. For these tumours, chromogranin A has been shown to be the best circulating marker.

The first radioimmunoassay for measurements of chromogranin A was introduced in 1986. Since then other assays for measurements of intact human chromogranin A have been reported. Assays for measurements of defined regions of chromogranin A have also been established, such as specific methods for pancreastatin and other regions of chromogranin A.

The present chromogranin A is a competitive method based on polyclonal antibodies raised in rabbits. The antibodies were raised against a purified fragment containing amino acid sequence 116-439 in the chromogranin A molecule.

Clinical considerations

Tumours of neuroendocrine origin usually present with increased serum/plasma levels of chromogranin A. The neuroendocrine tumours are derived from the neuroendocrine cells.

Typical neuroendocrine tumours are carcinoid tumours, pheochromocytomas, neuroblastomas, small cell lung cancers, hyperparathyroid adenomas, pituitary tumours, prostate cancers and pancratic islet tumours and including the MEN1 and MEN2 syndromes. This also includes the different neuroendocrine tumour syndromes, namely the gastrinomas, insulinomas, glucagonomas, somatostatinomas, PPomas and the non-functioning neuroendocrine tumours.

Reference range, serum: < 3.0 nmol/L.

The reference range was set by testing 127 blood donors (63 men and 64 women, ages 20-68).

The upper range < 3.0 nmol/L was calculated as the 97.5 percentile.

It is recommended that users establish reference ranges for the populations served by their own laboratories.

Non-tumour associated increases of chromogranin A

Increased levels of chromogranin A can be seen in patients with decreased renal function, patients with atrophic gastritis and patients with ongoing treatments with proton-pump inhibitory drugs.

Technical information

The basic principle for determination of chromogranin A with the EURO-DIAGNOSTICA chromogranin A RIA kit is the competitive radioimmunoassay using antibodies against human chromogranin A.

Chromogranin A in standards and samples compete with ¹²⁵I-labelled chromogranin A in binding to the antibodies. The ¹²⁵I-chromogranin A binds to the antibodies in an inverse proportion to the concentration of chromogranin A in standards and samples. Antibody-bound ¹²⁵I-chromogranin A is separated from the unbound fraction using the double antibody solid phase technique. The bound fraction of ¹²⁵I-chromogranin A is measured in a gamma counter.

For professional use within a laboratory.

Kit components and storage of reagents

The reagents provided in each kit are sufficient for 100 tubes.

Composition of the reagent kit

1. Anti-chromogranin A (Reagent A)

Rabbit antiserum to human chromogranin A (amino acids 116-439). The antiserum is diluted  and lyophilized in 2.0 mL 0.25 M phosphate buffer, pH 7.4, with 1.0% bovine serum albumin,

0.375 M NaCl, 0.25% NaN₃ and 2.5% Tween 20.

Colour: Yellow. Reconstitution in 11.0 mL distilled water.

2. ¹²⁵I-Chromogranin A (Reagent B)

Activity: 56 KBq (1.5 μCi) on activity reference date. Lyophilized in 2.5 mL 0.25 M phosphate buffer, pH 7.4, with 1.0% bovine albumin, 0.375 M NaCl, 0.25% NaN₃ and 2.5% Tween 20.

Colour: Blue. Reconstitution in 12.5 mL distilled water.

3. Double antibody solid phase (Reagent C)

Anti-rabbit-Ig coupled to cellulose particles. 52 mL suspension.

4. Assay diluent (Reagent D)

50 mL of 0.05 M phosphate buffer, pH 7.4, with 0.2% bovine serum albumin, 0.075 M NaCl, 0.05% NaN₃ and 0.5% Tween 20. Buffer used for dilution of samples, preparation of working standards and for replacement of antiserum in non-specific binding controls.

5. Chromogranin A standard (Reagent E)

Concentration: 10.0 nmol/L

Volume: 2.00 mL standard after reconstitution.

Lyophilized in 2.00 mL 0.05 M phosphate buffer, pH 7.4 with 0.2% bovine serum albumin,

0.075 M NaCl, 0.05% NaN₃ and 0.5% Tween 20.

Reconstitution in 2.00 mL distilled water.

6. Controls (Reagent F-G)

Lyophilized controls with two different levels of chromogranin A. 1.00 mL of each control after reconstitution. The chromogranin A concentrations are given on the labels of the vials. The controls should not be diluted after reconstitution.

Reconstitution in 1.00 mL distilled water.

Reagent preparation and storage

Store all reagents at 2-8° C before reconstitution and use. The water used for reconstitution of the lyophilized reagents should be distilled in an all-glass apparatus or be of corresponding purity. Dissolve the contents in the vials by gentle inversion and avoid foaming. The stability of the reagents is found on the labels of the vials. For lyophilized reagents the expiry date is valid for the unreconstituted reagents. Reconstituted reagents are stable for 12 weeks