ImmunoCAP ECP measures the level of Eosinophil Cationic Protein (ECP) in serum. Eosinophils are the cells chiefly responsible for producing the inflammation associated with asthma. When eosinophils in the airway are activated, they undergo degranulation causing airway epithelial damage. This can lead to chronic inflammatory disease of the airway.
Asthmatic patients with eosinophilic inflammation have elevated levels of ECP in serum and other body fluids such as bronchial alveolar fluid and (induced) sputum. A high level of serum ECP indicates inflammation, which is a risk factor for asthmatic patients.
Asthma therapy consists of suppressing chronic and persistent airway inflammation. Measuring ECP in a serum sample is an objective and direct way of estimating the severity of the airway inflammation and following the course of the disease.
ECP serum measurements can be used:
- For monitoring inflammation in asthma
- For guiding corticosteroid treatment in asthma
- To find non-compliant patients
Expected test values
Normal adult values show a geometric mean of 5.5 µg/l and a 95th percentile of 13.3 µg/l. Values over 15 µg/l should be considered elevated. However, patients should be their own control during treatment follow-up.
Specimen collection and preparation
It is recommended that each laboratory establishes its own procedure for serum sampling. Parameters such as blood collection tube, coagulation time and temperature must be kept within specified limits, since they affect the concentration of released ECP in serum samples. The clotting is an important step of the process. During this process ECP is released by the eosinophils that are activated by the inflammation.
- Collect blood by venipuncture using a serum-gel tube with clot activator. It is important that the tube is completely filled.
- After collection, gently invert the tube several times. Do not shake or vortex the tube.
- Release ECP by clotting for 60 to 120 minutes at room temperature 20-24 °C. The temperature must not vary more than ±1 °C between sampling occasions to give comparable and reproducible results.
- Centrifuge at 1000–1300 x g for 10 minutes at room temperature.
- Decant serum into a new tube.
- Serum samples may be kept at room temperature for shipping purposes. Otherwise store at 2 °C to 8 °C if assayed within five days after collection or at –20 °C if assayed later.
Note: Plasma and haemolyzed serum can not be used. For further reading on interfering substances, please see directions for use.
Preparation of samples
Sample dilution is usually not required. For determination of values higher than 200 μg ECP/l, dilute the samples with ImmunoCAP IgE/ECP/Tryptase Sample Diluent.
Handling of control specimen
It is recommended to remove and recap the control vials from the instrument as soon as the pipetting of the samples is finished and the sample incubation is started. It is also recommended to gently stir the vial before use. ImmunoCAP ECP Control should be treated in the same way as a patient sample in the procedure.